Ammeter bypass
- Thread starter bronze turbine
- Start date
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.
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