I've had my '87 T/A for almost four years now and throughout it's life as my car it's gone through at least 4 batteries because it just has the habit of draining them for no apparent reason. I always make sure the interior lights aren't on, I've gotten the condition of the batteries I used in it checked when it starts to get a little electronically funky and they're always fine, just drained. My brother and I have bashed our heads against it trying to figure out what the hell's going on it with it, and I need some advice:

I know that GM vehicles from this era have the unfortunate habit of doing similar things, but as all the other cars I/my brother own are either not GM or not third gen, it's something we're having trouble tackling.

Does anyone have any advice on what to check for electrical leaks? Bad alternator, bad battery harness, etc. It's currently winter where I'm at so I'm not driving it anyway, and I thought now would be a good time to start looking into doing some part replacements if they're not too complicated. It's not impossible that it's a "bad battery" every damn time, but it feels really unlikely that I've been that unlucky.

Thanks so much,

- Atomic

 

Have you done a parasitic draw test ?

 

That's the first place to start.

Then, if indeed you have that going on, isolate it down to the circuit(s) causing it, by pulling fuses or connectors one at a time. Keep in mind that all sorts of high-power accessories - power seats, mirrors, windows, etc. - aren't fed through the fuse box; but rather, are plugged into a distribution box above the parking brake release cable. Then once you find the circuit(s) at fault, track them down to find their fault(s).

 

Do the google and learn how to do a parasitic draw test, you'll be the envy of the neighborhood as most won't learn or do it. You;; need a digital multimeter and a battery disconnect. Be sure the battery is well charged. The maximum allowable draw is 30 milliamps. All cars from all eras are known to have problems, most are never diagnosed.

 

Yeah, I've got both of those things already because I know my way around mostly mechanical aspects. Electrical stuff has always been this dark magic and the prospect of even trying to figure out wiring or a new harness has scared me away from it - do you have any sort of online instructions or maybe reference you could share? I don't exactly know how to do it or where to start.

Cheers!

 

If you type "How to do a parasitic draw test on a car" into your searchbar, literally dozens of videos come up in the search. Do this, watch a few of them, and save us all a boatload of typing

 

Quick question:
​​​​​​After the vehicle has sat for several hours (without running) is the alternator warm?

 

I had a similar problem with my 1984 Trans AM. Did the draw test & determined it was the radio. I sent the radio out for refurb & problem solved. Do not remember which push button the the radio was the cause. The tech informed me that the button/switch had corroded & was making constant contact.

 

It's time to step out of the darkness and into the light of practical electrical system troubleshooting.

There are eleventy million YT vids on how to perform a parasitic draw test. Here's a pretty good one:







Yep; something seemingly inconsequential is often found to be the problem. It still surprises me that such a tiny draw as small as maybe just 100ma will kill a fully-charged 700CCA battery deader than 4:00AM.

 

Alice said it best...

"You're as stiff as my smoking barrel
You're as dead as a desert night
You're a notch
And I'm a legend
You're at peace
And I must hide"

You Tube