rear defrost dont work

[jking03]

okay today was the first time i ever touched the switch for the rear defrost since ive owned my 88 wag... the switch lights up.. but the window was still foged all day.. anyone got any ideas... is this a typical thing... also the switch to raise or lower the rear window does nothing.. can only open winow with the key at the tailgate..

[El_Diablo]

atleast yours lights up, haha.... ive got a lot of wiring to do...

yours should be simple, just track from the switch back, if you have any broken defrost lines it will cause the issue aswell

[vintagetrks]

use the side view mirrors.LOL I would start with the switch. Check to make sure it works someone will hopefully chime in with how to test it. then move on back from there also check all your fuses, remember start simple.

[El_Diablo]

use the side view mirrors.LOL I would start with the switch. Check to make sure it works someone will hopefully chime in with how to test it. then move on back from there also check all your fuses, remember start simple.those dont work either on mine, im screwed, lol :rolleyes:


decent lil write up-

http://www.ifsja.org/tech/electrical/defroster_repair.html

and a wiring diagram-
http://www.ifsja.org/tech/electrical/defoggerdiagram.html

[jking03]

ive checked the fuses was good but replaced anyway.. also looked at the breaker for the rear window it was also good... all the lines in the glass seem to be good didnt see any breaks... i was gonna take the panel off the tailgate and get in there with a test light or volt meter just wating for nicer weather.. working out doors..

did a tune up on the ol gal today just as it started snowing... was an intresting afternoon hands so cold i coulndt get cyl #6,8 wires back on had to come in and warm up first

[vintagetrks]

those dont work either on mine, im screwed, lol :rolleyes:


decent lil write up-

http://www.ifsja.org/tech/electrical/defroster_repair.html

and a wiring diagram-
http://www.ifsja.org/tech/electrical/defoggerdiagram.html

Your in a jeep why worry about whats behind you hehehe :thumbsup:

[jking03]

those dont work either on mine, im screwed, lol :rolleyes:


decent lil write up-

http://www.ifsja.org/tech/electrical/defroster_repair.html

and a wiring diagram-
http://www.ifsja.org/tech/electrical/defoggerdiagram.html

hey el.. my power side mirrors work awsome lmao :D

ill check that thread link there
thanx

[El_Diablo]

you suck :p

[jking03]

you suck :p


does your rear window go up and down with the switch on the dash???

[vintagetrks]

Did you test the defrost switch? Just cause it lights up does'nt mean it works. I've got the old manual side mirrors they always work LOL :D

[jking03]

other than the fuses i didnt check anything else yet.. i was more worried about the tune up she needed badly..... had hood up last night with engine running and sparks were everywhere from bad plug wires.. i was out side freezing my arse in the snow for about an hour or so.. she runs better tho...

just looking for some quick ideas

how ever when i hit the switch i did notice a small change on the voltage gauge... it droped a little but recoverd quickly...

[vintagetrks]

other than the fuses i didnt check anything else yet.. i was more worried about the tune up she needed badly..... had hood up last night with engine running and sparks were everywhere from bad plug wires.. i was out side freezing my arse in the snow for about an hour or so.. she runs better tho...

just looking for some quick ideas

how ever when i hit the switch i did notice a small change on the voltage gauge... it droped a little but recoverd quickly...

Gotta love the arcing plug wires at night. I would'nt think turning on the defroster would pull enough juice to make the amp guage jump. Could be as simple as a bad switch but it could be a gremlin in the back too. I would try cycling the switch a few time in hopes that it was just not making good contact. Then I'd test the switch.

[jking03]

okay if this dont show that i have nothing else better to do at nearly 1am... i just went out side and fired up the wag.. turned on the switch for the defrost tried to cycle it off and on but once i turned it on it wouldnt turn off??? only shutting down the engine turned off the defroster so its sitting out there running gonna check in a few mins if it turns itself off or if it melts any snow...
dont know if its boredum or dedication

[El_Diablo]

does your rear window go up and down with the switch on the dash???yup, lol, and thanks to you i was out freezing my arse off testing the fuse, lmao....


the things we do for these jeeps :rolleyes:

i just found my multimeter and im tempted to go back out :rolleyes:

[vintagetrks]

okay if this dont show that i have nothing else better to do at nearly 1am... i just went out side and fired up the wag.. turned on the switch for the defrost tried to cycle it off and on but once i turned it on it wouldnt turn off??? only shutting down the engine turned off the defroster so its sitting out there running gonna check in a few mins if it turns itself off or if it melts any snow...
dont know if its boredum or dedication

Sounds like a bad switch then. :cool:

[El_Diablo]

on mine, checked the fuse... it was good but the switch wont light up so i guess tomorrow i get to pull the switch and jump the connections to see if i get anything, according to that write up, if the light comes on then the issue is between the switch and defroster, if not then its the wiring before the switch....

[jking03]

well it didnt turn off by itslef and no snow melted either..

where can i get a new switch?? or do i need to go junk yard hunting

[710 Burner]

The wires break off the glass and have to be reattached.
Possible bad switch preventing turn off or the timer relay is getting stuck on.
I do not recall the 88 tailgate wiring, but on the earlier models the light was feedback from the timer relay, so if the light was on that meant the relay was engaged.

[FSJ Guy]

The dash switch simply sends a signal to a relay/timer device in the tailgate. THAT silver box then in turn sends electricity to the defogger grid.

When you try to turn it off, the dash switch sends another signal to the silver box telling it to turn off.

Since your light is lighting up, that seems to indicate that the silver box is working. With the motor turned off, key on, push the dash switch. When the light turns on, do you hear a faint click from the tailgate? If so, your silver box is working.

Now it's time to get dirty. Remove the tailgate carpet and the access panel.

You can do this with the tailgate closed, but it's easier with it open.

Depress the safety switch (driver's side) and CAREFULY raise the window. You'll have to support it as it comes out. Use an appropriately sized trashcan, box, spouse or beer-buddy to hold the window. You may have to put a heavy toolbox on the tailgate to keep it from trying to rise up on you.

Now you will see the silver box on the passenger side of the regulator assembly. There should be a large and small plug attached. The small plug should be a single wire. That goes to the passenger side of your defogger grid. The other side of your grid gets a wire going to ground.

Use a voltmeter to verify output when the defogger is turned on. I found that when not under load, the voltage pulses. I didn't check to see if it did this when hooked up, too.

As for not turning off, that could be a loose plug (the large one) on the silver relay box or in fact the dash switch is on its way out.