[logikfive]

On my '99, if I leave it sit over night, the battery is ALWAYS dead in the morning. I replaced both the alternator and battery but the problem still remained.

I've always noticed since winter began it's been SLIGHTLY sluggish to turn over in the morning? I attributed it to being the cold weather. After the first morning start it'd crank over fine and never give any issues.

Now, if I leave it sit for more than 4 hours it cranks over slow like it does only in the mornings and, by the next morning, the battery is flatter than a pancake.

I load tested it and found the draw was coming from my interior dome lights. My aftermarket radio is on this fuse as well, so I pulled the radio completely out of the truck to eliminate that from the system. The draw was still there. I pulled the fuse and the problem is no longer there. The truck starts fine every time, every morning.

So what I guess I'm getting at is, is there a relay or something that could be the culprit or should I look for a shorted out wire? Since I need the truck to get back and forth to work I still have the fuse pulled but since my radio runs off of that I have no tunes! :shock:

 

[MWeed]

I know that this may seem an obvious question, but are your interior lights switched on? The dimmer will turn them on if rolled too far and draw like that. You could also have a bad dimmer in and of itself.
The radio has 2 power feeds. One for operation and one for memory. The light connection enables the radio to dim with the dash lights.
Also the battery could be reaching it's end and not have as much capacity for load as it used to have.

 

[Neil]

Are all of the interior lights on the same circuit? Are any of the interior lights actually on when it's killing the battery? Don't forget to check lights you may not notice that are on like the underhood and vanity mirror.

On my Mustang, the battery was dying and I couldn't find the problem for the longest time until I found it was the vanity mirror lights. The cover wasn't making contact with the switch.

 

[beastofwar]

On our neighbours truck I think it was the glovebox light.

 

[dizzyD]

May check the tailgate light while you're looking (if you haven't already.)

 

[steveg]

I 2nd the motion to check the light under the hood. On my 98 D, it wouldn't turn off, but I caught it in time.