About every 6 months I end up with a dead battery after sitting for a few days. This afternoon it happened again. Here's the routine:

Get in car, try to start, not enough juice to start it. Fast charge battery about half way (always can hold hand on battery for heat check). Start engine, volt meter in car shows about 14.5 V. Run car for an hour or so, volt meter is usually about 14.5, sometimes drops to about 13, back to 14.5... Restart, drive again, same reading on volt meter, stop engine. Fully charge battery on regulated low output charger with charge testing (maybe about 5 ~ 7 A average?).

Check battery with electronic tester (don't have load tester), tests as "less than perfect", but not bad.

I find that there is no drain (amp meter on battery lead), and charging voltage looks good on meter too.

Costco replaces battery for just a few bucks, no questions asked.

Wait about 6 months, repeat... Three times now.

Any ideas at all?

I suspect something is intermittent. Voltage regulator, some connection somewhere, bad ground, etc... but only every 6 months or so?!?

Or are the recent Costco batteries that bad? Before this current problem run, I had one in there for about 5 years or so.

Just a couple of weeks ago, I ran a Battery Tender 0.5A float charger on it overnight, it was "green light" condition in the morning.

 

 

Late at night, when all is quiet outside, place ear on hump in trunk and listen for fuel pump running with key NOT in car. It's a longshot, but the Oil Pressure Sending Unit can go bad in such a way that it makes the fuel pump run constantly regardless of the key.

 

Get a load test from Auto Zone, Pep Boys, etc. It's free!!
Have you added anything electrical?

 

Get a load test from Auto Zone, Pep Boys, etc. It's free!!
Have you added anything electrical?

Old trick--
With the car idling, put the metal part of a screw driver against the center of the rear of the alternator--a magnetic pull will tell you if it's working.
Be aware of belt(s) and be careful if you try it--don't want to have the thing pulled out of your hand!

 

Since my last post the following is current status:
- Battery load test - OK
- Alternator check - OK
- No further dead battery so far (about 10 days)
- I have been watching the in-dash volt meter like a hawk, and sometimes see it dip as low as about 12.5 V. This is rare, and on HOT days (my guess, need more cool days to observe and make sure, but weather is not cooperating). Usually it's between 13.5 and 14.5.
- Many years ago I added a CB radio, been dormant for years, wired to switched wire, only on when main switch is on.
- Many years ago I added a radar detector, also wired to switched wire.
- No solution found yet.

 

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Marked ?!?

 

It means that I am following this thread without adding comments

 

Now I understand.

I found a "no charge" situation this morning, so I installed a new alternator, 125A I think...

Seems ok for now, anyway.

Time will tell...

 

Replaced the battery terminals, starter cable, and large earths yet? If they're still the originals, something's probably getting a bit crunchy after 20 yrs. Had this happen to me, though my time between fails was weeks, not months, but w/e.

Ignore the dash voltmeter, that's just for giggles - use your multimeter right on the batt terminals - do you have 12-12.5V at rest, 14-14.5V while running?

 

All the cables are good. The car only has about 75000 miles, and spent a large part of it's life in the garage. Also recently checked by an auto electric place, and a trusted shop about a year ago.

Voltages are as you say - 12.6 no load, about 14+ running.

Thanks!

 

UPDATE -
I found what looks like a relay in the "trunk" next to the lid latch area. (NOTE: I got tired of replacing the motor housing every other month, so rigged this into a solid slam latch.) This whateveritis is quite warm, but not hot, after car sitting overnight. I disconnected it, and everything still works without it - except the hatch motor, which I don't use any more.

So now - what is it? It was stuck onto the back metal wall, just below the lid latch on the right (from front) side. It's an original part. It is marked 20650336 0320-5. Lead wire colors are white, blue, black, brown. All are "doubles" except the brown.

What does it do, and why would it be warm with all surrounding items cool, all switches and main switch off? What should I do next? I will leave it disconnected for now.

 

that sounds like the trunk pull down relay, is the white wire a white wire with a red stripe?

 

I'm pretty sure both those are just plain white. I can't easily check it right now, I already buttoned up all the covers, etc.. If it makes a difference, it's a 91 T/A.

I have discovered it is a relay, and it is right by the hatch closer motor area.

So now the question is - Why was it hot, electrically? Shouldn't this be triggered only by the hatch latch bar as it is moved to the down position, and then off when it's fully closed? What normally kicks it off? Probably it was on as a result of my modification to make the hatch closing manual, and didn't disconnect something I should have? Or maybe it's just a stuck "on" relay?

 

it could be that its trying to pull down the hatch even though the hatch doesnt move down now. so yea possibly a "stuck on" situation.

 

What triggers the latch circuit to activate?

 

theres a little switch on the pull down unit

 

So if the "slider" was held permanently a bit short of it's full stroke, the switch would always be on?

Do you have any idea of the current the primary side windings of the relay would draw?

 

yes, if the hatch motor doesnt think the hatch if fully closed because of that switch, then it will stay on either trying to pull it down or lift the hatch slider up, depending on which way it thinks its trying to go. it been the cause of many a dead battery on our cars. usually is because the plasitic gear in the hatch pull down assembly is stripped and the motor doesnt actually move the assembly. causing the motor to continuously spin and drain the battery.

as for how many amps it draws, that i have no idea

 

Sorry to bring this up but the same thing happened with me. i bought a new duralast gold battery and it kept dying after around 3 days of not using the car. turn out my hatch motor was constantly trying to close the hatch and that caused my dead battery. i just unplugged the motor and ever since then ive never had a dead battery. it took me a few months to figure it out. i had went through 3 new batteries from autozone. im trying to find a hatch motor casing so i can replace my old one since the threading where the bolt hold it to the frame broke in half. im sure once i get it installed that will fix my hatch problem

 

For your hatch motor stuff, and lots of other goodies, go to

http://www.top-downsolutions.com/