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relay help, will this work?

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=21156
Printed Date: July 12, 2025 at 3:14 PM


Topic: relay help, will this work?

Posted By: rye2
Subject: relay help, will this work?
Date Posted: November 08, 2003 at 10:40 AM

hi,

I wanted to wire up my rear defogger to turn on when I remote start my car. I don't have nay extra AUX channels on my remote starter, so I was told that it could be done by using my bypass module's power wire as a trigger and then running a relay that will switch on the rear defogger. One draw back that was explained to me is that with this hook up, every time I remote start my car the rear defogger would turn on, which wasn't a big deal. I don't use the remote starter at all in the warmer months....I live in a cold climate in winter so I thought that having that rear defogger running for say 10 mins or so before I head out there to brush the snow off will be a beneficial thing.

Here's my question....about the relay wiring...
I'm wondering if this will work...

87 to rear defogger on rear window.
85 to chassis ground
30 & 86 to Bypass module power wire

My knowledge of relays is a little amateurish, I'm learning though!

Any other things i might be missing?

I thing the run time of my rear defogger is abut 15 minutes...

Car :2000 cavalier...is that helps...

Thanks...



Replies:

Posted By: sroth140
Date Posted: November 10, 2003 at 3:05 PM

on the cavalier the purple wire on the climate control panel sees 12v +.  the only thing is (this is stright from DEI) if you dont run the output from the RS timed at 30 sec, you could burn out the switch.  it may also be possible to run a 12 lead to the actual relay that the switch operates.  i haven dug into my 98 cavalier yet to hook it up but i called DEi at work and thats what they told me.  i happen to have several outputs to use on my alarm/rs unit, the channel i plan on using can be programmed to output for up to 90sec by using the bitwriter.

i would avoid using the bypass wiring however, its best to leave that alone.  id use a wire off the RS relay control ribbon.  run an additional relay from there.  id go 30 output, 87 12 volts, 85 trigger 12 volts from RS ribbon, and ground 86, and 87a cap off.





Posted By: rye2
Date Posted: November 10, 2003 at 6:58 PM
So u are saying my best bet is to tap off a line from my remote start and use a relay that'll run directly to teh rear of the car.....?

IS that a safe way? would that cause too much strain on the tapped wire?   I don't want things to burn up...

maybe explain yourself a little clearer,





Posted By: sroth140
Date Posted: November 10, 2003 at 11:12 PM

uhhh "tapping" into a RS wire is the same as using your vehicles actual ignition wire.  thats what its for, supplying 12v when the ignition is on.  and i dont think the relay for the defogger is in the rear, im pretty sure its towards the front, probably under the hood.

i did a defogger output with an avital RS in a nissan quest.  i called dei and they told me what wire to tap into and the factory timer would take care of the rest.  with a cavalier its different, it wont work quite the same because of its unique wiring.  i cant tell you what to do and dei wasnt very clear for me.






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