Fog light wiring issue

Vehicle: 1998 Cherokee Sport. Factory Fog lamps.

The original Fog lamps were a corroded mess. There wasn't even enough metal left inside to hold the bulbs. So I installed some aftermarket ones and spliced on the factory plugs. No worky

I flip the switch inside on the dash. Light does not light (may be bad).
There is one Fog Light relay in the PDC under the hood. When the lows are on, the relay is energized. When the high beams are on, the relay releases. There is 12V on one side of the switched output, and nothing on the other. If I jumper that connection, nothing happens.

I then went to the fog light side and tried to find continuity to ground, and I didn't find one. I also flipped the lights on and turned on the fog switch, no 12V at the lamp plug.

I only have a 2000 schematic, and I looked for connections past the PDC. I found C106, which it describes as being on the engine bay front left. Of course the airbox is in the way... Is that the only connection between the PDC and the relay?

Anything I may have missed?

Ron

Zuki-Ron said:

Vehicle: 1998 Cherokee Sport. Factory Fog lamps.....I flip the switch inside on the dash. Light does not light (may be bad).

Click to expand...

The fog lamp switches are not very robust and any increase in resistance (corroded lamps) will usually burn them out.

There is an unmarked fog lamp fuse in the PDC, make sure you check them all. If the fuses are good, suspect the switch is toasted.

Tim_MN said:

The fog lamp switches are not very robust and any increase in resistance (corroded lamps) will usually burn them out.

There is an unmarked fog lamp fuse in the PDC, make sure you check them all. If the fuses are good, suspect the switch is toasted.

Click to expand...

Hmmm.

On the control side, the switch runs a (fused) relay, which uses the low beams as it's power source for the coil.
On the output side, it has a fused source of power, the relay contacts, and the fog lamps.

The control side works, the relay engages. The output side power source fuse is OK, there is constant power to the relay. There is no ground or power on the lamp side. Is the only connector the one on the front left fender? Or is there another connector somewhere?

Ron

If you have 12v power out of the fog lamp relay with the factory switch engaged, run some fresh wires from near there. My fog lamp wires were green with corrosion 6" back from the fog lamps.

Damn, am I stupid!

Thanks for the info Tim, you were right on the money with the Fog Lamp Switch!

I put the disk aside and got out my Haynes manual and started over.

I couldn't find a ground at the lamps because the bumper and mounts were corroded, so I went to the battery - OK ground though wiring

Then I looked for voltage at the lamps - None

I went back to my relay, thought about your post, and tried it without the FLS on, but headlights on low - The relay still engaged. <scoobie sound>

Well, when all else fails :rtm: so I did just that, again.

The circuit comes from the battery, then though the relay, which it uses for logic. Then to the FLS, then straight to the lamps :banghead:

So 100% of the current drawn by the fog lamps goes though the FLS, you know, just the way they tell you never to wire auxillary lights :gee:
I removed the switch, it's a melted mess, so I jumped the contacts and the lamps work!

Lesson learned. Thanks Tim!

Ron

Yep! My fog light switch gets warm when I have my fogs on for a while (I'm running 100 watt H4 bulbs off it... probably should not... have been too lazy to put in relay boxes so far, even though it's like a 1 hour project). The factory fog light wiring is on the same harness as the rest of the front lights, the connector is a rectangular one between the ECU and the airbox, if you reach one arm down on each side you can usually wrangle it loose after some cursing and struggling.

Sounds like your factory fogs were in the same condition my right hand one was in - I always wondered why my left light was a blueish tinged and my right light was yellowish... till I got in a fender bender. Had to take a sawzall to the bumper on the right end to get at the bracket bolts again, looked down right afterwards and saw a pile of rust flakes on the ground right under my right fog light. When I finally got the fog light off the bumper and opened it up, there wasn't any reflector left, just a bulb suspended in midair.