Wire connecting alt posts?

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Crusty Brian

Crusty Brian

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I'm installing a new dash wire harness in my 67 Dart GT, aside from needing to solder some pins back into the circuit board, the board looks to be in great shape. Except it has a wire connecting the + and - posts on the alternator gauge(on top of the standard red and black wires). This is my 5th Dart and I've never ran into this before. Any ideas? (I'm also aware that this is probably a simple *** question) By the way the gauge was the only one that worked and was surprisingly accurate
 
It should not be marked (-) but I sure haven't seen them all. The important point is that both posts are 'hot' at all times. It must never be grounded. Some have the battery post marked 'R' or red because the battery feed is red insulated. The other post connects to the main splice (standard) or in very rare cases feeds back out through a grommet in the firewall to a terminal junction with the alternator and the bulkhead multi-connector.

That it works is not surprising because its not like the other gages:
The ammeter is directly in the battery output/charge line. Inside is a big metal plate and the needle is moved by small magnetic field created when current flows through it. (Except for 1976 models which have a remote shunt)
The other gages are thermo-electric. Those needles move as current flowing through creates heat that changes the bend on the hairpin shape. They need to be supplied through the instrument voltage limiter.

if you want help with the pin repairs, do a search and you should be able to find those posts pretty easily
 
your going to need to trace them out. i'm not aware of any extra factory wiring coming off the ammeter
 
The gauge needle responds to current passing through the shunt. So a jumper wire across, outside the gauge, should have lessened gauge accuracy.
 
Crusty Brian said:
I'm installing a new dash wire harness in my 67 Dart GT, aside from needing to solder some pins back into the circuit board, the board looks to be in great shape. Except it has a wire connecting the + and - posts on the alternator gauge(on top of the standard red and black wires). This is my 5th Dart and I've never ran into this before. Any ideas? (I'm also aware that this is probably a simple *** question) By the way the gauge was the only one that worked and was surprisingly accurate
Click to expand...

How large is the wire and photo if possible.
 
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67Dart273 said:
How large is the wire and photo if possible.
Click to expand...
 
My bad earlier saying it was + and -, I just skipped saying red and black wire. The gauge works great I was just curious if anyone had seen this before, granted I'm not done rooting through the **** show of rewiring (all blue and looks to be 18 gauge except for the tan home stereo speaker wires used(!). I appreciate all the input and I'm sorry about my internet skills
 
That looks a LOT bigger than 18 gau and what do you mean "gauge works great?" I don't know how it possibly CAN. You just turned (wild guess) a 50A ammeter into about a 100A or 150A ammeter

What they have done there is added a shunt in parallel. Shuts are easier to understand except in the case of most old school auto ammeters. This is because the shunt (in the meter) is PART OF the meter movement. Someone paralleled the factory "shunt" with that wire, which makes the ammeter move less with a given current flow.
 
I meant 18 gauge under the dash, the jumper wire is 12 gauge. And when I was having issues with the voltage regulator (was just not getting a good ground) I check it constantly with a multi meter multiple times and was getting 14 volts on the battery and the gauge would read just a hair to the right of the center line
 
What you want to do is see what it does under less load. Say, turn on the headlights, see if/ how far it moves, with engine stopped. Turn on the key, turn on heater blower, step on brakes. "I bet" you can't even see the needle move.
 
67Dart273 said:
What you want to do is see what it does under less load. Say, turn on the headlights, see if/ how far it moves, with engine stopped. Turn on the key, turn on heater blower, step on brakes. "I bet" you can't even see the needle move.
Click to expand...
I did that and it acted like it should! Even dumps down a bit when cranking the engine. I hear what your saying and I'm surprised as well! But like I said I'm not done tearing the rats nest out from under the dash. Its a total **** show, bunch of after market gauges and lights
 
If its really accurate, which I agree the the others that seems dubious, the only possibilty I can think of is that someone changed the original ammeter for a shunted one.
Factory they were available only a few years and models for example 1976 A-body.
Aftermarket they have always been available. Prices are not cheap.

But if the wires leading to it are 18 gage, there will be a huge problem. Hopefully I misunderstood that.

To check the what the regulator is doing, measure how much voltage difference exists between the regulator input, the battery, and the alternator output.
This has to be done with some load, preferably a consistant load like the parking lights.
 
UPDATE: Once I got the harness almost out I found the there was a wire spliced into the ignition switch connection (I'll post a picture) the wire ran thru the firewall to the ignition connection on the voltage regulator, with a smaller wire also connected to the ignition connection, but ran to the ballast resistor. I have no clue if that would make sense with the fuckery on the alt gauge
 
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