Need some help here. I recently purchased a 1990 C4 Cab with just under 20,000 miles on it. The car has been babied and pampered for the last 15 years with every possible maintenace and repair item addressed including flywheel and engine resealing. The car has a history of battery problems. Something is causing a power drain that saps up the power in the battery. If the car sits longer than 2 days, the battery is dead and needs to be jump started or charged. Past mechanics have noted the starter and alternator are ok. Has anyone experienced this problem or has any thoughts on what to check. Other than the alarm and clock, I am not aware of any other circuits in the car which might be the culprit. The car has an aftermarket Alpine radio installed and I know that their is a switch of some sort that was attached to the factory unit that was connected to the alarm. If this was not reinstalled or dealt with, could this be the culprit. I thought about pulling the fuses to the radio and alarm system to test this theory. If anyone has some ideas on what I should check before I head off to my mechanic that would be very helpful.

 

I experienced a similar problem on a 92 C2. The problem was the rubber boot covering the door switch. Whenever you park the car and shut off the engine, the car keeps power applied to a few critical circuits (e.g. electric windows enabling them to be raised after the engine is shut off.) My problem was whenever I shut off the engine, I would open the driver's side door, get out, and close it before the rubber boot (which had stiffened with age) allowed the door switch to extend completely. It is that door switch that tells the electrical system that you are "done inside the car" and kills power to those final circuits. Consequently, I was getting out and going into the house with those circuits remaining charged. After 2-4 days, my battery would be so drained that the car typcially would not start. You can test this by leaving your window down whenever you shut off the engine, get out and close the door, and then reach back inside through the open window and see if the window will raise. It should not if the switch is working correctly. If you're still unsure, simply remove the rubber boot and try it for a while just to see if the problem goes away.