1963 Imperial - Bulkhead Connection and Alternator Upgrade - Please help me understand?

[UGW]

Background

Like the title says, I have a 1963 Imperial Custom that's pretty much stock. It has a dealer-installed Mopar AC from the 1960s, and I have added a CD player, some modern aux gauges, and a 3rd/center mount brake light. The AC is wired into the back of the fuse block, as was standard procedure. The radio and gauges have their own fuses, 15A for the radio, 5A for gauges, and are also tapped into the fuse block. The brake light is tapped into the existing brake circuit, which is already protected.

In the future, I'd like to add an electric radiator fan, because even my 7-blade fan with no clutch can't keep up in traffic on these 95 degree days. My plan is to connect the fan using a relay with integrated fuse straight from the battery or starter relay, so that only the signal wire (low current) runs into the passenger cabin for a manual switch, thus reducing current in the wire harness. (I believe this is how the factory horns work, if I am reading the manual wiring diagram correctly?) Some day, I'd also love to add a small, 30A powered subwoofer, but that is a long way off.

My alternator has a 1963 date stamped on it, so (according to the service manual) it's at most 39 amps if it was upgraded with the AC, or 35 amps if it wasn't. In a way, I suppose this is good because the alternator physically can't produce enough current to cause trouble. However, it also struggles to keep the battery charged on a hot, rainy day, when I'm running my headlights, wipers, and AC together, in town traffic below 30mph. It also doesn't always fully recharge my battery on short trips, which is most of my driving.

The Problem

I'd like to upgrade my alternator. It doesn't need to be crazy - even the 60A units Rockauto specifies for this car would be a major improvement.

Now, I've read the MAD Electrical article, which some people love, and some hate. I've read lots of posts on this forum and others. I've watched @72RoadRunnerGTX 's videos about the dangers of a bypass. The last thing I want is to set my car on fire. (Which is why everything I've added so far has a dedicated fuse.) However, I'm more confused if anything.

1. Does that MAD article even apply to me? 1963 has the screw-type connectors (picture below), which I've read are superior to the packard/delphi 56 terminals most articles reference. Unfortunately, most articles aren't aimed at early 60s Imperials, but later Chargers, trucks, etc, so information is scarce.
2. I'm ok with bypassing my ammeter. One of my aux gauges is a voltmeter, so I would still have eyes on my charging system.
3. The connections on the back of my ammeter also look very good to me. I did the RTE solid-state volt limiter upgrade on my gauge power last summer, and everything looks remarkably clean.

My bulkhead connector, for reference, power terminal circled. I know it looks a bit grungy, someone went crazy with the Ziebart on this car at some point.

And here is the inside, so you can see the general condition:

Do I need to modify my wiring to upgrade my alternator?

Second question: Instead of a bypass from the alternator to the starter, what if I just made a jumper wire from the red to black terminals, inside the engine bay?
I haven't seen anyone mention this, so maybe it's a bad idea? My thinking is that this would prevent excess current from going into the dash by providing a second pathway to the battery, but it would still be a single pathway, which would preserve the utility of the fusible link at the starter relay? I suppose maybe this does not help if the factory red & black wires aren't up to the task? Or maybe the bulkhead terminals themselves would still overheat?


Here's an example of what I was thinking. (Black terminal is obscured by 6-pin connector above it)

Anyway, really would like some advice here. I'm no electrical engineer.

Finally, here's the wiring diagram if it helps anyone:

 

[Big_John]

1. Does that MAD article even apply to me? 1963 has the screw-type connectors (picture below), which I've read are superior to the packard/delphi 56 terminals most articles reference.

No it doesn't. If you look at 65(?) and earlier cars, they have that nice screw connection. Just make sure it's clean.

@72RoadRunnerGTX will probably be along to answer more questions. Watch some of his other videos though. Time well spent.

 

[72RoadRunnerGTX]

Background

Like the title says, I have a 1963 Imperial Custom that's pretty much stock. It has a dealer-installed Mopar AC from the 1960s, and I have added a CD player, some modern aux gauges, and a 3rd/center mount brake light. The AC is wired into the back of the fuse block, as was standard procedure. The radio and gauges have their own fuses, 15A for the radio, 5A for gauges, and are also tapped into the fuse block. The brake light is tapped into the existing brake circuit, which is already protected.

In the future, I'd like to add an electric radiator fan, because even my 7-blade fan with no clutch can't keep up in traffic on these 95 degree days. My plan is to connect the fan using a relay with integrated fuse straight from the battery or starter relay, so that only the signal wire (low current) runs into the passenger cabin for a manual switch, thus reducing current in the wire harness. (I believe this is how the factory horns work, if I am reading the manual wiring diagram correctly?) Some day, I'd also love to add a small, 30A powered subwoofer, but that is a long way off.

My alternator has a 1963 date stamped on it, so (according to the service manual) it's at most 39 amps if it was upgraded with the AC, or 35 amps if it wasn't. In a way, I suppose this is good because the alternator physically can't produce enough current to cause trouble. However, it also struggles to keep the battery charged on a hot, rainy day, when I'm running my headlights, wipers, and AC together, in town traffic below 30mph. It also doesn't always fully recharge my battery on short trips, which is most of my driving.

The Problem

I'd like to upgrade my alternator. It doesn't need to be crazy - even the 60A units Rockauto specifies for this car would be a major improvement.

Now, I've read the MAD Electrical article, which some people love, and some hate. I've read lots of posts on this forum and others. I've watched @72RoadRunnerGTX 's videos about the dangers of a bypass. The last thing I want is to set my car on fire. (Which is why everything I've added so far has a dedicated fuse.) However, I'm more confused if anything.

1. Does that MAD article even apply to me? 1963 has the screw-type connectors (picture below), which I've read are superior to the packard/delphi 56 terminals most articles reference. Unfortunately, most articles aren't aimed at early 60s Imperials, but later Chargers, trucks, etc, so information is scarce.
2. I'm ok with bypassing my ammeter. One of my aux gauges is a voltmeter, so I would still have eyes on my charging system.
3. The connections on the back of my ammeter also look very good to me. I did the RTE solid-state volt limiter upgrade on my gauge power last summer, and everything looks remarkably clean.

My bulkhead connector, for reference, power terminal circled. I know it looks a bit grungy, someone went crazy with the Ziebart on this car at some point.


And here is the inside, so you can see the general condition:


Do I need to modify my wiring to upgrade my alternator?

Second question: Instead of a bypass from the alternator to the starter, what if I just made a jumper wire from the red to black terminals, inside the engine bay?
I haven't seen anyone mention this, so maybe it's a bad idea? My thinking is that this would prevent excess current from going into the dash by providing a second pathway to the battery, but it would still be a single pathway, which would preserve the utility of the fusible link at the starter relay? I suppose maybe this does not help if the factory red & black wires aren't up to the task? Or maybe the bulkhead terminals themselves would still overheat?


Here's an example of what I was thinking. (Black terminal is obscured by 6-pin connector above it)


Anyway, really would like some advice here. I'm no electrical engineer.

Finally, here's the wiring diagram if it helps anyone:

From what I’ve read of your scenario I would have to agree with @Big_John, the Mad approach is not warranted at all. That Mad article specifically states it addresses the bulkhead Packards and the later seventies plastic framed trunk ammeter fiasco. Much of the issues described in that article were created by mis-loading this charging system, heavy loads at the battery. Many wrongly conflate the information presented to apply to any Chrysler ammeter-based charging system. Yes, the earlier screw terminal bulkhead pass-throughs can handle much more current than the later Packards, just did not suffer the same failure rates the later cars did. For the mentioned stock loading, with good ammeter connections as described, jumping the bulkhead terminals as pictured will gain you little. Won’t hurt anything but will disable the ammeter’s function. For those that believe that simply having the ammeter wires connected to the ammeter exposes the car to the dreaded mythical “spontaneously combusting ammeter” syndrome, that by-pass will not alleviate that fear. Sarcasm, if it’s not clear.

As for the planned added/non-stock loads mentioned, take that power off the alternator, not the battery or starter relay if you don’t want to add that current to your stock wiring. Try to run an alternator with the capacity to cover any and all loads that will be running at the same time while the charging system is operating. Any current draw the alternator can’t cover will then be pulled from the battery across the stock wiring.

There are several other videos on that channel where I go into detail on the safe way to load this system. Mainly about the later system where the Packards in the charging system is by far the weakest link, any mention of those Packards again would not apply to the screw terminal pass-though you are running stock loads through. However, be careful when adding loads, load placement still matters.

Older video on load placement matters, I think I specifically example adding cooling fans.

 

[UGW]

As for the planned added/non-stock loads mentioned, take that power off the alternator, not the battery or starter relay if you don’t want to add that current to your stock wiring. Try to run an alternator with the capacity to cover any and all loads that will be running at the same time while the charging system is operating. Any current draw the alternator can’t cover will then be pulled from the battery across the stock wiring.

There are several other videos on that channel where I go into detail on the safe way to load this system. Mainly about the later system where the Packards in the charging system is by far the weakest link, any mention of those Packards again would not apply to the screw terminal pass-though you are running stock loads through. However, be careful when adding loads, load placement still matters.

Wow, thank you SO MUCH, @72RoadRunnerGTX and @Big_John ! This community is great.

I was thinking as I ate dinner tonight that running the fans from the starter relay would be a bad idea, exactly as you described: all the fan current would have to flow through the dash harness before it reached the fans, which is exactly what I don't want.

If I connect the fans upstream of the alternator-side terminal, then the fan current branches off before it reaches the bulkhead, is that right? I think this would have the added benefit of swinging the ammeter needle toward "discharge" if the fans pull more current than the alternator can supply. Of course, if I ran the fans with the engine off everything is reversed, but there's not much reason to do that.

Help me understand one more thing: Say I installed a 100A alternator, and connect any new accessories to the alternator (maybe using a dedicated fuse block for distribution) when none of those accessories are running, would all the excess amperage run through the stock harness to the battery? Or does the alternator only generate what is needed? (My understanding of this part of the charging system is not great.)

Finally, for my interior accessories (radio, gauges) I just wanted to mention I connected them downstream of the factory fuses. Even though they're fairly low draw, this way the existing protection should function as designed if they start pulling too much combined with what's already on the circuit.

 

[72RoadRunnerGTX]

Wow, thank you SO MUCH, @72RoadRunnerGTX and @Big_John ! This community is great.

I was thinking as I ate dinner tonight that running the fans from the starter relay would be a bad idea, exactly as you described: all the fan current would have to flow through the dash harness before it reached the fans, which is exactly what I don't want.

If I connect the fans upstream of the alternator-side terminal, then the fan current branches off before it reaches the bulkhead, is that right? I think this would have the added benefit of swinging the ammeter needle toward "discharge" if the fans pull more current than the alternator can supply. Of course, if I ran the fans with the engine off everything is reversed, but there's not much reason to do that.

Help me understand one more thing: Say I installed a 100A alternator, and connect any new accessories to the alternator (maybe using a dedicated fuse block for distribution) when none of those accessories are running, would all the excess amperage run through the stock harness to the battery? Or does the alternator only generate what is needed? (My understanding of this part of the charging system is not great.)

Finally, for my interior accessories (radio, gauges) I just wanted to mention I connected them downstream of the factory fuses. Even though they're fairly low draw, this way the existing protection should function as designed if they start pulling too much combined with what's already on the circuit.

Alternators are rated by their output capacity limit, they don’t push current. Any current flowing out of the alternator is determined by the load drawing the current. No changes to the loading, there won’t be additional current flowing. If you place your high current fans taking power off the alternator stud and the alternator can cover that load and the stock loads, there will be no impact to the stock system while the engine is running. As mentioned, engine off, the battery becomes the power source these added loads will pull its current across the stock wiring, to be avoided. The regulator simply throttles the alternator to cover whatever the demand is, no more, to the limit of what it can be produce. The biggest advantage to running bigger alternators with somewhat stock loads is more available current at idle over stock sized alternators.



The stock fuse box is correctly loaded, anything added to the stock fuse box will not impact the system unless it draws significant current. Doesn’t sound like there is anything to be concerned with on that.

 

[UGW]

Thanks!

Probably overkill, but it makes me wonder about putting something like this 150A relay between an upgraded alternator, and the auxiliary loads.

If you could find a signal circuit that only had power when the engine was running, you could activate the relay, and the alternator would send power to the second circuit. But, if the engine was off, the relay would open, and battery power would never flow to the auxiliary load.

https://www.bluesea.com/products/7765/Solenoid_L-Series_-_150A_12_24V

 

[72RoadRunnerGTX]

Thanks!

Probably overkill, but it makes me wonder about putting something like this 150A relay between an upgraded alternator, and the auxiliary loads.

If you could find a signal circuit that only had power when the engine was running, you could activate the relay, and the alternator would send power to the second circuit. But, if the engine was off, the relay would open, and battery power would never flow to the auxiliary load.

https://www.bluesea.com/products/7765/Solenoid_L-Series_-_150A_12_24V

Engine running or not? I would add an oil pressure switch to activate your relay, pretty easy and cheap. Get the original oil pressure switch voltage signal from igniton1, if the key is powered up with no oil pressure, no relay operation.
Would have to agree, that particular relay may be a little much.

 

[UGW]

Engine running or not? I would add an oil pressure switch to activate your relay, pretty easy and cheap. Get the original oil pressure switch voltage signal from igniton1, if the key is powered up with no oil pressure, no relay operation.
Would have to agree, that particular relay may be a little much.

Oh, now that is brilliant! The B/RB block even has a second port on the passenger side. A bonus would be that if all your accessories suddenly quit, you know you've lost oil pressure

I doubt I'll ever get that far, but having an isolated accessory circuit that completely preserves the factory wiring seems like such a cool idea. It definitely makes everything harder, but I enjoy the challenge of designing all my modifications so that they can be easily reversed, without a trace.

Thanks so much for indulging my curiosity.

 

[UGW]

I'm still puzzling this in the background. Would something like this work?
- connect high-amp alternator and auxiliary fuse block to same terminal of a "maxi" fuse block, or breaker, with nice, thick wire
- connect original alternator wire to the other fuse terminal
- install 40A fuse, since original alternator was rated 39A

This way, the new, modern wiring can pull all the current it wants, but the original circuit is still capped at the factory max. Whether the current comes from the battery or the alternator doesn't matter, because the fuse isn't directional.

Battery current would still run through the dash, but my hope is the fuse would kick in before things got too hot. (I could connect another, identical fuse on the battery side of the bulkhead, unsure if it's needed?)

The other downside here is that if I blew the fuse while driving, I think the car might shut off? But, that's not any different than if I burned up my wiring, and much easier to repair on the roadside!

https://www.bluesea.com/products/5006100/MAXI_Fuse_Block

 

[slantsixdan]

The AC is wired into the back of the fuse block

Do yourself and your car a large favour: install an A/C compressor clutch relay, so the switches in the A/C unit only have to cope with the few milliamps of current a relay takes to operate, rather than running the numerous-amps clutch current back and forth through the firewall and no-longer-available switches. This is really easy, just get a good quality, name-brand 4-pin relay rated for at least 20A. Terminals are 30, 85, 86, 87.

30: 14ga, via 20A fuse to +12V, preferably ignition-switched
85: 16ga, to ground
86: gets existing wire that presently runs to compressor clutch
87: 14ga new wire to compressor clutch

In the future, I'd like to add an electric radiator fan, because even my 7-blade fan with no clutch can't keep up in traffic

This is why A/C cars got upgraded radiators and, most crucially, fan shrouds. Before you put yourself to the hassle of an electric fan, read through all five chapters of this.

My alternator has a 1963 date stamped on it

Whatever you wind up deciding to do, keep hold of that alternator! Originals like that are very scarce any more. Don't let anybody sandblast the houisings, if they haven't already been.

I'd like to upgrade my alternator. It doesn't need to be crazy - even the 60A units Rockauto specifies for this car would be a major improvement.

Hit the brakes…!

Now, I've read the MAD Electrical article

Forget that halfbrained idiocy from MAD. Read this.

I did the RTE solid-state volt limiter upgrade

Good!

 

[Rubatoguy]

Alternators are rated by their output capacity limit, they don’t push current. Any current flowing out of the alternator is determined by the load drawing the current. No changes to the loading, there won’t be additional current flowing. If you place your high current fans taking power off the alternator stud and the alternator can cover that load and the stock loads, there will be no impact to the stock system while the engine is running. As mentioned, engine off, the battery becomes the power source these added loads will pull its current across the stock wiring, to be avoided. The regulator simply throttles the alternator to cover whatever the demand is, no more, to the limit of what it can be produce. The biggest advantage to running bigger alternators with somewhat stock loads is more available current at idle over stock sized alternators.



The stock fuse box is correctly loaded, anything added to the stock fuse box will not impact the system unless it draws significant current. Doesn’t sound like there is anything to be concerned with on that.

Thank you for explaining this. I was worried that if you upgraded your alternator to say 120 amps, that in itself might cause problems. I now understand it is only a problem if you put additional loads through the stock wiring. (Not if you wired additional loads directly to the alternator.) Do the later models with an external shunt ammeter have the same issue with wiring additional loads though the stock wiring (aside from potentially pegging the ammeter?)

 

[72RoadRunnerGTX]

Forget that halfbrained idiocy from MAD. Read this.

you can do it quickly and cheaply by running two 10ga wires with ring terminals at each end directly from the alternator's output terminal to the battery + terminal. Each of these 10ga wires must have two 50A fuses, one located within inches of the alternator output terminal and the other located within inches of the battery + terminal.

Put the wires in sleeve/loom and route them where they're not likely to be snagged or cut. Across the top of the radiator support panel with anchored zip ties works well, or tucked under the lip at the top of the rad support. Once you've installed these wires your ammeter will no longer read correctly but you won't be running high current back and forth via thin wires through the firewall and low-rated ammeter, which is where the melt/burn/fire danger comes from.

That approach is the so called "shunt wire bypass", what do you think will happen should a short take place anywhere in the stock 12ga charge path/load distribution wiring or your "thin wires through the firewall and low rated ammeter" with this by-pass in place? Very dangerous, three-way paralleled circuit protection devices, stock fusible link and two legs running 50 amp fuses each? Not a big fan of the Mad approach myself but it’s far safer than any variation of this “shunt wire”, direct battery to alternator, parallel bypass. Circumvents all circuit protection for the stock wiring in the event of a short circuit.

 

[UGW]

@slantsixdan thanks for all the input, I'll respond in order:

AC is a Mopar system, likely installed by the dealer when the car was almost new. To my knowledge, it is wired as it should be. In any case, I almost never use the AC. I like the idea of relays in general, though.

I think the AC is the reason I have the 7-blade fan. The radiator also had 3 visible rows when I looked inside. It has visible Mopar stampings on the tank, so it's at least a factory peice. Unsure if it's original, but I don't have reason to doubt it. It does not have a shroud. I've seen pictures of the Imperial shroud, on factory AC models, but I haven't found one for sale. I was working on fitting a universal, aluminum, "cut-to-fit" shroud, but it's been a PITA. I haven't given up, but I'm trying to construct it such that it can be installed or removed without pulling the radiator or removing the fan.

Thanks for the Allpar article. It was very informative, but it mostly confirmed what I've already suspected.

I actually added two 10" SPAL pusher fans this week. They're manually activated by a switch under the dash, via relays. The relays get thier main power feed directly from the alternator stud, as @72RoadRunnerGTX suggested, so that there's no draw through the dash harness when the engine is running. Even on battery, they only pull 8A each, so the stock wiring could handle it if I left them on. I added these as an "emergency" measure after I nearly overheated waiting in line to get into a show on a 90 degree morning. I don't use them all the time, but if I'm stuck in city traffic on a hot day, I can activate one or both of them to supplement the mechanical fan. I can also remove the entire setup without a trace - no original wiring was modified!

For what it's worth, I did the old "piece of paper" test with my seven blade fan. It will hold a sheet of paper to the other side of the radiator, so it's pulling air through even without the shroud.

I ordered a Powermaster 95A, round-back, made-in-USA alternator this weekend. I do a lot of in-town driving, and the stock alternator just doesn't keep up at low speeds. Don't worry, though - I never throw away original parts! Given what I've read about the current state of aftermarket quality, I actually plan to keep the original in the trunk as a backup. (The nice thing about an Imperial is there's plenty of room in the trunk!)

Based on what has been said above, I think I should be fine, since I'm not pulling any new load through the stock harness.

My current plan is to leave the stock harness alone. After all, it's been fine for the last 60 years. What I might do, based on my diagram from earlier, is add a 40A fuse at either end of the stock harness so that it can't be overloaded, and create a separate wiring system directly off the alternator for any new upgrades. This seems similar to what @72RoadRunnerGTX has in his "part 6" video.

 

[slantsixdan]

I ordered a Powermaster 95A, round-back, made-in-USA alternator this weekend. Based on what has been said above, I think I should be fine, since I'm not pulling any new load through the stock harness. My current plan is to leave the stock harness alone. After all, it's been fine for the last 60 years.

This is a super-bad idea. There is just no way of wishing around it; your present plan is a keen recipe for extensive electrical system damage. I think your relative lack of understanding of the subject is making you much more confident in this decision than you should be.

Here's another bit of information for you to chew on: Chrysler put considerably stouter charging system wiring in cars built 60-amp rather than 40-amp alternators. Chrysler also never met a penny they didn't pinch til it screamed for mercy. The math does itself on this one.

 

[slantsixdan]

That approach is the so called "shunt wire bypass", what do you think will happen should a short take place anywhere in the stock 12ga charge path/load distribution wiring or your "thin wires through the firewall and low rated ammeter" with this by-pass in place?

That depends if you were or weren't smart enough to take that circuit out of operation.

 

[slantsixdan]

I was worried that if you upgraded your alternator to say 120 amps, that in itself might cause problems. I now understand it is only a problem if you put additional loads through the stock wiring.

…which is fine if you can guarantee that the only loads on the system will be the ones you plan and deliberately induce. But you can't, because stuff happens. Let a cell quietly die in your battery one fine day, and now your alternator will be putting out as much current as it can, even though you didn't plan for it to do so.

 

[72RoadRunnerGTX]

That depends if you were or weren't smart enough to take that circuit out of operation.

Funny, you don’t mention anything about that in the promotion of your direct battery to alternator dual bypass, in fact, you say “the ammeter will no longer read correctly” that would indicate you are suggesting to overlay/parallel the existing charge path/wiring. So, doesn’t taking the original charge path “out of operation” just make it the MAD approach?
I think I’m smart enough to recognize the danger of the bypass when performed just the way you described it, would never do that. What I don’t get, stock wiring aside, is the logic behind the dual/parallel 10 gauge wires and the 4 fuses? Numbers don’t make sense, with 10ga wire with rated ampacity at about 30-40amps and a total circuit protection level for both parallel 50 amp fuses at 100 amps according to Kirchhoff’s current dividing rule, how will that protect any segment of the 10ga wires in the event of a short? What’s the logic behind the fuses at each end of each leg when the battery is the only power source with the current potential needed to smoke your 10ga wiring?

 

[UGW]

This is a super-bad idea. There is just no way of wishing around it; your present plan is a keen recipe for extensive electrical system damage. I think your relative lack of understanding of the subject is making you much more confident in this decision than you should be.

Here's another bit of information for you to chew on: Chrysler put considerably stouter charging system wiring in cars built 60-amp rather than 40-amp alternators. Chrysler also never met a penny they didn't pinch til it screamed for mercy. The math does itself on this one.

I'm fully willing to accept that I don't know what I'm doing. That's why I posted in the first place, and I'm not doing anything until I'm certain of the plan. So, it's a terrible idea that will definitely destroy my electrical system. Can you help me understand why, in technical terms? I initially thought the "shunt" was a good idea, but then I watched some of @72RoadRunnerGTX 's videos and read up on Kirchoff's rule. (I'm not a professional electrical engineer, but I do have some adjacent experience, and I'm pretty good with math and diagrams.)

My current plan would be something like:

[battery] -> [starter relay] -> [40A fuse] - red wire to bulkhead -> || "stuff inside car" || - black wire from bulkhead -> [40A fuse] -> #4 wire -> (alternator) -> #4 wire -> [aux fuse block, accessories]

I'm open to the idea I might be missing something, but it seems like in this design, the 40A fuses mean the stock wiring never sees more than the max stock current, even if all the new accessories try to draw from the battery, or the alternator starts cranking full blast. (The dead battery cell was a good call, BTW. I hadn't thought of that.) If anything goes awry in either direction, the fuse should blow first. Inconvenient, for sure, but way better than an electrical fire?

(Sorry if I've started a holy war. I just try to do things the right way, or not at all.)

 

[72RoadRunnerGTX]

I'm open to the idea I might be missing something, but it seems like in this design, the 40A fuses mean the stock wiring never sees more than the max stock current, even if all the new accessories try to draw from the battery, or the alternator starts cranking full blast. (The dead battery cell was a good call, BTW. I hadn't thought of that.) If anything goes awry in either direction, the fuse should blow first. Inconvenient, for sure, but way better than an electrical fire?

Monitoring the health of the battery is the primary purpose of the ammeter as originally designed. A centered ammeter while running indicates a healthy charging system/battery status. High or abnormal charge rates would indicate an internal battery issue and an imminent battery failure is likely or misplaced added running loads connected at the battery. Left as stock, stock alternator size, the stock fusible link will protect the stock wiring from any alternator sourced over-current as well as battery sourced over-current. The proposed 40-amp fuse isolating the stock wiring/loads from the proposed upgraded alternator should protect the stock wiring from any added alternator current potential. That said, short of the this kind of added fuse protection, it is a good idea to do the fleet bypass, upsize the charge path wiring, bypass the bulkhead Packard connections when upgrading the alternator output.

 

[UGW]

OK, here's my current plan, with the goal of keeping everything 100% reversible:

- The factory circuit has a 40A fuse on both ends, preventing over-current from entering the original harness
- I'm using marine battery terminal mount fuses, which have the advantage of no added wiring, and bolting right over the alternator and starter relay lugs. (picture below) They also have some pretty heavy-duty capacity.

Now, with the 95A alternator installed, I've got two problems:

- I'm still not getting enough charge current at idle
- The alternator sounds like it's working really hard at curb idle

I called Powermaster's tech line (major credit to them for USA-based product and support!) and the specialist I spoke to suggested my problem is that I didn't upgrade the charge circuit wiring. The alternator just can't push current to charge the battery along with everything else through the 12ga wire.

So, I'm proposing adding a #4 charge wire direct from the alternator to the starter relay, per Powermaster's recommendation. I've also ordered a solid state voltage regulator, as the packaging also suggested that would work best with the new alternator.

I'm hoping people here can check my work. This looks suspiciously like the "shunt wire" that @72RoadRunnerGTX debunked with his videos, which I've watched. (Thank you, those were so informative!) However, my understanding with the shunt wire bypass is that the problem is that the fusible link is only at the starter relay, on the "left" side of the circuit, and the shunt allows overloading the "right" side of the circuit without activating the bypass. In this design, both ends of the stock circuit are fused, so that shouldn't be possible? I guess if something shorted, it could pull 40A from each leg, culminating at 80A at the termination - but that should blow a smaller fuse in the interior fuse block first.

I think this might invalidate the ammeter, but I have a modern voltmeter as well so that doesn't concern me.

In this design, the only place high current can travel is between the battery and the alternator (and the starter, but that's irrelevant) right? If this doesn't work, I guess my only options are a full custom harness, or back to the 39A alternator.

Photos of terminal fuses installed, for reference:

I used a double terminal on the alternator for future expansion. Only one is currently used.