troubleshooting rear defrost

hello, my rear defrost does not work. last time it did work it worked perfectly. i push the switch/button, the orange light comes on, you hear a click like your supposed to, and the yellow light shuts off after about 10 minutes like its supposed to, like it always has, but the window does not get defrosted, any suggestions?

If no power at window I`d look for wiring corrosion/breaks behind the kick panel by your left foot ,as well as wires running front to back under door frame trim( the proper terminology escapes me right now ...lol) Drivers side.

well theres no power at the window, ill try to take a look at the wires in the next few days

well i checked last night and did not see 1 single thing wrong. i started down by my left foot and followed it all the way back to the defroster. the only place i didnt look is behind the dash.

would it work if i just ran 2 wires back there myself and connected them to a toggle switch? i understand i'd have to be sure to shut it off in a certain amount of time. if that would work would it work plugging it into my cigarette lighter? or would it most likely blow that fuse?

and since i still cant edit my posts, a problem thats been pissing me off for months now, ONLY on this website, i wanted to add if all of that would work, which side is positive and which side is negative, or does that even matter?

bump, anyone?

i'm having a problem with the site too myself, but its mostly with posting anything. I have to hit the go advanced button to get anything to post for me.

My rear defroster dosn't work in my sunfire either. I've just been too lazy to really care and figure it out. Hasn't worked from day one at the dealershit... Told em I wanted it fixed and it wasn't.

I have the same symptoms too bud.

check the output volts at the back of the HVAC unit to make sure its not the unit itself before you tear everything apart, and you didn't have power at the driver side connection or passenger side?

and you didn't have power at the driver side connection or passenger side?

im not too sure on that one actually, with the voltmeter i put the negative prong on one side of the window and the positive prong on the other side of the window, i did not try the positive prong on both sides while grounding the negative prong on the body

Positive lead is on the driver side, the prong on the passenger side is strickly ground.

those cars are known for the prong that that defrost plugs onto to break on the drivers side about half way down the window if not then you may have a break in the graph thats on the window which is sorta easy to test once you push the button and you have the voltmeter one on the left side and one on the right it should read near 12 volts. also check the plug behind the button to assure its connected.

i'm having same problem with my 99 cavalier rear defrost. Passenger side is neg/ground and driver side is positive. With your meter put the positive side on the driverside wire, disconnected from the window, and your negative wire grounded to metal, I used the door hinge plate. I am getting power, unfortunately it's only 2 volts, unlike my book says i should be getting 6 volts. I'm guessing at the moments it's the switch and I think the dealer said a new switch is $259.

i'm having same problem with my 99 cavalier rear defrost. Passenger side is neg/ground and driver side is positive. With your meter put the positive side on the driverside wire, disconnected from the window, and your negative wire grounded to metal, I used the door hinge plate. I am getting power, unfortunately it's only 2 volts, unlike my book says i should be getting 6 volts. I'm guessing at the moments it's the switch and I think the dealer said a new switch is $259.

Get one from e-bay. Its the whole HVAC unit itself.

I just fought through the same issue...defrost light works for the prescribed 10-15 minutes then shuts off, no power to the rear window.

I removed everything I could to get to the wires from end to end. I found that there is a thick purple wire coming from the controller (switch end) and a black wire going to the grid on the rear glass. The two wires meet at a cheesy plastic connector just above/behind the left kick panel -- by the drivers left foot. I separated the connector and found that the metal connectors within were heavily corroded and the plastic slightly burned.

A quick cleaning of the connector was all it took to get the rear defrost working as advertised.

I suspect that I will create a more permanent connection for the larger guage wires (Purple in / Black out) that is separate from the other wires in the connector. I checked another Cavalier a few minutes ago and it had the same problem for over two years...quick fix this time.

Good Luck.

Yeah I just found the same thing before I came back to read any updates, I have a burnt connector. Too bad for me I bought that whole HVAC unit. At least i got it off ebay for 40 bucks instead from the dealer for 259. Thanks for taking the time to add to the forum.

I am going through this same problem with my daughter's car, everything seems to work fine but no voltage at rear glass, if I pull one of the leads from the rear glass my twelve volts comes back. Could this be a problem in the glass itself?

If your getting 12 volts then evreything is good up to that point. It's sounds like you might have a bad connection to the glass, or maybe a bad ground. The positive side is on the drivers side, and the ground was on the passenger side on my car. I would also check for any bad breaks in the lines. If you put your negative wire to somewhere else on the car for a good ground and get voltage when touching the line then it's probably your ground on the window. I hope that get's you in the right direction.

Thanks for the info. I tried this morning, same outcome. Here is what I have tried so far, disconnect both leads at rear glass get twelve volst lead to lead, connect the positive lead at left side and check voltage from right side tab on glass to negative lead get twelve volts, connect negative lead to right side tab and check voltage between leads and no voltage when leads are connected. I've ohmed out the window wires from tab to tab and show no breaks. Even ran a separate ground wire to car frame, as soon as I connected it to the window I lost voltage. Any suggestions?

If you have power when checking an open circuit but not when it's connected to ground, it's probably a very high resistance in the wire or relay. Connect one lead of your voltmeter to the positive side of the window grid and the other lead to as far forward in the circuit as you can. If you read anything over .1V, keep moving your test leads closer and closer together until you maintain that reading and can't go any closer. That will be your high resistance. DO NOT check the circuit with an ohmmeter, it probably won't show your problem, you need to check with the circuit live.

Hey guys, search for the thread on here for rear defogger!.. I had just fixed mine today because of the green wiring harness that connects the power to the rear defrost, ( defogger) You'll find a ton of info on that thread. So helpful I cant stand it!.. Mine now works like a dream.. here's the link..
http://www.automotivehelper.com/topic750208.htm (http://www.automotivehelper.com/topic750208.htm) Good luck.. i have some infor on there too, check stevePT's thread and Mmy thread.. i put as much info as i could, cuz i have no idea bout wiring and things like that.. Its most likely the wiring harness..

I dont know if its against the rules of the site,but if somebody could take a cellphone pic or something,of the connector by the kickplate for me,that i keep reading about, i would appreciate it.I looked under the kickplate on the drivers side,and theres about 4 or 5 of them. Which one is it. Thanks!!!

I dont know if its against the rules of the site,but if somebody could take a cellphone pic or something,of the connector by the kickplate for me,that i keep reading about, i would appreciate it.I looked under the kickplate on the drivers side,and theres about 4 or 5 of them. Which one is it. Thanks!!!

The connector (for me anyways) was litterally right behind the carpet on the driver side close to the door, it's lightish-green and about the size of 2 flash-usb drives put together. It has a couple wires going into and out of it, the biggest being your power wire, purple going in and black (i believe) coming out. If this connector is your problem, you'll see it almost immediately, cause the wires on mine were corroded and the plastic was burnt-black. What I did was splice a piece of wire connecting the two wires together around the connector, worked like a charm!

But, that being true, the darned thing died again. I have no clue what could be happening this time...anybody have any ideas before I run out and buy a multi-meter/volt-meter?