Hey all, i think i might have discovered an issue that is causing my rear defroster to malfunction. It is the electric grid type and it hasn't worked since I've owned the car. I bought a NOS correct relay since the original was pretty rusty and rough looking. I also replaced the 30 amp inline fuse for it. Even after replacing those, it still wasn't working.

Today I was poking around in the trunk and found a big black ground wire that was taped up at the end and not connected to anything, looks like it runs up to the rear window. Could this be the ground for it?

 

Its been years since I messed with one of these. Back to the top to see if someone else can help.

John

 

I realize this thread is a few months old, but I am still having issues with the defroster. I replaced the defogger relay, the 30 amp inline fuse, and connected what I believe is the ground wire that wasn't connected in the trunk. I also replaced the A/C relay that the defogger relay connects to.

I got the hi speed on my fan working now so I have a better idea what is going on. When I turn the hi speed on, then turn on the defroster, the fan kicks down to speed 3, which I know is normal. The red light on the dash next to the defroster switch is also on.

But now when the defroster is on, the Gen light on the dash comes on and stays lit. It only stays dimly light, hard to notice when it is during the daytime, but easier at night. So I can't really tell if it is working or not. Should I be able to feel any heat or anything from the glass? What is the best way to test it?

 

use a volt meter and ground the black lead to a good ground and gently touch the red lead to the lines going across the glass to check for voltage . some of the lines may have a open part way across the line. Check at both ends of the line for voltage, if only on one side you have a break somewhere in that line. I have heard of repair kits for those but have never used one myself.

 

I know this is for a Chevy but if you scroll down there is a schematic specifically for a rear window defroster, I'm thinking it's the same or similar as an Olds.

http://www.peachstatechevelles.com/docs.ashx?id=47572