Cherokee XJ '98 - Fog Lamp Relay...?

[DinoJeep]

Hi,

 

My Cherokee XJ restoration has hit a small electrical hurdle!  I decided to replace the old front fog lamps (the rectangular ones set into the front spoiler) and have realised that the switch isn't working!  I can't find the relay on the standard fusebox/relay panel in the engine compartment, and tracing those wires with the radiator in isn't so easy...  Can anyone please tell me where the front fog lamp relay is located, I'm pretty sure it's this that needs replacing, as the fuse appears ok.  

 

Thanks,

Dave.

[V]

Neither of my XJs have front fog lamps so I don't know where the relay is located.

 

However, the fog lamp switch itself can go bad. If you cannot find a new replacement, they can be restored internally using solder to thicken the worn contact area. This video shows a restoration without the solder, then with.

 

If your switch is OK and you cannot find the relay, you could just wire in a new relay and abandon the original in situ wherever it is.

• the orange wire and the black wire into the switch are for illumination.
• the purple wire is power in, not sure which fuse yet.
• the blue wire is switched power out

[DinoJeep]

Hi V- good to hear from you again.  The switch is easy enough to get to, so it won't take long to check it - good idea though, I'd assumed it was the relay, but the switch won't have been used for years.  Lord knows why Jeep decided to stuff the relay somewhere dark and isolated in the engine bay - I've got a pair of round spots on the bull-bar that were added by the previous owner, one of the kits with its own relay and a 30amp fuse - easy to find!  

[V]

Good news for locating the relay! I just checked my FSM and the relay is in the Power Distribution Center (The big fuse box next to the battery).

 

The black wire in the switch is the ground for illumination.

 

The fuse is a 10A, No.7 in the junction block

[V]

Look in the PDC lid for the diagram showing the relay position.

[V]

If after testing the relay it is found to be bad and you cannot locate a new replacement, message me on here.

[DinoJeep]

Hi V - aha! You got the same as me, this is where it gets interesting as the car came with the 2 fogs installed and wired, but the relay in the PDC is where things get hairy - see the photo (sorry, sunlight obscured a bit), above "A/C Clutch" is the fog-lamp relay, but this is the REAR fog lamp!  It works ok.  Then above that is FOG (DRL Only), now I don't know what DRL means, but I wondered if it was something to do with the front fogs, and as it was empty I tried the rear-relay, but there's no connections under the plastic guides, so obviously this is a dead/spare relay socket.  From what I read online it seems the relay for the front fogs isn't in the PDC at all, but in the engine bay somewhere - so the mystery continues.

 

PS - I am still going to check the switch though - the relay may not be the issue, wherever it is!

Edited July 18, 2022 by DinoJeep
add photo

[V]

Interesting.

 

The circuit diagrams show that the same switch is used for front and rear fog lamps. Fog lamp relay 1 and 2 are in the PDC, the second one is for territorial legal restrictions on using with high beam only(?). The diesel wiring diagram shows that the rear fog lamp relay has a logic gate inside it, so I don't think this is the one in the PDC. I have yet to find the location. At a guess, it may be on the instrument cluster panel.

 

The circuit diagram shows both the fog lamp and headlamp switches providing switched power to a diode module. The diode module provides power to the rear fog lamp relay (with logic gate) which provides power to the rear fog lamps.

 

DRL is Daylight Running Lamps

[DinoJeep]

Vince - thanks very much for the latest info.  I'm not that proficient in reading wiring diagrams and I'd missed both F/R foglamps going through the same relay.  So this implies that if the rear-fogs work, the relay is good, and as the rears are on a different switch, it may well be that the green front switch is the root cause here - I'll get the blighter out and have a look inside... I'll let you know what happens.

 

PS. Thanks for the DRL translation - it was driving me mad trying to work that one out!!

[DinoJeep]

It was the switch!  I removed it, then took it apart, cleaned all the contacts.  It's still a bit jittery and only one of the lamps works at the moment, so some more contact cleaning to go, but on the right path.

 

Thanks very much - that was timely advice!

Cheers,

Dave.

[V]

I am glad it worked.

Your switch is fine now if one of the lamps works.

There is a splice in the light blue wire upstream of the lamps, that means that lamp on the branch either has a bad earth on the black wire from the lamp or there is a conductivity problem on the light blue between the faulty lamp and the splice.

Edited July 18, 2022 by V

[DinoJeep]

I gave the switch another overhaul and it's a lot more steady now - I think it'll improve with use.  Thanks for the extra info on the black/blue wires, I'll start at the connection with the lamp and work back - hopefully track it down at some point.

 

Thanks again for your help Vince, if I get to one of the meets (Aldermaston/Kielder) this year, and you're there I owe you a beer.

Dave.