Help Me Trouble-Shoot my Factory Hella Fog Lights

[Sherwood4Runner]

Since I've owned my 4runner (almost 2 years) my fog lights haven't worked. So, today I set out to fix them. I have a decent knowledge of automobile wiring from installing car audio systems in a few previous cars, so how hard could getting some fog lights to work correctly?

The Problem: Passenger side fog light is drawing an incredible amount of amperage causing fuse to blow.

If I just hook up the driver side fog light the system works, but if I plug in the passenger side the fuse blows instantly.

-Voltage at fog light switch is normal
-Voltage at fuse is normal
-30Amp relay is still functioning properly
-Bulbs are still good
-Amperage at passenger-side fog lamp exceeds 20amps during malfunction (Yikes)
-Amperage at fuse (In-between battery + terminal and relay) exceeds 20amps during malfunction

I pulled all the wiring and inspected it and it all looks good. While the wiring was all pulled out I hooked it back up to the fog lights to try it again, and they both worked!!! Then, to my dismay, after re-installing the wiring and lights back where they were on my truck the previous problem RETURNED.

I suspect a bad ground somewhere because of the inconsistency, but i wiggled the wires a lot while the lights were working and had no issue. Any ideas guys?? Corrosion in the wires maybe?

 

[Jaynhunt]

Could be a bad ground but the highly technical wiggling usually points that out. Sounds like a short. I'd replace the wiring and call it good to eliminate the major source of problems.

 

[ryankmasuda]

I had the same problem last weekend with my passenger side fog light. I pulled both fog lights and disassembled the entire thing. Blew compressed air to remove any debris and water and let it air dry for 15-20 minutes. I then blew air in the connectors to get the water and debris out. Let that dry and put dielectric grease in the connectors. I ended up replacing the wiring inside the fog lights and put everything together and I no longer blow fuses. I also put silicone in the dust cover vent to keep water out. I think the main issue is water getting inside the fog light. Since we get so much rain up here I think most of the fog light problems are due to water and the vent design on the dust boot.

 

[Sherwood4Runner]

Thanks for the tips guys. Ill try cleaning out the connectors and replace the wiring inside the fog light to start with. The connection point for the ground wire inside the fog lamp was fairly rusty so that could be the issue at hand.

If all else fails...I'll just re-run new wiring from the relay forward...

 

[shadow247]

Thanks for the tips guys. Ill try cleaning out the connectors and replace the wiring inside the fog light to start with. The connection point for the ground wire inside the fog lamp was fairly rusty so that could be the issue at hand.

If all else fails...I'll just re-run new wiring from the relay forward...

Rust on the ground wire you say? I'd clean that up first before messing with the rest of the wiring. A bad/rusty ground can cause all sorts of issues, the least of which are high current draw and blowing fuses. I have seen bad ground wires actually catch on fire in some newer vehicles.

 

[Thewudd]

Hey...I have a similar issue. My factory Hellas aren't working either. Can anyone pull the switch inside and let me know which wires go where? There are 3. A yellow, a purple, and a black. I accidentally pulled the switch w/o knowing when I was installing my alarm. Thanks.

 

[janefennell147]

I'd replace the wiring and call it good to eliminate the major source of problems.