This is for my internet-less friend so bear with me! The truck is a
2000 model Chevy 2500? dually with a few extra light on the top of the cab, and I believe the fog lights are aftermarket and wired in to the same circuit as the regular parking/instrument lights. This truck has had 3 new light switches replaced as faulty. Each time the switch works fine for a few months then the switch dies again. Quite irritating to the owners. I have the feeling that the switch is overheating due to the few extra lights (especially the fog lights, which definitely should operate using a relay) pulling a couple of amps too many through the switch. Comments on this anyone? Is there any sort of known problems with this switch? It is the 2 position rotary switch, grey plastic knob, found on the left side of the steering wheel. The instrument panel dimmer is not a part of the switch itself. Thanks for any help guys!
On the late model GM trucks, the switch itself doesn't dirctly control the lights. Instead, the switch sends a signal to one of the on-board computers which triggers a relay which turns on the lights in question. In some cases, the switch itself triggers the relay directly which turns on the lights. In very few instances (and as far as I know not in any current GM consumer grade light trucks) does the switch actually power the lights directly. There are no known issues with the current late model GM headlight switches. On some other trucks the headlight switch does carry more than a few amps which can cause heating. This was the common cause for headlight switch failures in the last half of the 80's and well into the
90's on Ford trucks.
Most likely, your friend is trying to pull too much power thru the switch itself which is causing it to fail over time.
Here's what to do (Wiring Basics 101). First, install a relay and fused power cable large enough to supply the aftermarket lights. A relay is nothing more than a glorified electrically activated switch. Tap a line off of a marker light (not a turn signal or headlight) and run it to a separate aftermarket switch on the dash, and then back to the relay. This is the trigger line for the relay. Remember to ground the relay properly.
What this will do is remove the extra load off of the factory light switch completely and allow your friend to turn on his aftermarket lights when his marker lights are on. When his marker lights are off, his fog lights will not turn on at all. If he taps the trigger line off of a turn signal light or headlight, then his fog lights will only come on when the turn signal blinks or appropriate headlight is on (not the best idea).
Interesting sidebar - Recently I installed fog lights on my 2004 Chevy
2500HD (Genuine GM equipment, $125.00 on eBay). All trucks since '99 are already set up in the fuse and relay center under the hood for foglights, whether they came with them from the factory or not. However, the instructions did advise that even if the installation was 100% correct, I still may have to go to the dealer and get the Body Control Computer reprogrammed so the truck will recognize that it now has foglights and allow you to turn them on. Fortunately, mine was already programmed so I didn't have to go.
So if all the light switch is doing is sending a low current to a control module, then how can the fog lights be causing the switch to overheat? i traced the foglights wiring and they are wired completely wrong, they each tap into the parking lights above them (BAD BAD BAD) so i think this is causing my friend's overheating switch... more opinions? thanks J.!
This is just a guess...but in my '03 S-10 the main lights are switched by a relay...the switch in the cab only sends a signal to close the relay. However, it would appear that my parking lamps ARE directly switched from that switch. Judging by the "feel" of the switch I'd say it's pretty light in terms of load it can handle and may be very close to its limits with the parking/tail lights only.
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