I have a 1984 4 cyl manual Fiero with AC. No power locks or windows. Power mirror adjust. (Got rid of rusted 1987 Fiero. )

I had a dead battery and failure to even click the solenoid when the battery had been recharged.

Using advice from this forum (as I recall) I used the 10A shunt on my cheap multimeter with the car off, no keys in ignition. It was reading over 8 A. I removed fuses one by one to locate the problem circuit. When I pulled the BATT WDO fuse the draw dropped to around 1.2 A, still too high. When I also pulled the STOP HAZ fuse the draw dropped to zero. When I put the BATT WDO fuse (only) back in the draw was 7.2 A. This seemed odd so I reproduced it.

I left both BATT WDO and STOP HAZ fuses out and the car started. headlights went up and on but will not go down. No interior lights. Emergency flashers work. No radio. Not sure about brake lights.

I recently had overheating issues which I partially resolved by running the AC to force the radiator fan on. After this electrical issue happened I also burped the radiator, which had been a problem I realized. This issue may have started right after the car was getting too hot or not. Not sure. I don't think these are related unless the heat fried some wires.

HELP! (please)

You should have a drain of about 18mA, due to the ECM. You definitely have full a short. You'll need to trace both circuits.

(sorry...not the reply you were hoping for, I'm sure...)

[This message has been edited by Neils88 (edited 07-16-2015).]

Any replies appreciated. I read some more are saw that the BATT WDO is actually just BATT with the WDO pointing up and to the right. That this involves two different circuits is interesting. There was a circuit diagram I could not understand which linked a dimmer to many circuits.

I just ran the car and put each fuse back temporarily. I figured that a full short might stop something from working, if it was at ground instead of 12 VDC. The interior lights seemed to work again with the STOP HAZ fuse in. With the BATT fuse in the passenger side front side and rear side running lights did not light. The passenger side front side turn signal did not work either, likely the same bulb. I mean the lights on the side of the car. The driver side side lights worked fine with the BATT fuse back in.


I guess the next step is to check the bulbs.

Then figure out how the wires run from the console controls to the side signals? I hope there are wire harness diagrams somewhere.

Are these side lights turned on by grounding them or supplying them power as they are already grounded?

Oh yeah, this is off topic but I have been doing house wiring lately on my house. The Wago 222 lever nuts are awesome. They would work on cars as well. I may need to use them here. They are good for repeatedly connecting, disconnecting, and reconnecting wires as you make mistakes and change your plans etc. More expensive than wire nuts but you don't mangle the wires each time. The upcoming 221 wire nuts could be even better, slimmer, and able to handle a little more current than 20 A.

Is your radio original? I would pull it and see if there was a mess left under there from a previous owner.

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What part of your car is getting as hot as a 100W light bulb?

12v x 8a = 96W

quote Originally posted by phonedawgz: What part of your car is getting as hot as a 100W light bulb? 12v x 8a = 96W

Interesting idea. I am not sure where to start looking. maybe at night after the sun goes down and the engine is cool I could search. Maybe I could use the HFT IR temp reader (the red dot reader)? That is how I traced heating pipes in walls in my old house.

My alternator belt broke so I need to replace that. I am not sure when that happened. That explains why the car killed in traffic, not why there is the 8A drain when off.

Q. I can trace the pos cable from battery to alternator then it goes somewhere. Is there any easy way (diagrams) to trace the wires? I have no idea where they go.

Q. Where is this 'C500' thing located. Sorry for being clueless.

As I understand the car chassis circuit here is how it works: (please correct me if I am wrong). Until recently I did not know that most devices are always powered and grounded to turn them on. I thought it was like a house.

The battery pos cable goes through some fusible link (perhaps) then supplies the fuse panel. The individual fuses have a singe wire run to each of the devices e.g. a side running light. The side running light is always powered but only lights when it is grounded. There are multiple ways to ground the light as it may be used along with the headlights at night and as a turn signal all the time.

If the short to ground was after the device I would expect the device to always be on, but that is not the case (e.g. lights).

So, I am looking for direct short between a wire coming from the fuse in question (actually two different fuses) and connecting to the device e.g. the side running light. If I put that fuse back in (for a little while for testing) I expect to find 0 VDC along the whole wire because it is grounded?

I would expect the device in question on the shorted wire to not work because the 12 VDC is going to ground, not the device, correct? All my lights work. Maybe pull the console apart to see the cigarette lighter wiring.

I see that the headlight motors raise the lights even with the BATT and the HAZ fuses pulled. The motors only lower the lights when the BATT fuse is in. If it is the motors how to troubleshoot?

BTW, I found and used this device from Harbor Freight. Instead of running back and forth to measure the draw on the battery after pulling a fuse I just measure the draw directly at the fuse panel. 30 Amp Automotive Fuse Circuit Tester $13.99

I really appreciate any help.

A bad alternator can be a huge drain. I had a good fully charged battery after a short road trip and parked the car. An hour later, it wouldnt light a dome lite. Battery charged fine disconnected. Changed the alternator and everything was normal again.

Partial isolation. I pulled the headlight isolation relay and the 7.2 A draw on the BATT circuit dropped to zero. So it has something to do with the headlight motors or the relays themselves.

The 1.2A draw on the STOP HAZ fuse remains.