I have a 2000 XJ 4.9L 4x4, the heater worked fine yesterday and this morning when I started her up the heater nor the A/C would not kick on. There was no air coming through the vents at all (yes I turned the component ON lol). I have checked the fuses under the hood and on the passenger side and none of them are blown. I'm not super savvy with electrical anything and this morning was 21deg. Any and all help would be greatly appreciated thank you!

 

Does the heater work on High? (In other words, if you turn everything on and set the fan speed to the highest setting).

If it works on high and only high, then you have a problem with the blower motor resistor. If the heater does NOT work on high, you need to unplug the blower motor and check that you're getting power at the connector.

The 97+ seems to have a lot of issues with the blower motor wires melting around the resistor (due to a worn out blower motor drawing too much power), so that's the first thing I'd be looking at.

 

Okay I'll check the blower and see if that's the problem! Thank you for the help!

 

Keep us posted please!

It should be easy enough to tell if the blower works on high - just turn the heat on normally and set the fan speed to the max setting and see if it kicks on.

The blower motor itself (where the connector to test is) is accessible from the outside of the Jeep by removing the panel between the hood and the windshield and the blower motor resistor (where the wire melt is common) is accessible from inside the Jeep, passenger side under the dash. I believe that you can pull the plug on the blower motor without having to take the motor out... you can always jump the blower motor to the battery to see if it kicks on when you've got the connector pulled (if you're careful - the little alligator clips and some electrical tape to keep from "crossing the streams" will make that sort of test easy.)