KJamesJR

I had a bad resistor, which was replaced. I now have heat and fan control settings back. However I turned the rear defrost on this morning (frost), and left it for ten minutes. Doesn't seem to be working. Any suggestions?

gpeade

I would check for current on the back glass first.

kjc

I have the testing/repair proceedure for a '93 GC.. I don't know what year/model you have

KJamesJR

I have a 98 XJ. I'm not seeing any nicks or breaks in the little metal lines running across the window. I also don't have a volt meter. Thinking maybe fuse or relay?

kjc

I'd think you could rig up a little test light for that.. a couple wires on a 12v bulb. The bulb would show either 12 (bright) or @6 (dim). That's about all the voltmeter was used for in the testing proceedure. 12v at the connector, 6v drop from connector to each metal line. But I think all you really need to check is if 12 v is at the connector, cause the testing indicated if there was a break in the lines somewhere, it'd most likely work in the other lines. (I assume there are several circuits (in parallel) so if one breaks, the others continue. Sounds like you're on the right track with fuse/relay.

Cherryokee

I lost the center high mount brake light on my '99 due to a broken wire to the tailgate. When I went in to perform the wire repair I found more compromised wires including the defroster wires ready to break, short-out and/or burn. In retrospect, the damage is/was the product of years of cable flex from the many gate lift cycles in its lifetime.



When testing for 12V at the defroster terminals (you should check one terminal to ground at a time and, then again, across both terminals) with ignition and rear defrost switched on, test for 12V with the tailgate closed (down obviously), open (fully up) and while moving it throughout the tailgate range of motion. Also, with the gate fully open you will see two flex boots in the hinge area, grab at the left one and manipulate it as best you can (squeeze, flex, push/pull and gurk it around). If there is any indication of 12V while manipulating the flex boot - or while at any position within the range of tailgate motion then a wire is broken inside the flex boot between the gate and the body. You may also want to check that center high mount brake lamp during this procedure - of course you'll need to peg down your brake pedal for that.



I'm assuming that you are not well-practiced at doing this kind of repair work. You'll want the repair to be done in a reliable and water tight fashion. If you find any evidence of broken wires when you perform the above procedure then I'll recommend you obtain the assistance of someone who is well-practiced at this kind of repair. On a scale of 1 to 10, I'll rate the level of difficulty for this task at "7".

KJamesJR

Thanks for in input. I'll go check it out.

weebur

Good advice from Cherryokee. I went through this last week. When pulled the boot down every wire in the bundle had cracked insulation, exposing the wires. In the process of fishing a pair of new wires through the boot I broke another. PITA job, but everything is working back there now. Do as I always do: solder the connections with silver bearing solder and use shrinkwrap.

Squelchtone

Just got my Jeep a week ago and this morning I wanted to use the rear glass defroster, the switch turns orange as if is going to work, but the glass elements never melt anything. rear wiper works, and pressing the button all the way makes it spray washer fluid and wipe, but no dice on the defroster. The rubber boots from the body to the tailgate are both split open, but without taking them fully off, I cant see anything obvious that is broken.

Will have to test with a volt meter this week, don't want to take all the boots apart if it is something like a fuse or relay, but would the orange light on the switch turn on if it couldn't complete the loop?

Thank you,

Squelchtone
2001 Cherokee Limited

CCKen

Do you see the defogger on light ON in the Rear Window Defogger Switch?

When you were troubleshooting the HVAC Blower control issue did you disturb the aux switch panel (Defogger Switch)?

Check fuses 12 and 14 in the Junction Block. If they are okay, swap the Rear Window Defogger Relay with the Cigar Lighter Relay and see if the defogger works.

gpeade

Heck I have continuity from one terminal to the other across the glass as well as power to it but mine won't heat the window.

CCKen

Here's some rear window defogger diagnostics:

Squelchtone

Thank you CCKen, I will try these instructions this week!

Sweet Tony

Where did you get THOSE pages from? That is the book I want!

boxburn

Head over to cruiser54.com and download the FSM for your year. I had to go through the files and rename them for ease of use.