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Remote Start Runs Rear Defog, 99 Silverado - FYI

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Forum Name: Car Security and Convenience - Hot Topics
Forum Discription: Stickied topics from our Car Security and Convenience forum. Car Security and Convenience FAQs. Read First!
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=19042
Printed Date: March 28, 2024 at 11:50 PM


Topic: Remote Start Runs Rear Defog, 99 Silverado - FYI

Posted By: captntech
Subject: Remote Start Runs Rear Defog, 99 Silverado - FYI
Date Posted: September 19, 2003 at 10:34 AM

This works on a 99 Silverado or probably any non-databus rear defog.

I've figured out a way to run the rear defog/heated mirrors using the trunk pop button on a remote starter (Crimestopper RS-900 in my case). There is a white wire coming from the HVAC module that is a ground trigger from a timer inside the HVAC module. You can tap into this ground trigger wire (goes to a relay under the hood to activate the defog circuit). I purchased a timer relay circuit board made by Elk (Model 960 Timer) and got it for $28 shipped from Bass Home Products:

https://www.bass-home.com/ProductDetail.cfm?cfid=391008&cftoken=46415239&ProdID=88018

Installation: connect the +12v to constant power (it automatically runs a timer cycle when you put power to it so you don't want it on keyed power). Connect ground to GND and strap a wire from GND to COM(mon). Connect a wire from NO to the white wire coming from the HVAC. Set the timer to 10 sec until you have applied power, let it run a timed event, then change the jumper to min. Connect your remote trunk pop trigger wire to the TRIG on the timer. I also added an amber status light on the dash to indicate that the timer was on. I used a 12v LED in amber housing from Radio Shack and connected the positive to keyed +12v and the negative to the NO on the timer. Pressing the trunk pop activates the trigger which activates the timer which activates the defog circuit and turns on the status light. After the timed event ends, the circuit opens and shuts down. Do not run the defog without the engine running, you'll run down the battery. Good Luck.







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