Battery died overnight (Page 1/2)
cvxjet MAY 03, 03:16 PM
I was testing my arm (recovering from shoulder surgery)....the previous night for "Shiftability"........the next day I was going to try to drive my Fiero....Tried to start it and would not do anything....Checked the battery and had 2.8 volts...But it was starting to recover. I put the charger on it...and now it seems fine.

I know that the computer takes a very small amount of power to hold it's "memory"....But what could drain the battery in one night...? The only thing I did was open and close the driver's door......I have started it twice in the last month to charge the battery and get the fluids flowing....each time for approx' 15 minutes.....The last time was a week before the ......Battery's death........
Patrick MAY 03, 04:07 PM
I don't remember what year your Fiero is (which is why you're supposed to mention these things ), but first generation headlight motors are notorious for draining batteries when the cutoff switch (or whatever it's called) fails.

[This message has been edited by Patrick (edited 05-03-2019).]

JMTUT MAY 03, 04:58 PM
I agree with Patrick. Check if there is a clicking noise from the headlight motors that will indicate a worn assembly. The other thing to check is the isolation relay on the drivers side of the inner fender next to the driver light assembly. Sometimes unplugging and plugging back in will "clean" the contacts enough to make everything work. Same for the relay mounted on the inner side of each headlight assembly.
FX MAY 03, 05:56 PM
The weirdest thing I ever had that drained the battery overnight was a bad oil pressure sender. The fuel pump is wired through it, and didn't shut off when I turned the car off. new sender fixed that. They're right about the gen 1 headlight motors. I had a lot of problems with mine. Next time the battery is fully charged put an amp meter between the + battery cable and battery. If you're showing any amperage draw, start unplugging things to find the problem. I think the computer draws about .4 volts. It shouldn't show any amp draw at all...If determined to be faulty isolation relay, Rodney makes an excellent replacement, about 45 bucks. I have one, all color coded, very easy to install...

[This message has been edited by FX (edited 05-03-2019).]

cvxjet MAY 03, 06:59 PM
A) I do know about checking/listening to the headlight motors......B) I have listened to them, but C) I did not actuate them for the last year or so. I rarely drive it at night and when I do I use my combo Driving/Indicator lights which only need the parking lights on, avoiding actuating the headlight motors.

I have charged up the battery and drove it today (Finally, after a month of recovery for shoulder surgery)...It ran fine and I checked the charging system...everything appears good...I will leave the battery hooked up tonight and see if it goes dead tomorrow morning.

As a side note, I moved the battery up front under the spare, but also have a separate starter solenoid so that the big wire is not energized except when starting(Have another (#8) wire to run the car)...I have the battery ground running thru a safety switch too.
armos MAY 06, 01:25 AM
I guess it's been a couple days, but if this is still an issue -
I agree with using an ammeter to find if there's an excessive draw, and if so, start unplugging fuses and components to narrow down the cause from the top. Don't think too much about what *could* be draining it - there's too many possibilities if you look at it from that direction.

If you don't have an ammeter, then use the one on your charger if it has one. Clip it on to the battery cables (no battery) and see what the car is pulling from the charger while turned off.
If you really don't have an ammeter, you can at least try unplugging the battery overnight and see if it still goes dead. If it does, replace it. If not, it's the car and you'll need to test further to narrow it down.
cvxjet MAY 13, 03:48 PM
It happened again.......What things draw power? I do NOT have pwr windows, door locks or mirrors, no AC.......The only things I can think of are A) The computer draws a very small amount (Normally!), B) the headlight motors are always connected (But I did not run them at all) and C) the courtesy lights....I will be watching the courtesy lights from now on to make sure they turn off when I close the drivers door...

What else could draw power after turning off the car and removing the key?
2.5 MAY 13, 04:37 PM
That quickly I would think headlight motors first as well, could try leaving them, or one of them unplugged and see if it happens again.
JMTUT MAY 13, 05:18 PM
I agree with unplugging the lights. That is the first place to look. In rare cases, the alternator diodes can go bad and drain the battery also. You can unplug it overnight also if the headlights turn out not to be the problem. You can check for draw using a cheap meter from Harbor freight. It will blow a fuse if the amperage is too high though.
fieroguru MAY 13, 05:57 PM
Check to make sure the brake lights are not on. The switch can get bumped...