strange fog light switch problem

eruddick · 01-19-2018, 10:54 AM

My fog lights, mounted in cutouts in aluminess front bumper, used to work fine. Sometime last year they stopped working. I've checked the bulbs (not leds) and they are fine. I also have rear fog lights which work fine. Checked the fuse and it's good still. The switches for both are located on the lower dash on the driver's side, to the left of the steering wheel. I switched the wires from the front lights to the switch for the rear lights and then the front fog lights worked. So I figured the switch went bad. So I ordered a replacement (pack of 3), installed it, and the front lights don't work. I tried another one and it doesn't work either.

The switch for the rear lights has no LED. It is a SPST round rocker switch, and it has 3 connectors. The one for the front lights has an LED and is also a SPST round rocker, with the 3rd connector being connected to ground. I've looked for SPST round rockers with no LED, but they only have 2 connectors. The 3rd connector being for the LED apparently, and it is to be connected to ground.

So, I'm not sure what to do, and why the lights would work with the one switch and not the other. Any ideas?

Ed

**BroncoHauler** · 01-19-2018, 11:05 AM

Each switch likely goes to it's own relay. The relay lets the full voltage go directly to the lamps, vice going through the switch itself. You probably have a bad relay and need to swap it out. Easy to do, once you find it.

Herb

eruddick · 01-19-2018, 11:14 AM

Quote:

Originally Posted by BroncoHauler

Each switch likely goes to it's own relay. The relay lets the full voltage go directly to the lamps, vice going through the switch itself. You probably have a bad relay and need to swap it out. Easy to do, once you find it.

Herb

I thought of that, but it's the wires coming from the switches going to the relay, not the switch. I swapped the wires from the one switch (where they didn't work) to the other switch and then they worked. So, in the second case, the only thing different was the switch. Same wires, same relay.

It's possible could have something to do with the combination of the switch and the relay. Any tips, clues on how to find the relay? I'm assuming it's in the engine compartment somewhere, but don't know where to start looking.

Scalf77 · 01-19-2018, 08:25 PM

How many wires are going to the rear light switch. If it has three terminals and no LED it is a SPDT switch. If they leave one of the terminals open, then it will essentially be acting like a SPST switch. If it has three wires connected it could have two source voltages. You need to meter out the wires and check the voltages

-greg

arctictraveller · 01-20-2018, 11:06 AM

It seems like you don't have the switch connected correctly. Since the other switch makes the lights operate correctly, all your wiring, fuses, relays etc are fine. If you have an ohm meter, simply check for continuity (using the ohm's scale) between the switch connections to find the two terminals that open and close when operating the switch.

eruddick · 01-20-2018, 03:40 PM

Quote:

Originally Posted by arctictraveller

It seems like you don't have the switch connected correctly. Since the other switch makes the lights operate correctly, all your wiring, fuses, relays etc are fine. If you have an ohm meter, simply check for continuity (using the ohm's scale) between the switch connections to find the two terminals that open and close when operating the switch.

Well, Artic Traveller, you win the prize. Just because the new switch looks just like the old switch, doesn't mean it acts the same. On the old switch, when the end with the led is pushed in, the switch is on, and the ground connector is on the same end as the led. On the new switch, both are opposite. Should have checked the simplest thing first.

Thanks for your help...and patience