Interior Light, Volts? Options

[EdwardBlume]

I'm getting 5-6 volts at the interior light. That can't be right can it?

Any ideas on how to get it up to 12?

[Dave_Darling]

The door switch wires are not always hot. They can be, if you have the light switched to the "on when door open" setting.

Rob, I can't picture what you were measuring. Please describe in more detail?

There is a black/red wire that is always hot going to the interior light. There is a brown wire that is always grounded. There is also a brown/white wire that is grounded when either door is open, because it goes to both door switches.

Did you unplug the black/red wire and measure to a known good ground? The battery post would be ideal, but some bare chassis metal will work. That is measuring just the path to get the power in to the light. If you measured 6V there, you have some very dirty connections or other high-resistance things going on with that power path.

Measuring between the black/red wire and the brown wire tests the whole circuit for the light. (Unplug the wires from the light to do this test; if you leave them plugged in you can get odd readings. Or at least remove the bulb so you don't have a direct path from + to ground through the bulb.) Getting 6V here, if you got 12V on the earlier measurement, means the ground path is messed up. Some high resistance connection, or going through some other component--light, motor, resistor, something.

Repeat the test with the brown/white wire with each door open. Again, if this is 6V and the others were 12V, there is a lot of resistance in the circuit. The switch for the open door is the primary suspect at this point.

You can also use the ohmmeter function on your multimeter to see what kind of resistance you get from the brown and brown/white wires to a good ground. Should be very low.

My first guess is that your measurement was actually the voltage dropped by the bulb, and that everything is OK. But I could be wrong.

--DD