I seemed to have developed an electrical problem in my 1989 C4. I am trying to trouble shoot. Here is the story, sorry if it is long winded, but I do not want to miss a pertinent detail, I know cars, just not pcars:

I took the car out yesterday in light rain. Everything was fine. I went out in more light rain that evening and it was fine. I did get a Check Engine light about 100 feet from my house. I checked the engine, but did not know what I was looking for. I did not put a cover on the car like I usually do because it was soaking wet. It drizzled most of the night. This is the first time since I have owned the car it got rained on overnight.

I fired the car up this morning under moderate rain with no problem. Less than a mile from the house I started losing electrical power, the wipers slowed down, engine power was down, and the radio quit. The idle went from the normal rock solid 880 to hunting around 1,500. Overall the car was running poorly. The car then threw a Check Engine and Brake Pad Sensor warning. I forgot the warning symbols and misread the Brake Pad Sensor warning as an alternator due to the electrics. I stopped to check the belts and they were fine. I decided to just go home, but after the stop the car ran perfectly so I went to the grocery store with indoor parking. 20 minutes after shopping I tried to start the car and the battery was almost completely dead. I got a jump and it was fine. I drove home in the dry and parked. An hour later it started like a champ.

My thoughts: The battery is new and works in the dry, so rule that out. I looked for sparking ignition wires, I did not see a spark so it is probably not shorting there. The alternator works enough to run the car (unless it is raining a lot), but not enough to charge the battery in the rain. The drive home from the store is 3 miles. I do not understand how an almost completely dead battery could be charged after less than 10 minutes of driving. I did not hear the alternator belt slipping in the rain, but I am not 100% sure I would have over the engine noise. It seems as though that alternator works in the dry, but not wet. Is there a place it could be shorting with water.

Does this sound familiar to anyone? Is there a known problem/fix with the alternator and rain? Where should I begin testing, specifically the alternator? What does Check Engine mean?

 

Is your alternator charging the battery? I would check the voltage at the battery with the engine running. It should be between 13-14 volts.

 

Thanks. I assume the alternator is charging. It usually starts no problem. I will check to see if I am getting the full 13-14 volts.