i had an issue with my 99 Ram last month where the fog lights would work but the headlights would not. I replaced the switch and all was well - all lights worked. I tried using the fog lights last night and they would not come on. The switch illuminates indicating that the fog lights are on, but no lights. low and high beam on headlight works fine.

Does anyone have a wiring diagram they can send me for a 99 Ram QC that could help me troubleshoot? I don't know what wire to test at the switch to determine if power is going to the fog lights. Is there a way test for power to the lamps? Both bulbs are fine. I swapped the relay in the PDC with another and still no fog lights. I checked the fuse in the cab and still no go. Is there a easy way to jumper power to the relay socket in the PDC to see if the fog lights work and verify that the wiring from the PDC is good?

I know this is a popular topic but I coudn't find what I was looking for as far as a wiring diagram goes and I think I've tried all suggest solutions except buying another switch.

thanks

- Dan M

 

Did you buy a completely new switch, or a used one from a salvage yard?

 

It is a new switch from a local dealer.

- Dan M

 

you could try this, it's for an 01 but alot of us use it....
https://dodgeforum.com/m_340929/tm.htm


good luck

 

Wiring diagram. Without DRL. (daytime running lights)

 

Thanks for the link and diagram. The link was helpful, it had some fog light troubleshooting procedures. The diagram was nice, showed wire colors and paths.

I *think* I found the problem. The troubleshooting procedures pointed toward an issue between the fog lights and fuse in the PDC. Also, I could hear the relay activating (I stated in my original post, I swapped it with a known good relay). Since the relay was working, that told me that the wiring between the fog/head light switch and the multifunction switch is working properly (fogs should only come on with low beams). In checking out the wiring, I found what appears to be a broken wire under the truck near where the fogs connect into a larger bundle of wires. The wire was bent and appears broken but the coating is still intact. Before I could finishing testing with my multimeter, the battery died and I didn't have a spare. I ran out of day light before I could fully check out the wire and splice it.

I will keep you all updated. Thanks for the assistance.

- Dan M

 

Best Gift - I ever received!!!

And have put it to good use a lot lately..

 

good to see you making some progress at least

 

merry christmas from DF! lol

 

I think I have (had) 2 issues going on.

I fixed the wire break. Now I get voltage to all 4 wires at the fog lights themselves (pulled bulbs and probed). I also probed the connectors inside the PDC at relay spot 30 and saw steady voltage (constant voltage always on regardless of key/switches).

This tells me that the upper left section of the wiring diagram is good. This includes both fuses, both fog lamps and the fog lamp indicator on the switch in cab.

I also probed relay spot 86 inside the PDC and it had steady voltage (like 30, constant voltage regardless of key/switches). This tells me that the multifunction switch on the steering column is good (also a new switch). This clears everything above the fog lamp relay in the wiring diagram.

This leaves the headlamp switch itself (lower left on the wiring diagram) which wires to relay positions 87 and 85. I saw no voltage there when the fog lights were turned on at the headlamp switch in cab (which has the fog light indicator turned illuminated).

This leads me to believe my headlamp switch in cab is bad. As I've stated before, the relay is good, I've swapped it with known good relay (ASD) and all is good.

However, based on the troubleshooting procedures in the service manual link provided the reason for fog lamps being inoperative and the fog lamp indicator is illuminated is either

1. the fog lamp fuse defective (solution to trace short circuit and replace fuse) or
2. open circuit from fog lamp fuse to fog lamp (solution check wiring circuit from fog lamp fuse to fog lamp. trace open circuit in wiring and repair).


I don't think either of these 2 solutions apply as i get steady 12v to both wires at both fog lamps.

electrical wiring and systems are definately a weak point for me. From my understanding when the head lamp switch is set for fogs on and the low beams are on, it energizes the relay to make 87a connect to 87, complete the circuit which would turn on the fog lights.


Does anyone have any thoughts on this?

- Dan M