Ammeter bypass

[72RoadRunnerGTX]

The big reason is the old wives tale about the ammeter bursting into flames and kidnapping the Lindberg baby.

I watched this video yesterday (thanks) and it made a lot of sense to me. I've been of the opinion that most cars don't need this, but it's not a bad option. Your video has me rethinking that.

There is so much confusion and misinformation out there about the charging circuits that it's tough for guys to know exactly what to do. I've even seen some really bad, burn your car down type things happening. For example, I've read of guys putting large fuses on small wires... Thus the wire would burn way before the fuses would blow. I tried explaining that one and common sense did not prevail.

One recently was using Home Depot wire to do a "bypass" (at least it was stranded). I quickly realized that trying to explain that automotive wire was built to take the flex and home wiring wasn't would have fallen on deaf ears and 10 guys would have defended using that wire.

Funny, I’ve been battling misinformation/misconceptions about this charging system since my days working at the dealers back then. More recently, on-line on the various Mopar forums for years. Amazes me how the myth of the “spontaneously combusting” Mopar ammeter just continues on and on unabated and people are still just eating it up. The old “If I read it in a magazine/on-line article or post, it must be true” syndrome. Sometimes I’m met with a lot of uneducated push-back.

Several more recent YouTube videos promoting this bypass without mention of the serious added risk are just outright dangerous. One guy shows what appears to be 4/0 ga cable connected at the alternator stud straight to a battery clamp bolt. Freely admits he sourced the “commercial grade” cable for free from his place of employment. Then gets belligerent when questioned about its safety in a comment.

Loading this charging system correctly seems to be another area of misconceptions, folks just can’t separate this system from everything else these days. Clamping everything to the battery then when bulkhead or ammeter connections fail, must be the ammeter that’s the problem.

I too, have had numerous conversations over the years about why solid core, or stranded, house wire should not be used in any moving vehicle.

 

[bronze turbine]

The way I see it, there's nothing inherently wrong with the design from the factory. The only thing I can see being a problem is that since all the power for the whole car goes through that ammeter, it could get hot and start a fire if the connections got loose or dirty. I think it's only a 30A alternator on those cars so not a lot of power goes through it anyway. Now when you add a lot of power consuming upgrades and upgrade to higher output alternator, you're going beyond what the engineers envisioned for that design. Chrysler engineers themselves addressed this over the years because I know by 1976 the ammeter didn't have the total power going through it and it was more of a shunt type thing or actually was a voltmeter labeled as an ammeter. If you did the update the way the factory did it I can only see that being a good thing. But, if you do a hack job there's no doubt you could actually be creating more problems then resolving.

 

[72RoadRunnerGTX]

The only condition where full vehicle loads run through the ammeter is when the engine is not running or running and the alternator has failed. During 99% of the operational run time, there should be little to no current flowing through the ammeter, only battery charging current, ammeter needle centered or close to it. For C-bodies the switch to a shunted ammeter was around ’72-73 as I recall.

 

[MoPar~Man]

Can you (or someone) explain the difference between the 2-field-wire vs the 1-field-wire alternators?

Your diagram shows the second field wire on a blue-wire bus running through bulkhead connector 23 to the ignition switch. I'm not sure what functionality is happening with the ignition switch and the alternator there.

 

[72RoadRunnerGTX]

Can you (or someone) explain the difference between the 2-field-wire vs the 1-field-wire alternators?

Your diagram shows the second field wire on a blue-wire bus running through bulkhead connector 23 to the ignition switch. I'm not sure what functionality is happening with the ignition switch and the alternator there.

In 1970 Chrysler switched to an electronic, or solid state, voltage regulator for this system. Along with this change was the use of a “dual isolated field” alternator. Both field contacts being insolated from the alternator chassis ground. Full ignition 1 line voltage in on one side, with the regulator now regulating field current on the negative side of the field coil contact.

1969 and earlier single field alternators grounded one side field contacts to the case, with the mechanical regulator regulating field current on the positive side through the one insolated field contact.

The diagram references the 1970 and later wiring but is unrelated to the charge output path for the subject of the video. Same basic layout since 1960 through the seventies, or for C-bodies, until the change to shunted ammeters.
The specific bulkhead terminal locations are referencing B & E bodies, may not match some C-body applications, general reference only.

 

[MoPar~Man]

Related video:



See also:

Catalog

(AMP gauges at the dash are troublesome. They should be by-passed, and then install a VOLT gauge.)

 

[72RoadRunnerGTX]

http://[URL][URL][URL][URL]http://www.madelectrical.com/electricaltech/amp-gauges.shtml

[/URL][/URL][/URL][/URL] (AMP gauges at the dash are troublesome. They should be by-passed, and then install a VOLT gauge.)

I couldn’t disagree more with that statement. Really, the Mad Electrical article? Read the preface carefully, it was written to address the later seventies Dodge truck plastic cluster framed ammeter fiasco. The passenger car ammeters/cluster are not constructed the same. This is has been the number one article most cited by the promoters of ammeter misinformation for many years.

 

[MoPar~Man]

Don't agree with that statement at all. Really, the Mad Electrical article? Read the preface carefully, it was written to address the later seventies Dodge truck plastic cluster framed ammeter fiasco. The passenger car ammeters/cluster are not constructed the same. This is the article most cited by the promoters of ammeter misinformation.

If you are refering to the statement that I put in brackets, I just put that there because it's the title of the article. When I posted the link and then saw that it appeared as just the word "Catalog" I went back and added the title of the article.

I agree with your analysis that the ammeter bypass using a heavy gauge wire from the alternator to the battery is not safe, at least not without a fuse or circuit breaker. There are better options vs just a fusable link. A failed alternator seems to be overlooked by many, it is perhaps more common than a failed ammeter.

And yes, the advent of more electrical accessories in the later 70's particularly in the trucks seems to have been the catalyst for the backwards-looking at the older cars and thinking that they too must need the ammeter bypass.

I myself have just replaced all the packard contacts in the bulkhead connectors on my '67 Monaco. I don't have A/C. But I can say that the heavy gage power in and out pins on the connectors were melt-damaged but still present - if barely.

I think better circuit breaker protection (to replace the fusable link) is possible, and could also be added at the B alternator terminal.

Putting the bulkhead power connectors into a good condition, and checking your ammeter posts and connections are clean and tight, is I think also necessary. But not the bypass.

 

[72RoadRunnerGTX]

The bulkhead connector charge circuit Packard terminals are/were by far the weakest link in that original design. They should be bypassed altogether with a direct wire run through the firewall separately, directly through to the ammeter, as was the later “fleet bypass”. There is no need at all for a disconnect at the firewall for that circuit. Followed by close inspection of the ammeter terminals and insulators, correcting as needed.

Details of this recommendation were covered in this video on the consequences misplaced added loading to this system.

 

[MoPar~Man]

If you've looked at or replaced the bulkhead connectors or are otherwise satisfied that they are ok, I would just add parallel lines through the bulkhead to the ammeter instead of cutting the existing wires as you describe at the 13:00 mark in the video.

For a stock, un-altered car, adding a headlight relay circuit under the hood, powered off the alternator output, would give the biggest benefit for taking load off the existing bulkhead connectors. For those that have added an electric radiator fan, taking power from the alternator output instead of the battery is also the way to go.

 

[72RoadRunnerGTX]

Those two Packard terminals at the bulkhead connector have been failing since these cars were new. They served one purpose, to allow for a quicker assembly going down the line at the factory. There is no electrical need for them. They are not rated to handle anywhere near the expected/designed stock loads, let alone any added loading. C-bodies typically run more stock loads (A/C, power windows) than other platforms and the higher rate of melted alternator feed Packards showed it (pre-shunted ammeters). There was a C-body recall (Recall 48549) to specifically address it in the mid-seventies, adding a parallel 12ga wire from the alternator to the fuse box.

The referenced mod in the video you mention is commonly known as the fleet by-pass, also involves upsizing the wiring to handle added loads correctly. Not going to terminate new 8ga wire runs at the bulkhead connector when that is the weakest link in the whole system. I avoid parallel wire runs whenever possible, would rather un-wrap harnesses and replace/repair/upsize conductors as needed then re-wrap.

 

[edbods]

Clamping everything to the battery then when bulkhead or ammeter connections fail

wouldn't running the wire from the alternator to the battery positive, then connecting ancillaries like headlights or similar as well to the battery positive also cut down the load on the stock wiring?

 

[72RoadRunnerGTX]

wouldn't running the wire from the alternator to the battery positive, then connecting ancillaries like headlights or similar as well to the battery positive also cut down the load on the stock wiring?

For this charging system, as it was originally designed and with no modifications, all loading needs to take place on the alternator side of the ammeter as are all original factory loads. Adding lights/fans, connect the relay secondary power source at the alternator, not at the battery. There should be no added loads connected at the battery or starter relay. Adding a lot of loads? there are ways to make this system handle high loads safely without altering the way the system was designed to function.

Yes, because the under-hood shunt wire by-pass discussed here circumvents the ammeter and the original charge path, load placement becomes moot. The risk of an electrical fire in the event of a short increases manyfold however as it also circumvents all factory circuit protection for all the factory un-fused wiring. Even if this shunt wire includes a fusible link, thanks to Ohms law as applied to parallel circuits, the factory wiring is still exposed to much more battery current potential, well beyond what they can handle safely.

There are links to two videos in this thread that goes into much detail about this charging system, may want to be sure to review both.

 

[MoPar~Man]

wouldn't running the wire from the alternator to the battery positive, then connecting ancillaries like headlights or similar as well to the battery positive also cut down the load on the stock wiring?

The alternator is a possible candidate for failure, and any wire that's directly connected from the alternator to the battery is going to carry a lot of current when that failure happens. Making that a heavy wire is only going to make matters worse - for the battery - when that happens.

You should not need a heavy wire from the battery to the alternator. The only purpose of that path is to charge the battery, to replenish the battery's charge after you used it to crank the engine to start it, and to keep a light trickle-charge current flowing to the battery when you're driving. The only heavy wire running from the battery is going to the starter. You / we need to see the battery as not the primary source of electrical power in the car, but instead it's the alternator.

The dashboard amp meter is not the villian here. First and foremost it's the bulkhead connections to the battery and the alternator. Connecting the alternator and battery under the hood directly is the lazy 2-bit way to deal with bulkhead connector problems that you may or may not be having. But getting down under the dashboard and putzing with the bulkhead connector is hard work, so the easy underhood pseudo-remedy lives on.

 

[edbods]

Thanks for the replies guys. I did see those videos and the very helpful diagrams, at the moment everything is stock save for a headlight relay harness so until I can get my hands on some 8 gauge wiring, I'll just move the headlight relay feed wire to the alternator. I've cleaned up the bulkhead connectors to at least ease some stress off the wiring as they don't bear signs of overheating (yet).

EDIT: I've actually got some 10 gauge wire lying around - 72RoadRunnerGTX, your diagrams mention 8 gauge wiring - would 10 gauge suffice for a stock setup? If I ever added more electrical stuff, at most it'd probably just be a radio and that's it.

 

[72RoadRunnerGTX]

EDIT: I've actually got some 10 gauge wire lying around - 72RoadRunnerGTX, your diagrams mention 8 gauge wiring - would 10 gauge suffice for a stock setup? If I ever added more electrical stuff, at most it'd probably just be a radio and that's it.

For the headlight relay power wire to be extended to the alternator? Unless you are running some verry high wattage lamps, should be fine. Be sure what ever fuse protection you are running for the relays is also moved to be close to the alternator termination. The reference to 8ga wiring would be if upsizing the entire charging system.

 

[edbods]

Oh sorry, I was actually asking about the bulkhead bypass wiring just from the alternator to the ammeter. Was wondering with the stock setup, if I can get away with just 10 gauge wiring.
It's a 67 Fury, the lamps are 2x 55/60W and 2x 55W H4 and H1 bulbs respectively. The headlight relay harness I got from Octane Lighting, the fuse is very close to the feed wire's ring terminal.
Somewhat off-topic, the harness is pretty good but gonna be honest, the terminal crimping left a bit to be desired. On quite a few of the terminals, I could see one or a few strands of wire splayed, and not under the crimp. Wanted to recrimp them myself but I really don't want to buy a flag terminal crimper that I'll only end up using probably once in my life.

 

[72RoadRunnerGTX]

As long as you don’t plan to run high loads, the 10ga is better than the stock 12ga for that charging circuit. Just be sure to by-pass the bulkhead terminations if you are going to the trouble off rewiring. I would try to solder any questionable crimps.

 

[edbods]

Yeah, I think nothing in my system will draw much power higher than the headlights. Probably at most, AC (if I'm ever bothered enough to actually install one, that is) and/or a radio and some basic speakers. I don't feel like tearing apart the harness though so I may just tape up the stock terminals on the back of the ammeter and the back of the alternator, and make a note of it somewhere for future reference.

 

[72RoadRunnerGTX]

@CBODY67

In the classic generator or alternator power circuit, all of the output went through the gauge for an accurate indication of how much the generating device was working against the load of the electrical system items. Of course, the voltage regulator is a part of this circuit, too.

That was fine when the outputs of non-police vehicle generating devices was under abt 60 amps. BUT as the vehicles age, the gauges can age, too, which can increase resistance and resistance builds heat. Too much heat can make for other things to happen, too.

In abt 1972, Chrysler changed the charging circuit to run the alt gauge via a shunt, where the gauge would indicate only a little of the total charging activities. Which meant the needle didn't move nearly as much, but it did move. By abt 1976, heated rear windows were popular, which came with factory 100amp alternators to run them.

In abt 1970, GM started to phase-in voltmeters rather than ammeters into their vehicles. Claiming that it gave a better indication of the charging system's health. At the time, I didn't really believe that, as i wanted to see if the system was charging and how much, rather than looking at a voltmeter. But I adapted.

There are several threads on the "ammeter bypass" procedure and the reason for it in these forums. Prevention of instrument panel fires is a major reason for this procedure. Not hard to do.

Take care,
CBODY67

Moving this reply to this most recent "ammeter bypass" thread, didn't want to hijack the other thread with this.

Yikes, where to start with a response for that. I’m afraid you are repeating quite a bit of the old standard Mopar ammeter misinformation/hysteria with that post. First, there is no comparison between an old generator-based charging system and this Chrysler alternator-based charging system, apples and oranges. Load current is not displayed on the ammeter under normal operating conditions, with correctly placed loading, it should only register battery charging/discharging current. 99% of the time there is little to no current flowing through the ammeter with a fully charged battery on a healthy system/correctly loaded as originally designed.

These ammeters don’t age and don’t “spontaneously combust” for no reason whatsoever. Resistance and related heat buildup at terminals are caused by abuse or neglect at the ammeter terminations and/or misplaced loading, subjecting the ammeter and its connections to current levels they were not designed to handle.

If you can interpret it correctly, ammeters provide much more real time diagnostic information about the battery and charging system health/status than a voltmeter, may as well be running a charge/no-charge idiot light.

The change to shunted ammeter in ’72 was C-body only, the other platforms continued on with this design for several more production years. The shunted ammeter still displayed charging/discharging current only, did not register load current while the engine was running.

I’m aware of all the ammeter bypass threads being posted, again a lot of misinformation. Not only on this forum but many other Chrysler related forums and online publications. I’ve been countering this misinformation for many years. And after many years of typing out explanations, decided to create a couple videos.