Rear Defog Wire

I have a Viper 791xv in my 98 Jimmy, installed it myself last year but didn't hook up the rear defogger because I couldn't find any info on how to. With winter coming again, I'm wondering if anyone knows where I can find the rear defrost control wire?

I have a Viper 791xv in my 98 Jimmy, installed it myself last year but didn't hook up the rear defogger because I couldn't find any info on how to. With winter coming again, I'm wondering if anyone knows where I can find the rear defrost control wire?

If its behind the dash, just pull the switch and see, ground is always black.

Hehe. Yeah. I seemed to recall it was a sealed unit last time I had the dash apart, but I'll see what I can figure out and post back. You'd think someone would have this info though... the chilton's book doesn't even have it in the wiring diagrams.

Hehe. Yeah. I seemed to recall it was a sealed unit last time I had the dash apart, but I'll see what I can figure out and post back. You'd think someone would have this info though... the chilton's book doesn't even have it in the wiring diagrams.
They like to keep little things from us I think it is a deal they have with the auto manufactures.

So I finally got around to looking at this today as daylight was fading. On 98 Blazer/Jimmy/Bravada the back of the manual A/C unit has a 4 wire plug that controls the rear defog. Unfortunately, it's controlled by an IC. Theoretically you could bypass this by sending latched +12 down the wire that doesn't read +12 with the lights on or black. Maybe add a diode for safety sake. However, this is probably the better option:
http://www.the12volt.com/installbay/forum_posts.asp?TID=82602&get=last