Parasitic battery drain - what am I missing? (Page 1/5)
CenLA JUN 15, 10:21 PM
I know electrical shorts are a pain, but I'm missing something and need a hero.

86 Fiero SE V6 battery went completely dead. Without thinking I bought a new one and got my son out of the bad neighborhood it broke down in.

But the next day the new battery was dead. So I fully charged it and went for a spin. While driving it never really went above 13 volts on the dash gauge and less when I turned anything on. When idling, I checked the voltage across the battery terminals and once it spiked over 14v but mostly stayed between 12 and 13.5v.
I also checked the negative cable contact where it bolts to the engine and the smaller wire to the firewall trim but they were secure and clean.

Following the advice from a few different threads on this wonderful resource, I pulled out the multimeter and sure enough there was a 2.86 amp draw instead of less than 50ma. We jammed the door switch, then pulled and reinserted every fuse in the box under the steering wheel but the ammeter stayed between 2.85 and 2.88. I also pulled the single-wire inline fuse at each headlight. I should mention I'm not hearing any clicking at the headlight motors either nor a fuel pump motor.
No change. Is there another fuse box I'm missing somewhere?

Now the only thing I have noticed for sure that was working before this incident but not since is the trunk light. I have checked the orange cable at it had like 12.4v when I put it between the meter and ground. Still, the light wouldn't come on but when I disconnected the trunk light assembly and hooked it up directly to the battery with alligator clips the light came on like it should. Which makes me wonder if the second wire (white) to the trunk light, presumably a ground, is working properly.

I've been looking at the electrical schematics online and cannot find the one that shows the trunk light (do you have one??) on it so I'm not sure where to go from here.

The battery is at 12.55v right now. By morning it will be dead. <big sigh>

Thanks in advance for any help!!

[This message has been edited by CenLA (edited 06-15-2014).]

fierofool JUN 15, 10:59 PM
With the battery at full charge, unplug the harness from the oil pressure sending unit and let it sit overnight. You may not hear the fuel pump running.

[This message has been edited by fierofool (edited 06-15-2014).]

IXSLR8 JUN 15, 11:05 PM
Try unhooking your alternator battery wire. I've had a bad alternator that did this to me.
CenLA JUN 15, 11:07 PM

quote
Originally posted by fierofool:

With the battery at full charge, unplug the harness from the oil pressure sending unit and let it sit overnight. You may not hear the fuel pump running.




I'll do that right now before I crash for the night. What are you thinking?

BTW, in reference to my trunk light which I *think* is on the same circuit as my power windows and trunk release, they still all work.

I'm not getting any ADSL (or whatever it is) codes other than normal Code 12 (one blink of the SES, pause, two blinks, pause, and repeat) if that helps.
fastblack JUN 15, 11:11 PM

quote
Originally posted by IXSLR8:

Try unhooking your alternator battery wire. I've had a bad alternator that did this to me.



Me too.

If it's still there after unhooking the alt, the logical answer is the wire going to your starter. Check out the Ogre's Cave (links at the top and bottom of every page) for great help tracking down electrical gremlins. Trust me, I know how frustrating they can be, had to make my wife push me across a Target parking lot to bump start the car once
theogre JUN 15, 11:13 PM

quote
Originally posted by fastblack:
If it's still there after unhooking the alt, the logical answer is the wire going to your starter. Check out the Ogre's Cave (links at the top and bottom of every page) for great help tracking down electrical gremlins. Trust me, I know how frustrating they can be, had to make my wife push me across a Target parking lot to bump start the car once


Start here
See my Cave, Battery Leaches

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

[This message has been edited by theogre (edited 01-15-2021).]

fierofool JUN 16, 08:33 AM
Referencing the oil pressure sending unit, I had a battery drain on my 86SE. Just happened that one morning the battery was dead. Charged it up and the next morning it was dead. Got a new battery and the next morning, that one was dead. One of our local Fiero mechanics suggested that it was the oil pressure sender. I put a meter on the battery and unplugged the oil pressure sender and the voltage jumped back up.

There's unswitched 12 volts going to the sender. The other two wires feed the oil pressure gauge and fuel pump backup circuit. You may not hear the fuel pump run.
CenLA JUN 16, 09:33 PM
Okay, so here's where I'm at.

I couldn't figure out how to disconnect the oil sender plug. So I left it for now. I was afraid I'd break it like I did previously on the coolant fan switch.

I went to every plug-type connection I could find on the block or in the engine compartment and tested after each. Still 3.18 amps on average.

Then I disconnected the thick red cable on the back of the alternator and tried it again. It dropped to roughly .28 amps. Does this make the alternator the actual problem or is it just the beginning in a series of steps to getting to another problem?

Ogre, I had already found your page on Google and read it, stopping at the point where is says IF PULLING THE FUSES DOESN'T WORK. I dunno why I stopped there (maybe frustration) but after I went back to it, I started with the alternator and stopped when I got this .28 amp reading which I'm thinking is still way higher than 50mA, right?

Any recommendations as to where to go next?
fierofool JUN 16, 10:14 PM
The 86 has a rubber cap that just pushes down onto the 3 prongs on the top of the sender. To unplug it, simply pull straight up. Some of those rubber caps have a plastic retainer around them. Find the juncture of the ring where it lathes and open it up. You should then be able to pull the harness up and off the sender.
kendallville JUN 16, 10:25 PM

quote
Originally posted by fastblack:


Trust me, I know how frustrating they can be, had to make my wife push me across a Target parking lot to bump start the car once



Strong wife, I would not tick her off