Dimmer Switch Strikes Again

[cotto]

Alright, my 93 W250 is also having headlight problems. All the sudden my headlights stopped working after a long trip. After investigating, I found that the switch and the wiring harness' plastic plug had melted. The other lights are unaffected. I can run all other lights without a problem. I replaced the switch, only to have the new one melt within months. I have read the threads about how to rewire the headlights with a relay, but I am wondering if anyone has figured out what causes this issue. Are there any usual suspect? I would like to fix the problem, not just bypass it if possible. I had 255K without a problem. Now I have melted two switches within 7K.

Also, I looked into replacing the wiring harness' plastic female plug, but NAPA only has one for '94. Does anyone know if this will work on my '93?



Thanks

 

[JGrefenstette]

yea pete told me the 94 switch will work on the older ones. have you added anything to your switch at all??? gauges, tach, marker lights, trailer lights, anything at all???

 

[cotto]

Unfortunately, I have not added gauges yet. They're on the list. Everything has been the same since I bought the truck 9 years ago. The problem did start about nine months ago after towing a buddy's ski boat, but I had pulled many boats before that. I'm wondering if the ground to the switch could have gotten bad. Do you think this would casue such a problem. Thank you for your reply on the switch. Do you think the wiring harness' female plug would work with the 93 switch?

 

[JGrefenstette]

when you load/unload the boats does your rear get in the water? if you submerged some of the wires in the rear i can see that it may have caused some issues. if it was shorting out somewhere it would make sense that it could be inturn overloading the dimmer. yea im pretty certain the plug is the same. hopefully pete will chime in here... .

 

[cerberusiam]

If your melting the switch you have a bad connection somewhere. Too much resistance to the amps running thru the switch will cause this. You need to start back tracking the harness to the lights and pulling every thing apart. Scrape clean and coat liberally with dielectric grease. Do the same for the grounds as they could be the root cause also. Good luck.

 

[cotto]

Thanks guys. I really appreciate your ideas. It sounds like this weekend will consist of a knife, a flashlight, and a half rack.

 

[PToombs]

Dimmer switch? That's kinda unusual. Usually it's the headlight switch that gets hot and melts. If that's it, the problem has to be in the headlight circuit.

If it's the headlight switch, the 94 and up had a better switch, and the plug is available also. If you changed the switch and not the plug, the bad connection on the plug melted the new switch. Resistance is heat.

The switch won't take much extra load, that's why people add relays in. Did your buddys boat trailer have a lot of lights on it? If so, that may have created the heat that started it all.