Ammeter bypass
- Thread starter bronze turbine
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I like the diagrams you whipped up, also a great refresher on electrical basics. Completely forgot about Ohm's law and parallel circuits. This one in particular shows how the bulkhead connector bypass should be done, as well as where to place additional loads within the circuit.
The only issue I can see is if the engine is off and you for whatever reason, need to have the headlights on. Or maybe you're just listening to music at a moderately loud volume. Would the ammeter have problems with that?
The only issue I can see is if the engine is off and you for whatever reason, need to have the headlights on. Or maybe you're just listening to music at a moderately loud volume. Would the ammeter have problems with that?
72RoadRunnerGTX
New Member
That is correct, the only circumstance where the ammeter is exposed to full vehicle loads is when the engine is off, or engine is running, and the charging system is inoperative for whatever reason. These passenger car ammeters from this time are robustly constructed and can handle quite a bit of current assuming the connections/insulators at the ammeter are in good shape and have not been abused/neglected previously. Most are scaled at about 40 amps one way or the other. The internal bus dimensions enable a much higher tolerance. The stud head to bus connection would be the limiting factor. Verry important to maintain tight ammeter stud nuts but not so tight that the fiberboard insulators are crushed/damaged.
In one of the videos linked, it shows one of my cars running 400 watts if Hella lighting with engine off. Drawing about 25amps, have no concerns with this current through the upsized wiring and ammeter at all. Would have more concern with how long I could run those lights before I couldn’t get the car started.
There was a time when I spent a great deal of time sitting listening to the radio/sound system with the engine off, don’t do much of that these days. There was another time when I ran around with a trunk full of audio amplifiers and/or designed such systems professionally. Would design a separate isolated battery system to power these systems and have no impact to the stock charging/starting system.
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That sounds interesting (to me at least LOL) and I'd like to see an example of how you did the isolated battery system.
72RoadRunnerGTX
New Member
Basically. the same as the “House” or auxiliary 12-volt systems in R/Vs or marine applications. A separate electrical system based around a trunk mounted battery (typically deep cycle), having all audio components connected separately and isolated completely from the car’s electrical system. Using a battery isolator installed at the alternator output to charge both systems as needed but prevent any current draw from either system to/from the other. Effectively isolates the stock/starting system from any impact from the sound system and its battery state. I'll work on a diagram when I get a minute.
Might be similar to some light-duty truck applications where there is an extra battery for the attached travel trailer to run off of? Factory "isolation" battery and harness, charged by the vehicles charging system. I know GM had such an option a while back. Might be more common in the travel trailer world?
CBODY67
Finally got around to doing the bulkhead bypass I mentioned I was gonna do earlier. Used a step drill bit and drilled two 8mm holes just under the bulkhead connector, spot painted it with some black spray paint to prevent rust, before sticking a grommet in each hole. Kinda shitty pic; took it at night and it was raining lol. You can see the red and black 10 gauge wires I added in the bottom left corner of the pic. Red goes to alternator, black to battery. I should've swapped the cable colours around...oh well.
Removed and taped off the stock eye terminal on the back of the alternator, then taped off the eye terminal of the battery wire going to the red stud on the ammeter. As mentioned, unfortunately, I forgot about the whole red stud on the back of the ammeter thing, so now the black wire has to go to the red stud and vice versa lol. But it all works. Screwed down the factory black wire on the black stud, together with the new wires, so now the factory power feed pins on the bulkhead are completely bypasssed while the ammeter still works as intended.
Waiting for paint to dry is annoying...I think I'm going to buy a bottle of nail polish top coat. Stuff is great for protecting interior plastic buttons from rubbing off, might serve me well in coating exposed steel.
Update: re-reading the MAD article again...as far as I can tell, it matches what 72RoadRunner is saying - to bypass the bulkhead connector packard terminals, it even says those are the weakest link in the whole system. It mentions the primary reason for bypassing the ammeter is because the gauge "often fails" and "sometimes it burns dashes." So it's basically just trying to eliminate a potential fire hazard inside the cabin. A point of contention could be made if the passenger car ammeter internals are beefier than people realise however, in which case, the stock ammeter can be included in the new circuit, and when used in conjunction with one of those little cigarette lighter voltmeters, can give you more information about the electrical system. The article makes no mention about proper load placement however, which is probably where people start having problems.
So basically...
- bulkhead connector sucks, bypass the power feed terminals on that with 12 gauge wire at an absolute minimum, larger if futureproofing/adding more electrical stuff
- passenger car mopar ammeters are beefier than people give them credit for
- additional loads should be placed on the wire between the alternator and ammeter stud, preferably as close to the alternator as possible
Removed and taped off the stock eye terminal on the back of the alternator, then taped off the eye terminal of the battery wire going to the red stud on the ammeter. As mentioned, unfortunately, I forgot about the whole red stud on the back of the ammeter thing, so now the black wire has to go to the red stud and vice versa lol. But it all works. Screwed down the factory black wire on the black stud, together with the new wires, so now the factory power feed pins on the bulkhead are completely bypasssed while the ammeter still works as intended.
Waiting for paint to dry is annoying...I think I'm going to buy a bottle of nail polish top coat. Stuff is great for protecting interior plastic buttons from rubbing off, might serve me well in coating exposed steel.
Update: re-reading the MAD article again...as far as I can tell, it matches what 72RoadRunner is saying - to bypass the bulkhead connector packard terminals, it even says those are the weakest link in the whole system. It mentions the primary reason for bypassing the ammeter is because the gauge "often fails" and "sometimes it burns dashes." So it's basically just trying to eliminate a potential fire hazard inside the cabin. A point of contention could be made if the passenger car ammeter internals are beefier than people realise however, in which case, the stock ammeter can be included in the new circuit, and when used in conjunction with one of those little cigarette lighter voltmeters, can give you more information about the electrical system. The article makes no mention about proper load placement however, which is probably where people start having problems.
So basically...
- bulkhead connector sucks, bypass the power feed terminals on that with 12 gauge wire at an absolute minimum, larger if futureproofing/adding more electrical stuff
- passenger car mopar ammeters are beefier than people give them credit for
- additional loads should be placed on the wire between the alternator and ammeter stud, preferably as close to the alternator as possible
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72RoadRunnerGTX
New Member
In reference to the MAD Electrical article and its content relating to “Dodge” truck ammeters. The truck ammeters from that time (mid-seventies and up) had a plastic frame and was mounted to a plastic dashboard inner structure. The truck in question is a 1979 and as pictured in the article, these truck ammeters literally melted and deformed with any prolonged exposure to current related heat at the terminals. They were not constructed the same the passenger car ammeters from previous years. I saw a lot of later truck ammeter issues at the dealers back then. Most with A/C and having misplaced added aftermarket loads connected at the battery, wenches, aux lights, radios. Can’t agree with the blanket application of this article to every Chrysler ammeter-based charging system as it relates to ammeter terminal failures. The passenger car ammeters can handle a great deal of current with tight well-maintained connections/insulators.
Another point of contention is the comparison of this system to a generator-based Ford Model A charging system, no comparison.
darth_linux
Well-Known Member
After carefully reading and reflecting upon @72RoadRunnerGTX and others input, my plan for next summer is to relocate the wiring and relays for my headlights over to the alternator side, since they currently sit on the battery side. I haven't had any problems yet, but I do understand that things can and do go wrong, and I'd like to be on the correct side of Ohm's Law
Right. Maybe I'm dumb because I seem to keep forgetting the original context was the Dodge truck ammeters burning and not the car ammeters. In any case, your recommendations are great for cutting through all the misconceptions built up over the decades and I think the three points I summarised should serve anyone looking to update their electrical system on old mopars well.
72RoadRunnerGTX
New Member
To follow up on this subject a bit, as a result of a more recent promotion of this by-pass as making the original system “safe”, without any mention of the added risk by a self-proclaimed Mopar expert YouTuber. I have posted some demonstration videos about this “shunt wire” by-pass and some other related Chrysler electrical issues. Includes my experience with and a demonstration of the above-mentioned C-body charge path recall some here with a pre-externally shunted ammeter may be interested in.
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Hi,I hate to ask but hours of searching and haven't read about this issue.
I did the under the hood ammeter bypass.10g with 14 g jumper wire.
Hooked the battery back up,started it,and then the ammeter maxed out.shut off car,disconnected battery,still pegged full.
Installed a volt meter,12.5 off 14.5 on.
My question is is it safe that the gauge is now maxed out forever? Is this common?
I was hoping for the results I read about,where it goes to the middle of the ammeter.
And tips info would be great thanks.
Car is I think 60s Chrysler new yorker
I did the under the hood ammeter bypass.10g with 14 g jumper wire.
Hooked the battery back up,started it,and then the ammeter maxed out.shut off car,disconnected battery,still pegged full.
Installed a volt meter,12.5 off 14.5 on.
My question is is it safe that the gauge is now maxed out forever? Is this common?
I was hoping for the results I read about,where it goes to the middle of the ammeter.
And tips info would be great thanks.
Car is I think 60s Chrysler new yorker
Hello and welcome to FCBO.
When you say that you've searched for hours about this issue - are you refering to the issue of people altering their wiring because of the belief that the ammeter is a potential problem, or the issue that the legitimacy of this wiring modification is being called into question?
Your photo shows a 1960 to 1962 Chrysler Astrodome instrument cluster. Are you unsure of the exact year or even model of Chrysler car that you own?
Regarding why your ammeter needle is pegged, I don't know if anyone has analyzed a wiring diagram from that era of Chrysler vehicles to know how to impliment the so-called ammeter-bypass mod and how the system would react to the under-hood mod.
The guy is most likely a spammer. Don't engage.
3175375
Senior Member
Excellent videos! Absolutely great explanation and clear descriptions!
Mopar man,,,,, hello and thank you
I did this for the reason the guys previous car burnt down from the ammeter so he wanted to fix this car before it burnt too.
Year of vehicle I'm not exact but it's ok it's not my vehicle and most info said it's for 60s 70s I thought
You are saying the Ammeter bypass is different on this type of vehicle? I'm confused it's the same setup I thought as others....
Big John are you referring to me?
Don't get a job as a spamer finder
Did not post a link or ask for your bank account #
Nothing about that post even comes off as spam but thanks for the warm welcome
I did this for the reason the guys previous car burnt down from the ammeter so he wanted to fix this car before it burnt too.
Year of vehicle I'm not exact but it's ok it's not my vehicle and most info said it's for 60s 70s I thought
You are saying the Ammeter bypass is different on this type of vehicle? I'm confused it's the same setup I thought as others....
Big John are you referring to me?
Don't get a job as a spamer finder
Did not post a link or ask for your bank account #
Nothing about that post even comes off as spam but thanks for the warm welcome
3175375
Senior Member
Bypassing the ammeter only doesn’t do much.
The wiring through the bulkhead and the continuous current running through the fuse block is basically the issue. Keeping high current loads out of the cabin and out of the connector block is the real key to improving the electrical safety of our vehicles.
Hello @flchrny
I strongly recommend that you and / or the actual owner of that Chrysler watch several of the youtube video's made by @72RoadRunnerGTX regarding the ammeter bypass. He explains why the bypass has practically no value and introduces new vulnerabilities to the electrical system, and he explains the likely reasons why this bypass originated (ie when and for what vehicles, which are not our cars).
I would say that anyone with a seldom or infrequently-driven old car should simply disconnect the battery (remove positive battery cable) when the car is parked. It's simple to do, and removes any chance that a wiring fault in the car would start a fire when the car is parked / unattended.
Can you describe what happened to the previous car that burned down? What was the make/model/year of the car, and the fault that caused the fire?
On this vehicle I did not see a bulkhead block on the firewall,I did however see a similar looking plug under the dash inside and it looked fine.
This guy did not want to take his dash apart therefore the time I spent researching sounded like doing the under the hood bypass would hurt nothing and take stress off the ammeter.
Moparman thank you for the replies.
I am trying to find out year of the current now and I will ask year of the car that burnt.he said it was a new yorker also I know that.
What he said happened was ,he was driving and the ammeter jumped from full then down then full and stuck "while driving" and once it stuck full he said smoke came from the dash and started on fire he said the fire department showed up and filled the car with foam and further ruined the car.
All the reading I did said that simple alt to starter solenoid bypass was harmless,now you say it's actually bad? I'm so confused right now.
This guy did not want to take his dash apart therefore the time I spent researching sounded like doing the under the hood bypass would hurt nothing and take stress off the ammeter.
Moparman thank you for the replies.
I am trying to find out year of the current now and I will ask year of the car that burnt.he said it was a new yorker also I know that.
What he said happened was ,he was driving and the ammeter jumped from full then down then full and stuck "while driving" and once it stuck full he said smoke came from the dash and started on fire he said the fire department showed up and filled the car with foam and further ruined the car.
All the reading I did said that simple alt to starter solenoid bypass was harmless,now you say it's actually bad? I'm so confused right now.
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