defrost in 2000 grand prix

OK I've been searching the forums for a while. I'm trying to locate the rear defrost wire on my 2000 Grand Prix. From what I've found it should be a white wire hooked up to a relay. I can't seem to find it under the driver side dash or steering column. Does anyone know where the wire is? Also, once I find it, am I going to need another relay when wiring to my car alarm? I have a Python 872 that will automatically turn the defrost on when the car is remote started.

It's at the switch.

Are you sure? Is it coming off the wires running out of the back of the HVAC? I tried pressing the button and listening for the relay to click and I thought I heard it over on the passenger side somewhere.

There is a switch to turn the rear defrost on manually. That is the switch he is referring to. It may be mounted in the panel with the A/C controls. You are not going to need another relay if you find the wire that controls the factory relay.

well thats what I figured he was saying but im not going into the HVAC unit itself. There are plenty of wires running out the back of the unit but I'm not sure which one runs the defrost. How would I test them to find out?

Have you removed the panel with the switch mounted to it, to see if you can follow the wires or traces from the switch to the plug? There should be only 4 or 5 wires going to the switch. If you can find those wires, we should be able to help you.

As the idiot stated..... pull the panal and look at the plugs on the back. The wire you are needing is there!

well i took the HVAC unit out and there are about 20 wires coming off the back of it. So I used my multimeter and tested some wires. One of the white wires tested at like 0.3 volts when idle and 12v when i pressed the rear def button so I assumed this is the wire I need. I spliced into it and hooked it up to the remote start but when I hit the button for it the interior lights flash on and off about four times. Nothing happens to the rear def. Any ideas as to what is happening?

ok the signal u got on the white wire is 12 positive, the signal from ur alarm will be negative, yo'll have to use a relay like this. wire pins  30 annd 86 to a constant 12 volts, pin 85 to the defrost wire from the alarm, and hook pin 87 to the wire on the defrost switch. hope it helps.installin's easy. its da customers who make it hard.

ok i wired up a relay like you said but i get the same result. Also when I wired in the relay the defrost switch does not work at all. Before the relay the switch still worked when pressed manually.