I need help with the freaking headlights on my grand Cherokee. they will not come on , I've done the switch and checked fuses, all of them are fine. what is up...

 

You replaced the switch. The headlights switch?

Did you test anything yet? I think the best thing would be to use a DVOM or illuminating test lamp to test and see if there is power getting to the headlights switch. Also, test for power leaving the headlights switch. See if there is power getting to and out of the switch.. You could check for power at the headlamps too, if/when you see normal power coming out of the headlights switch. This should lead you to the problem area.

It is likely to be a problem located where the wiring exits the firewall going to the connector that connects to the wiring harness. Or, it is likely to be a problem with the wiring behind the headlight where it comes back leading to the wiring harness near the airbox.

It is possible for this issue to be caused by a fuse or maybe the daytime/delay headlamps module? You checked the fuses already.. I would focus on testing for power at the headlights switch first though, since this will basically eliminate the possibility of it being the result of a blown fuse, or a problem at the module.

 

I know the WJ has relays. Does the ZJ?

 

All vehicles have relays for high current circuits.

 

Wrong! The XJ pulls all the current for the headlights thru the switch! This is the whole reason for the headlight upgrade harnesses being sold.

 

Ooops. You are correct. Same on my 84 Chevy pickup.

Okay, all MODERN vehicles have relays for high current circuits!

 

Nothing I uncover mentions anything about headlamps relay in a ZJ. The wiring goes from the harness in the engine compartment all the way to the light switch and then back to the lights.

The headlamps switch is overloaded new from the factory. It also has a super weak earth link to it, with too much tied into it. It is also located in a bad spot making it worse.