Rear window defroster doesn't work in 1996 Lumina

[cubsfan24]

Another problem now that it is cold and snowing here in Indiana. My rear window defroster doesn't work. The rear defrost light does not turn on at all. I looked at the fuse and it looked fine. The first time I tried to use it a couple weeks ago it did not work. I went back to the connectors on the rear window and wiggled them around and the next time I started the car the light came on and I turned it off because I was just testing to see if it worked. Then a week later I tried to usethe defrost again and it didn't work. I didn't have time to fuss with it so I left it alone. Now that is snowing and getting iced over a lot, I would like to try to fix it. I tried playing with the wires again and I can't get it to work. I was thinking it could be the switch but I don't know how to test it.

[Andrew]

use a DMM at the wires at the window to make sure you are getting current there.

[cubsfan24]

What do I put the leads of the multimeter onto? Also when do I test this, when I am pushing the button?

[rockfangd]

well if the light is not lighting up i would say power is not traveling to the rear window. I would say either timer, fuse, or commonly the HVAC knob switch goes bad

[cubsfan24]

Ok, so you have heard of those switches going bad? How do I go about testing the swtich? Also, were is this timer at? Sorry for all of the questions but I have little idea how a rear defroster works.

[GJD5]

the entire rear grid should be a continous circuit to ground. So using your multimeter on ohms setting, put one lead on each connector and the other on a good ground source somewhere else on the car. It should say "1". Showing a continous circuit.

 

Do that first. If that checks out, you don't have power going to the grid and I need to know if you have the pass/driver temp control (CJ3) or the single temp control(C60).

[rockfangd]

ok if you pull the hvac unit from the dash and test the wire that goes for the rear defrost for continuity when you push the button. I think both the gen 1 luminas and the gen 2 luminas suck for their hvac setups lol

[cubsfan24]

The other day I put one lead of my multimeter on the connector on one side of the window and the other lead on the connector on the other side of the window and it was a continuous circuit. I will try to connector to ground tomorrow when it is light out and hopefully not as cold. Also, I have a single temp control.

[GJD5]

Ya, check that ground first and post back.

 

Since you have the single temp control...your relay is built into the control unit. If your grid is continous to ground like it should be, you then have 3 fuses to check in the fuse panel on the passenger side(like the door jam area). #4(15amp), #15(15amp) and #16(30amp). If all 3 fuses are good, then use your multimeter to check voltage going to each fuse. Let me know if you need help with that.

[cubsfan24]

Ok got some more info. When I went into the car this morning I started it up and tried the defroster. It didn't work. As I came home after a half hour drive I tried the defroster just for kicks and giggles. I was amazed to see that it worked! I went and got my multimeter and tested for a continuous circuit between each side to ground and both of those were fine. I checked the voltage while the defroster was on (the car wasn't running though). The drivers side voltage was 3 or 4 volts I can't remember and the passenger side was 10.33 volts. I think the other time I had the defroster work this season was when the car was hot. I checked the fuses and all three of those are fine. After the car cools off I am going to check to see if the defroster still works.

 

Edit: went out to the car 5 hours later and the defroster still comes on. I had a little problem turning it off though. I had to really push the button hard for it to go off. Then I had to push it really hard for it to go on and off again. I am thinking the switch is a little picky and needs to be pushed harder. I will try it again tomorrow morning after it sits all night. I thought I was pressing the button hard enough but mabey not hard enough lol.

[GJD5]

The defroster knob/button should push easy. If I were you I'd start looking for another control unit at the j/y.

[cubsfan24]

Ya, there is a control unit ending on Ebay in a day and a half that I will probably bid on. The knob seems to only want to work when I don't need it to . Thanks for everyones advice.

[rockfangd]

lol i have had the same problem with my cutlass for a long time, but mine didnt have a problem with the button it just wouldnt shut off once you got it to come on lol. Mine sounds exactly the same as this though,

I replaced the timer unit under the dash to no avail as it still does the same exact thing