Rear defroster doesnt work?

[my85grandnation]

I discovered during the last freeze that the rear defroster in my 85 T-Type doesnt work. When we first got the car I believe that it did work but I am not certain since one of my GN's also has rear defrost so I cant remember if the T-Types worked as well or if Im just remembering the GN's working. We havent done anything to the car since we got it except put in a new engine. I dont think that would cause the defroster to not work but am not sure. The button when pushed clicks like it tries to come on but it doesnt light up and the window will not defrost. Could it be a bad or dirty switch? Let me know what I should check out on the car. Thanks

Dusty

 

[XLR8]

I had a switch go out on me once about 10 years ago. If it's not lighting up, it may be the culprit. You should be able to remove it, and using a multi-meter check to see if it works.
I also had a defroster go out when the grid matrial on the rear window was damaged. If that is the case, you can buy a repiar kit for it at any auto store.

 

[Turbo Brian]

One of the bus bars on the defroster grid supplies power and the other supplies a path to ground.

Ground a voltmeter ground wire on the door striker and put the power lead on the bus bar to see if voltage is present at the bus bar. (I forget which side is power, but you can check the working vehicle to figure that out)

Usually it is not the switch that is the culprit, but the connection from the bus bar to power or ground. I have found the braided cable to ground broken on one vehicle and the power supply connection broken several inches from the bus bar on another. Good Hunting!

 

[ANDYS87]

It could also be the relay

 

[DMan]

Where is this relay?

I have the same problem, however my switch lights up.

 

[got rice?]

my blazer had a broken wire before,but opening and closing the hatch im sure caused that.but just for the hell of it,check the wire at the glass.

 

[my85grandnation]

Thanks for your help guys I got it figured out. It turned out just being the switch. I took the one that I knew was working and plugged it in and it came right on. Now I just have to find a new switch. Any of you guys know where I can get one. I want to get a NOS one thats in great shape because whichever car it goes in are both 40k mile show cars so I dont want a used one.

 

[ANDYS87]

The relay is under the dash. I never checked the location in my GN but in my 80's Monte Carlo, its plugged into the fuse box.

As far as buying a new switch, I'd try PostonBuick. If not there keep an eye on Ebay.