I have an 03 blazer and the interior lights wont go off. Is there a way to test the door switches? If I unplug the bad switch should the lights turn off?

 

Have you checked the switch on the dash by the light switch? Adjusts the instrument panel lights and also your interior lights... Just a thought...

 

Well, depending if it's a NC (normal close) or NO (normal open) logic. But easiest way is to hook up the voltmeter to the switch contacts. In one position You shall see the voltage (open), the other one it would be gone (closed). If that won't help please post the year of Your truck.

 

On the second gen S-series trucks there are 2 different door triggers. One is built into the door handle, and the other is a pin-switch on the side of the dash that contacts the door when it is closed. Most likely the problem you are experiencing is with the pin-switch on the side of the dash. Quite possibly the pin has been broken off, making the truck think the door is open. You can unplug the broken switch and the lights will go off as the switches are N/C type. The switches are really cheap and easy to replace. The switch pops out, and it's a 2 wire harness off the back. You may have to get a hand inside the dash to compress the tabs on the side of the switch if it won't pop out easily from the outside.

 

it's an 03