The Stovebolt Site Forums The Shop Area The Electrical Bay new light switch issues

In an effort to get my dome light working again on my 55.2 GMC, I purchased a new light switch. Today I ran new wires to the dome light and replaced the light switch. I took great care to replace all the wires on the new switch in the same location as the old one, but when I finished my brake lights were on and wouldn't shut off. Also my 3rd brake light was not working at all. After doing some mickey mouse work I hooked up the brake lights to a "switched" connection on the switch and everything works fine, as long as the lights ore on. With lights off, I have no brake lights, and I still don't know if I fixed my dome light. So I either drive around with my park lights on, or somebody has an answer to my problem. I'm betting it's going to be something stupid that I did wrong, that's my standard mistake.

This one shouldn't be too hard. If you have the factory manual there is a good picture of the light switch that shows what each terminal powers up. Even if your new switch is not exactly like the factory one, you can put power to it and pull the rod out to the 2 positions and see which terminal has power in each position.

I get everything you say, but, everything worked before the change except dome light. It was in the reostat (sp?) on the switch. I'll try a new wire to the brake light switch and see what happens. Thanks.

The dome light works differentley then most circuits. Power goes to the dome light all the time through the fuse block & shares a fuse with the stop lights. The other wire to the dome light is grounded through the light switch or door jam switches if equiped. The light switch must be mounted in the dash to be grounded. If you are testing with the switch hanging it will throw you off.

Your brake lights were on all the time, now they only work when the parking lights or headlights are on. The good news is that your brake light switch is working and your wiring to the brake lights is good. So something you changed made a difference. Find the terminal on the headlight control switch that sends power to the brake light switch without having having the parking or headlights on. Since you know the rest of the circuit is working that should give you proper function of the brake lights.
I see that your truck is a second series '55 and I don't know if it's wired the same as my '48. On mine the terminal adjacent to the brake light terminal is the one for the dome light.

Well, after some lost sleep over night, I went after my switch again. Armed with my 12v tester, I was able to go through all the connections on the switch and figure out that I had 3 or 4 wires in the wrong place. Seems the new switch has a slightly different layout than the original. With some choice words and a few names aimed at myself, I now have everything working the way it's supposed to. Thanks for all the help. The H4 lights and new LED bulbs everywhere, the difference is surprising. Now to get a bulb for the dome light and ruin my good mood!

And after all of this to get the dome light working, it doesn't! But everything else is, I'll take it.......for now anyway.

In an effort to bring this to a close, I replaced the bulb socket in the dome light and I now have EVERYTHING working the way it is supposed to. Thanks for the help, now what will be the next thing, because we all know there is always something else.