Ammeter pegs minus 20

[poos]

When the headlight switch is turned on all the lights come on as they should. The problem is that the ammeter shows - 20 amps even with the car running. When the lights are turned off the meter reads about 3 amps charge. What suggestions are there for tracking down the problem ? Thanks Poos

[Patrick L.]

Unplug one headlight [ twist connector at the light bucket] at a time and watch the ammeter. See which light, if any or both, is/are causing a problem. This is jumping the gun, but, the headlight connectors can be problematic. Thats why i'm thinking the problem could very well be a headlight connector.

Just keep disconnecting things until the problem stops, that your problem.
If the switch is turned to just the park lights, what does the ammeter show ?
When the brake lights are on, what does it show ?




I wouldn't recommend driving it with the lights on until the grounding/short issue is fixed.

[Charlie Stephens]

If your ammeter is pegging at -20 you have a short somewhere that might cause a fire. I think I would start by putting a fuze in the system.

Charlie Stephens

[Charlie Stephens]

Originally Posted by poos

When the headlight switch is turned on all the lights come on as they should. The problem is that the ammeter shows - 20 amps even with the car running. When the lights are turned off the meter reads about 3 amps charge. What suggestions are there for tracking down the problem ? Thanks Poos

When you say all the lights I assume you are including the tail light, if not check it.

Charlie Stephens

[Pinesdune]

After you've checked the lights for shorts like Patrick said, if you still have the issue, it could be that your charging system isn't cutting in under load/can't keep up to the load. Or your ammeter is faulty and goes off the deep end when it goes into a discharge state.


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[Charlie Stephens]

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What type of lights do you have? Stock?

Charlie Stephens

[Bob C]

Is there a chance you have both high and low beams on at the same time??

Bob

[Tomy Turbos]

Originally Posted by Bob C

Is there a chance you have both high and low beams on at the same time??

Bob

Model A's have High Beams? I never noticed...

[Tom Wesenberg]

The brake switch could also have grounded out.
Remove the two wires going to the switch and see if that fixes the short.

[PC/SR]

When I was a teenager a guy wanted me to rewire his PU because of excess discharge with the lights on. He had sealed beams and they take more amperage than the originals. It got dicey trying to adjust the generator to reduce/eliminate the discharge and still not overcharge when the lights were off.

[CWPASADENA]

Besides checking the lights as others have suggested,

It also sounds like you do not have enough generator output.

If it is an original generator, increase the charging rate a bit.

If the generator has a regulator, look into why you only have 3 amp output.

My opinion,

Chris W.

[Chuck Sea/Tac]

I agree with Chris. You're charging system isn't right. Do you have a multimeter to check voltages ect?

[larrys40]

I concur with Chris as well. Check and make sure you are charging 8 amps or so with the generator on fast idle... If not adjust accordingly with the lights off. For more constant night time driving you may want more but I would start with the 8 amps.

Once there turn on the headlights and see what you have. You may have a zero or near zero output then or possibly a slight discharge. The ammeters themselves on the A's whether they are original or aftermarket are not always accurate.. so take them with the grain of salt.

My suggestion to check and see if you have a short in your light harness is touse a volt ohm meter and disconnect the light harness at the cutout, and remove all tail/headlight bulbs. with the low beams on and the leads connected from hot to ground you should NOT have a short. If you do you have a short in the harness. disconnect or test the leads from the bulb contacts to ground to narrow.

Methodical use of the meter will help you locate it and is your best tool.
Larry Shepard

[Patrick L.]

3 amp output is OK as long as you don't run too much with the headlights on. Its easier on the battery.
If the lights are used a lot then increasing the charge rate to 8-10 amps is fine.
JMHO

[Barry B./ Ma.]

Sounds like both hi and low filaments are both on which happened to me a few times before I changed the connectors with the lousy contact ends.

[Patrick L.]

Originally Posted by Barry B./ Ma.

Sounds like both hi and low filaments are both on which happened to me a few times before I changed the connectors with the lousy contact ends.

Those connectors can be a royal PITA. Some fellas play around with them to get them working.
Others just get rid of them and hard wire them. I'm in this camp.