OK guys, after what started to be a great Father's Day weekend, the car totally stumped me yesterday morning, as well as **** me off. You're all going to love this one.

The Gremlins actually appeared when I got the car in February. The interior lights would never come on when you opened the doors, but they would illuminate when I opened the rear hatch. I checked all the fuses and all were good so I let it go to concentrate on getting the horn to work (had to remove the steering wheel for that one). Anyway, mysteriously afterwards, the lights started working again like they should until Saturday night when they wouldn't come on again. I checked the fuses again and all was in order.

Now here comes the best part. About a month ago I kept blowing the 15 AMP fuse for the radio/pwr door locks/interior lights/ etc. everytime I hit a pot hole (its like CHK or something on the fuse box). I thought it was a short in the radio, but then it happened without the radio being on yesterday and now whenever I try to replace the fuse, it instantly blows out. I noticed now that the Security Light is no longer blinking as well.

So any ideas guys? It seems like there are 4 separate systems linked to that fuse and all are tied into the Security Module in some sense. Has anyone experienced a failure of this module and what were the symtoms? With something like this, it could take forever to find which item is grounding out so I want to start at the most likely place.

Any suggestions would be appreciated.

P.S. A happy belated Father's Day to all you Dads in the Forum!

 

Your interior lights didn't come on because the door jam switch or its ground was defective. Fuses blow because of excess current. The door locks get power from a wire that goes through the body into the door and these wires flex every time you open and close the door. That is the first place I would look for worn insulation and a wire touching the body causing a short. Otherwise you have to trace every circuit on that fuse to find the short. You can replace the fuse with a 12 volt lamp and use a d.c. clamp on ammeter to trace which wire is carrying the lamp current and that is the one that is shorted to ground.

 

Looks like this isn't going to be a fun process. What are the odds of the Security Module relay causing these malfunctions however?

 

Well I looked at both doors last night for any signs of wires grounding out and all I found was a disconnected plug with 2 wires (white and an orange/white wires) which I am pretty sure go to the driver's side courtesy light (which my car is apparently missing), everything looked fine. I'll probably pull the door panels off next for a more in depth look later.

I also put a voltmeter to the "faulty" circcuit in the fuse panel and it reads 12.6 volts however, I don't know what the amperage is. I test light reveals that power is only on one contact, as it should be. I tried to install a new fuse afterwards and it blew instantly. I was always told that if there was too much amperage to a circuit a failed relay is likely the cause. Any thoughts?

 

sorry but i would say join the club!! QA at GM wasn't the greateat back then!! i took a tour of the Bowling Greens plant in 1998 and they said NOW they QA the ***. line every 10 parts that are added to the car. they didn't do that when our C4 were made.

 

You should start at the power source for all the circuits. You could try the relay you mentioned if it feeds all those circuits. Otherwise start disconnecting connectors until the fuse doesn't blow, to narrow it down to the faulty curcuit.

 

Thats exactly what I plan to do, I have started doing that already. I looked over the wiring diagrams and couldn't find one for the power antenna, does it also get powered from the CTSY/CHK fuse? I was having problems with it and wonder if it caused the whole thing.

 

Well my hunch was right, it was the power antenna causing the whole thing. The white wire to the antenna was grounding out. Fixed that and problem solved!

Now I need to figure out why the courtesy lights still dont come on when the doors open. They work from the main light switch on the dash and I can turn the map lights on in the doors, but other than that, they're dead, and the halo lights work when I open the hatch. I'd say its the pin switch in the door jam, but that must be working because the security system knows when the doors are open and closed because it arms normally, unless another switch controls that. I was thinking of the timer that dims the lights after you close the doors, any ideas?