scottcruss

We bought a used 1998 ML320 that came with Hella front aux fog lights but they don't seem to work. We have have tried replacing the bulbs. Verified that the fuse works (swapped w/ the horn relay). To my knowledge, to use you have to turn on the low lights and press the up aux fog switch on the dash but I can not get them to turn on. I do not get a light that turns on when I press the switch. I get a yellow light if I press the rear fog light. I also believe that the 1998 came stock with them and does not need to have anything enabled from the dealer like 1999 and later.




Am I correct on how to turn them on (low lights and aux fog switch)?
Any other suggestions on how test them?

Thank you.

demichae

Did you check the wiring harness?

scottcruss

I visually inspected the wiring. After verifying the fuse, I tried to test with a volt meter but was not quite sure how to do this w/out knowing if my assumptions regarding how to turn on the fog lights so that power is there were correct.

we47b1me

Since those are not the OEM fog lights, one can only assume low lights + aux switch is how they were wired. Unless you see any other toggle switches? Where is the harness wired to? Should still check for voltage. If the idiot light on the dash isn't turning green when you select AUX, there could be a different issue.

scottcruss

Thank you for your suggestions. Now that I was able to confirm how to turn on the fog lights, I will do some more testing of the wiring, when the weather gets a little better.

we47b1me

I didn't say that was confirming how to turn on the lights -- I assumed but said you needed to trace the wires back from fog lights and see if they come from the headlight wiring harness since you aren't getting the green idiot light on the dash

ygmn

trace wires and sketch connections from bulb to relay to fuse to switch to battery to ground.
everything.

Are you getting voltage at lights any time?
Who knows how they are hooked up maybe previous owner put them on himself and wired funky.

sometimes peeps have them connected to go on with high beams as they could be DRIVING lights.