Battery draining

[knuckle ears]

93 Pontiac Transport 3.8

I have a problem with my interior lights coming on in the middle of the night and draining the battery. Is their a module or device that normally does this when you open the doors? the lights normally come on and then when you close the door they stay on for a bit and then dim and turn off.
The vehicle has the optional illuminated entry system and remote keyless entry. when you press the keyless remote the interior lights will come on for about 40 seconds and then go out if you don't enter.

I have removed the batteries from the remote to see if this is causing it. the wifes vehicle has a remote start and had a bad micro switch in the remote clicker. It would turn the head lights and tail lights on in the middle of the night and kill the battery. I replaced the micro switch and problem is gone.

[LMP]

I keep that OFF by flipping the switch near the cigarette lighter.
The lamp timer is part of the keyless entry module....

[knuckle ears]

Still having battery/ maybe alternator problems.
If I put a trickle charger on it over night the battery is good for a few days. Then it is dead. I lokked for a staedy drain with a test light and none found.

If the alternator is good, shouldn't the battery charge up when i am driving it just like a trickle charger does, but faster?
I am thinking it is an alternator problem.
Any ideas?

[kb0nly]

Go to somewhere like Batteries Plus or AutoZone, a lot of them will load test the battery before buying a replacement.

Sounds to me like a bad battery, but to double check, make sure that when the engine is running your seeing 13-14v at the battery terminals from the alternator, rev the engine a bit, see if the voltage changes, etc.

I had a problem on mine that i thought was the battery, turned out to be the alternator's sense wire to the battery through the underhood fuse panel had a break in it. The alternator uses that sense wire to determine what the voltage is at the battery, taking any line loss into account for the heavy gauge wiring from the alternator to the battery. Most GM products are like this.

Anyway, i was seeing anywhere from 11-15v from the alternator, fixed the sense wire and see a steady 13.6-13.8 most days, around 14.1 if i left it sit with everything on and the engine not running for a while, think of that as a quick charge, and then it drops to the normal 13v range for float charging.

A battery is a heck of a lot easier to replace than the alternator, so check everything before digging in! And if you do have to replace the battery don't skimp, go with a good name brand, i prefer Optima myself.

Oh on another note... When the battery voltage dropped down to around 11-12v the computer and keyless entry system would do nutty things, perhaps your battery voltage is sagging low enough to screw up the entry module and its turning the lighting on.

With the float charger on the battery overnight did it ever turn on the interior lighting again?

[knuckle ears]

where is the sense wire and fuse panel under the hood. I can't seem to find it.

The interior lights don't come on anymore because I switched it off at the switch near the cig lighter.

[kb0nly]

I just realized you have a 93, i have a 97. The 97 has an underhood fuse panel that sits over the battery, there is a 10amp fuse for the alternator sense in there.

So unfortunately its probably different on your 93 then.

[LMP]

ANyway...a suggested by KB, take a voltage measurement when the engine runs..anywhere, at cigar lighter, at main pole near brake booster (red plastic cover: should read near 14 v...anything between 13.5 and a little over 14 will do. If under 12V, you have an alternator problem.
WHat is age of battery? Worn out batteries behave like that.

[knuckle ears]

Took a voltage reading across the batery terminal when engine running. It was 14.7 v.
Not sure of the age of the battery, it came with the vehicle last year when I bought it.

[kb0nly]

If you got 14.7v when running than the alternator is working hard to bring that battery back up to fully charged. I saw the same symptoms on mine when the battery pooped out.. The voltage would sag really low with the engine off, but 14.5-15v when it was running, popped in a new battery and it went back down to 13.6-14v when running.

Get a new battery, i'm betting that's your problem. If you have a place like Batteries Plus around they will load test your battery also, but my bet is replace it and forget about it.

[LMP]

I agree with KB that 14.7 volt is suspect and indeed 98% points to a worn out battery: the worn out battery has a high resistance and this is what causes this high voltage when charging, not a high current rate: an ammeter would probably show a very modest charge. I will let you go without the textbook calculation....anyway this is for the fun of talking: bottom line: install a new battery..in doubt (2%) , borrow one KNOWN as good for a 2 day test....sometimes reality can invent new things...but not often....

[knuckle ears]

A new battery looks like the way to go.
Over the years I have replaced alternators thinking that was the problem but it was the battery. Also changed batteries and it turned out the alternator was no good.
Thanks for the help, let you know how it goes.

[knuckle ears]

Replaced the battery a couple weeks ago now and all is well. Voltage is 13.7 to 14.2.

thanks for the help again.