98 Cavalier Electrical Problem

[tobymix311]

My cavalier has developed a strange electrical problem. The map lights, dome lights, and power mirrors all stopped functioning. I checked the fuse, and it's good. I've tested the fuse block with a volt meter and I'm not getting any power to that particular fuse. I pulled the whole block out and none of the wires are severed. I'm fresh out of ideas. Anyone have any suggestions?

[DannMann99]

follow the wires. youll probably find the problem

[Tookie]

Retrace the related main wires that feed the block and do a continuity check of those wires.
CAUTION!!
Make sure the battery is completely disconnected; or you'll likely blow any protection fuses in the meter (or the meter itself!)
One probe on one side of the block's hot side connector, and use a very fine needle probe to pierce the sheathing on the related wire(s). Do the same with the ground connector, and this time find a common ground point. You should have continuity on each independent loop. Recheck the fuse for continuity also. Work backwards from each wire probe till you lose continuity. Means a seriously pinched or disconnected wire wherever you lose continuity. You may have to trace the related wiring all the way back to the firewall entry point an inch (cm) or so at a time. Be patient, and don't turn into one..lol Look for any defective rubber grommets where the wiring passes through sharp edging and shorts to metal.
There is a way using capacitance measurements; but that would require some accurate specs on the wiring etc.

Tookie

[tobymix311]

Originally Posted by Tookie

Retrace the related main wires that feed the block and do a continuity check of those wires.
CAUTION!!
Make sure the battery is completely disconnected; or you'll likely blow any protection fuses in the meter (or the meter itself!)
One probe on one side of the block's hot side connector, and use a very fine needle probe to pierce the sheathing on the related wire(s). Do the same with the ground connector, and this time find a common ground point. You should have continuity on each independent loop. Recheck the fuse for continuity also. Work backwards from each wire probe till you lose continuity. Means a seriously pinched or disconnected wire wherever you lose continuity. You may have to trace the related wiring all the way back to the firewall entry point an inch (cm) or so at a time. Be patient, and don't turn into one..lol Look for any defective rubber grommets where the wiring passes through sharp edging and shorts to metal.
There is a way using capacitance measurements; but that would require some accurate specs on the wiring etc.

Tookie

I did something similar. I have a tone generator and a probe I hooked up to the lines. I traced the wire clear through the dash and right to the firewall without any troubles. Once in the engine compartment though I ran into some trouble. I can see where the wires come through, but I can't get to them at all. Visibly the wires look fine, nothing bent or broken. Is there any kind of relay or breaker that may be the trouble?

[Tookie]

I'd have a close look at the wiring that feeds the motor/actuator assy to the power mirrors next. though I'm not sure of the specific diagram, it's possible there may be a bad set of contacts that feed-thru the assy and related components.
Assuming theres an ingress/egress circuit that controls a relay connected to the dome light assy, it may be a lack of trigger signal from that specific chip or circuit. Check also, any wiring that feeds from the body to the door's mirror and motor assy.
One sure way to see if it is a CPU error is to disconct the batt for a bit and go through a reset. Be careful though; as you'd want to know what will be affected on pwrdwn, and how to recover normal vehicle functioning afterwards. Theft protection, ECM etc. And of course you could have a partial bad relay somewhere in the mess of things.


Tookie