So I've got a 1990 4.0, 5 speed. I've been doing a lot of camping lately and ending up out in the woods long after dark, finding the headlights to be grossly inadequate. So what have done its ordered a 50 inch light bar and a couple of pods to light things up a little bit.



I wanted the main light bar on its own switch, and the pods on their own switch. I also wanted a quick and easy way to later on easily add more things, such as a winch, and on board air. That being the case, I snagged an old fuse box out of a Cherokee at the junkyard. With the drawbacks to the stock alternator I decided to go with an auxiliary battery setup as well, with an isolator, to run my electrical components without having to worry about killing the battery miles out of town.



So this is my personal little wiring diagram I came up with. As you can see all of the electrical components run off of the auxiliary side the isolator. The power for the switch comes directly from the auxiliary post on the isolator, it's then chassis grounded, with a lead then going back to the fuse box to a relay to provide power for the lights.




The switch I'm using.





NAPA part number for the switch





My isolator setup. Rear post is aux side. Leftward is the alternator input. Forward post is starting battery.

So the problem I'm having is that I'm finding I have power to the switch but it's not opening the relay when the switch is thrown. I can manually jump the relay to fire up the lights, so I know that works, but I'm thinking I screwed up somehow with the pin-out on the relay somehow.




Chrysler relay from the cherokee fuse box



The beast.

What I'm hoping is that one of you guys can spot my screw up. Any help is appreciated. Thanks!

 

Check the coil of the relay using an meter set to ohms, depending on the one you have if it reads OL (digital) the coil is open and won't work.

 

Have you thought about doing the headlight harness upgrade, I did it and was very pleased with the results.

 

You're right on cliffy.......

 

Before you bought a light bar and pods, you should have upgraded your headlights and wiring first. Those two upgrades by themselves are worth the money.

 

This. https://www.cherokeeforum.com/f67/headlights-203245/

 

Did you check all the wiring between the switch and the relay? If you have power at the switch but not at the relay, it has to be something in between those two. Check power out of the switch, and then check at the relay too to see if its getting current. I really doubt it's anything to do with the relay since you can manually jump it. Those things really don't require much current to power up the coil.

 

Also if the relay has a diode in the input circuit you may have it hooked up backwards, try swapping the two wires on the input circuit.

 

Thanks, in the process I also deleted that crusty corroded plug underneath the air filter box.

 

Also agreed. If you like doing wiring stuff, a headlight harness is pretty simple to build and it will have a massive improvement over stock.

Relays are always diodes. Sending current through a relay in reverse switches the polarity on the coil and the circuit won't close.