What would cause one fog light not to work (bulb is good)?
I have a 2006 Ford F150 Lariat. When I turn on the fog lights, the drivers
side comes on but the other does not. I tried switching the bulbs and still
the drivers side comes on and the other doesn't; so I know it's not a bulb
problem. The connectors are clean and the wire harness looks good. What
could the problem be? Could a faulty relay somehow still allow one to work
and the other not?
I would check for voltage at the light that does not come on. If there is voltage then I would suspect a bad ground somewhere near the light.
check all wiring in the fog lamp unit for corrosion around all electrical connections
Bad connections at the bulb. Fog lights are down low where they get water and dirt on them. Clean the connections and the socket where the bulb fits. Wiggle it around a little and you will probably see it light up.
Use a multi meter with pointed probes and slightly pierce the wires directly behind the socket which does not work. If there is 12 volts there, then replace the socket. They are usually available at various auto parts stores for your particular make and model. They come with pig-tails to make the connection. I suggest you use shrink warp tubing over the connection points and follow up with a little electrical tape if that is the problem.
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