93 regal battery discharges overnight (sometimes)

Hi all.

i have a 93 regal and the battery discharges overnight randomly (sometimes). i can leave it parked over the weekend and works fine when i start it. but other times it wont start the next morning. jumpstart works fine so its not the starter, plus the door locks are barely moving (or not at all) when the battery is drained.

this is happening about 2-3 times a month winter or summer. battery was replaced at the beginning of 2007 exactly because it was draining and i assumed it needed a new one, although it tested fine. contacts on the battery are clean and covered with vaseline to avoid corrosion. last cleanup was done this month (june08) and yet a few days later it wont start. alternator changed at the beginning of 2008, assuming that it was bad - but no fix. checks at autzone/murray show both alternator/battery are fine.

i checked the "idle" drain (put Ammeter in line with battery negative) and it's about 0.30-0.45 amps (300-450 mA) - which i assume is caused by the computer and (aftermarket cdplayer) radio. i've had the car since 2004 but it started doing this end of 2006 - beginning of 07.

nothing was added/removed from the config. cdplayer/radio was there from the beginning. it has a remote entry system but i never used it (only tried once and it locked up so badly the car wouldnt start until i removed the negative). the remote control is in a drawer without the battery inside so that cant be it either. all interior couresy lights are removed just to make sure they are not the cause.

i assume it could be smth that is happening from time to time like a loose wire thats "always hot" or some module that shorts out, maybe even a fan that turns on at random and drains the battery.

any ideas where to start? i thought of maybe some wires in the driver's door (since the other doors stay closed all the time) which would short after getting out of the car.

help is appreciated!

Since it only happens on an occasional basis check things like the glove box light, trunk light and possibly the interior lights. I had a problem with an intermittant glove box light that kept draining my battery. I finally removed the lamp and haven't had an issue since.

Just an idea!

Since it only happens on an occasional basis check things like the glove box light, trunk light and possibly the interior lights. I had a problem with an intermittant glove box light that kept draining my battery. I finally removed the lamp and haven't had an issue since.

Just an idea!

the glove box is the only light still left because i couldnt easily pull it out... i've already taken out all others. might as well give it a try. thanks!

EDIT: i removed that light too. so no more courtesy lights. as i see from the schematics the only other things "always hot" are the ignition and door locks (which includes the keyless remote).

any other suggestions?

If you haven't changed the positive and negative battery cables change them. Sometimes internal corrosion will cause them not to want to transmit voltage well and therefore could be causing what we think is a drained battery but may not be dead at all only high resistance caused by corrosion.

If you haven't changed the positive and negative battery cables change them. Sometimes internal corrosion will cause them not to want to transmit voltage well and therefore could be causing what we think is a drained battery but may not be dead at all only high resistance caused by corrosion.

the battery cables are both "new" - replaced in 2007 when i replaced this battery - mostly because one of them had a screw so badly torn i couldnt remove it from the old battery. i also measured resistance with the negative off when i changed the alternator this year (because i was assuming the issue is "not charging") and its only a few ohms so it should be fine.
the battery gauge shows just above the 13 mark when the car is running and just below 13 when i put the key in (on the days it will start fine). its lower when it wont start...
thanks again! other suggestions?

my 94 was having this same problem it turned out to be a bad case of corrosion where the cable from the battery connected to the main fuse box, so my easy fix would be try cleaning off that junction

my 94 was having this same problem it turned out to be a bad case of corrosion where the cable from the battery connected to the main fuse box, so my easy fix would be try cleaning off that junction

ok thanks i'll look at that altough it hasnt happened again since i posted this message...

ok thanks i'll look at that altough it hasnt happened again since i posted this message...

nope did not see any corrosion around the battery wires...