Direct wire rear defrost

Good morning,

No, that would be a bad idea. The rear defogger is on a timed circuit. The antennae is a constant circuit. This means you can overheat the rear window and run the risk of fracturing the glass from too much heat.

Did you check the fuse for the rear defogger?

Make sure the fuses to the HVAC system in the fuse panel have power on both sides with the key on. The control head for the AC module controls the activation of the rear defroster and also controls the time based on ambient temperature.

Roy

The heater and A/C programmer receives the rear defogger request from the heater and A/C control assembly. The heater and A/C programmer will then send a Class 2 message to the body control module (SBM). The SBM will control the rear defogger on/off status and the amount of time that the rear defogger is on. The SBM will communicate the rear defogger status to the heater and A/C programmer over the Class 2 serial data and the heater and A/C programmer will light the rear defogger indicator accordingly.

Okay, let me know.

Roy

Did you reply? I see you posted but nothing came up?

Roy

No worries. Wanted to be sure I did not miss something

Roy

I attached the diagram for you to view. Check the 40 amp fuse.

Roy

Yep, test for power on both sides with either a test light or voltmeter.

Roy

Sure, let me attach a guide for you.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Roy

Voltmeter and multi-meter are the same things.

Roy

You are welcome.

Always glad to help.

Roy