fog light wiring - keep blowing fuses

[dlb]

my all trac came with fog lights but the PO warned me that they weren't wired correctly, stayed on when the car was off, and might be a fire hazard. i found one of the bulbs was not just broken but replaced with a totally incorrect bulb--someone had shoved a 194 (typical for dash and marker light applications) into the base of the broken old bulb! replaced it with the proper fog light bulb, rewired the whole thing with a relay, spliced into switched power so the lights won't stay on without the key being in the accessory or on positions, and cleaned the grounds. now the lights will come on for 1-10 seconds and then the fuse blows and i can't figure out why. i read a bit on this and it sounded like the grounds were the likely culprit so i really cleaned the hell out of them, chasing the threads and sanding all the flat mating surfaces, but it hasn't really changed anything. any suggestions?

this is the wiring diagram i followed:

[4wdchico]

I'd cut the loops off the ground leads for the fog lights back a ways and solder/shrink wrap & liquid tape them to some big fat wire that would be run right back to the battery negative.

Or you could just go wild and overkill the whole ground system: Get a ground bus bar from a house main electrical box and pick out a spot on some flat sheet metal that you can sand down to bare metal. Then smear the bare metal with some copper anti seize compound and screw the bus bar down tight to it. Run a fat lead from the battery negative post to the bus bar. Next the real going wild part, run wires from the bus bar to the fog light grounds and to as many other places that you can think of. Like alternator, block, main ECU ground, main dash panel ground, headlight grounds & on & on. Use more of the copper AS compound on the wire to bus bar connections.

Sounds like a massive case of OCD, no? I submit to you that once you have done the overkill grounding thing to one car you will do it again to the rest of your rides. Of course there is no guaranty that this will solve your fog light issues. But you for sure be able to take the ground system off your checklist.

Also check out your fuse holder. Is it a spring loaded style like shown in the diagram? If so, the spring should be preloaded nice and tight when you put it together. Sometimes folks will use the short tubular fuse in an inline style fuse holder that was designed for a long fuse and there will not be enough contact pressure to make a solid connection. Then heat will build up at the fuse ends and the fuse will blow. What makes me think that this might be the case is that your fuse is blowing after a 1-10 seconds. Usually an overloaded fuse will blow instantaneously when the power is applied. Of course any other type of fuse holder will do the same if there is excessive resistance in it's connections. You are not using slow-blow fuses are you?

Back in the day, when I fixed motorcycles for a living, Honda used a lame inline fuse holder that did not use spring pressure at the ends like an inline spring type fuse holder. Honda was using an inline fuse holder that had simple u-shaped contacts that wrapped around the metal ends of the tubular fuse. Those funky fuse holders would often blow the fuses at the ends, a sure sign of poor contact. I soldered in a lot of the spring style fuse holders in those bikes.

[marlinh]

You may have faulty lamps. I would temporarily connect other lamps (a headlamp perhaps) that have the same draw into the circuit and see if your fuse still blows. Run a temporary ground to the battery. What is the guage of the wiring you are using to these lights. If it is too small that could blow fuses too. Too much resistance. The wiring to the relay and switches should be a smaller guage than the main wiring going to the lights.

[dlb]

from what you guys are saying, i'm thinking the ground wires should be a heavier gauge. it looks like the lights were installed as part of a kit but the ground wires are quite small, maybe 18 gauge or so. i'll try thicker stuff run directly to the battery and see how that works.

when i first got the car, the one working lamp lit fine and i replaced the other broken one with a new lamp so i think they should be fine. if messing with the grounds doesn't improve the situation i'll try some other ones like you suggest, marlin.

[4wdchico]

Check my previous post again, I added more stuff that may be of use.

[marlinh]

The circuit feeding the lights, both the positive and negative should be a larger guage. Not just the ground. The thin wire running to the lights will heat up and blow the fuse. Increased resistance = heat. That can create a fire hazard. That is the purpose of the relay, to prevent that extra current draw from passing through the switch and eventually burning the contacts. It also allows you to run smaller wires behind the dash, etc. I think 10 or 12 guage should be safe for fog lights. What size were the wires that came on the back of the lamps? Was something smaller spliced into them? Some of these kits are pretty lame. How are the wires spliced into each other? Butt connectors, solder and splice or those cheap blue clips that everyone uses and a few years down the road you can't figure out why your light don't work.

[Petros]

All good suggestions, but I would also check basics first. with a volt/olm meter check the power flow in and out of each item. It is possible you are drawing the power for the head lights from the switch on the dash (power coming through the fuse box). Just make sure the lights are drawing power from the correct contact on the relay. Check the resistance of the lights, the relay, switch, etc.

[teranfirbt]

Just to make sure, the fuse that is blowing is the one that supplies the lights (relay pin 30), not the switch? That can make a big difference in your hunt...

All things being equal, you can wire fog/driving lights with 55 watt bulbs from the relay with quality 16 gauge without any trouble, no reason for bigger... Assuming you're using a relay with 2 #87 pins. If you're paranoid, 14 gauge is the biggest I would go, anything bigger is a pain to work with.

If all of the wiring between the battery, the relay, and the lights is fresh and well done, then there is no reason for the fuse to be blowing, unless you have a fuse that is on the edge (a lower quality 10 amp fuse with 2 55 watts lights might do this).

[dlb]

finally licked this. i remembered that when i got the car, the driver side fog light worked fine even though the passenger side one was burnt out and had the wrong bulb. it only started blowing fuses after i replaced the passenger side bulb so i disconnected the passenger side and turned them on--driver side still worked fine, no blown fuse. so the problem was somewhere in the passenger side wiring. i found that someone had (poorly) spliced 6" of 18 gauge wire onto the end of the positive wire going to the light so that it could reach. cut it out and replaced it with matching 16 gauge (as that is what is used for everything but the hot wire to the relay) and it works! i knew it was going to be a stupid, easy solution. it was just a matter of finding it. thanks for all the suggestions and info, everyone.

i should mention that i really have no need for fog lights whatsoever. they're just one of those fun, neat gadgets and it bugged me to have them on this car but not functioning.