Rear Defrost?
Moderate User
Joined: Oct 2008
Posts: 17,003
Likes: 21
From: Albany, NY
Easier Relay breakdown http://www.the12volt.com/relays/relays.asp
Relays with 5 pins(87a) are the same as 4pin relays except they can be wired to accomodate for additional switched circuits. For ex. having your Accessory Foglights turn off when highbeams are switched on.
Standard on/off operation with a switch, a 4pin relay is suitable. A 5pin relay can be used and you would just ignore the center pin(#87a).
Last edited by dirtydog; Dec 6, 2012 at 07:41 AM.
Champion
Joined: Aug 2006
Posts: 4,489
Likes: 4
From: New Jersey
I dont see why you would connect both 85 and 86 to ground??? It's one or the other. Most cheap relays you can switch pins and it doesnt make a difference which one goes to ground. Others have a diode to protect against backfeed current when power is switched which would force you to put 86 to ground, and the other pin(85) would go to switched voltage source such as a switch. The voltage difference bewteen the two legs is what energizes the coil. The voltage difference creates a certain amount of Current which is automatically controlled by the relay through it's internal resistor(60-75Ohms). Otherwise, you'll never have a change in voltage if both pins are to ground. Any other wiring method is not correct and sounds like your not even using the relay but bypassing it. There are several ways to wire up a relay, but if you keep the coils energized and/or use main line in as a switch(pin 30) you are going to ruin the relay with arc'ing.
Ridiculous Relay breakdown http://www.bcae1.com/relays.htm
Easier Relay breakdown http://www.the12volt.com/relays/relays.asp
Relays with 5 pins(87a) are the same as 4pin relays except they can be wired to accomodate for additional switched circuits. For ex. having your Accessory Foglights turn off when highbeams are switched on.
Standard on/off operation with a switch, a 4pin relay is suitable. A 5pin relay can be used and you would just ignore the center pin(#87a).
Ridiculous Relay breakdown http://www.bcae1.com/relays.htm
Easier Relay breakdown http://www.the12volt.com/relays/relays.asp
Relays with 5 pins(87a) are the same as 4pin relays except they can be wired to accomodate for additional switched circuits. For ex. having your Accessory Foglights turn off when highbeams are switched on.
Standard on/off operation with a switch, a 4pin relay is suitable. A 5pin relay can be used and you would just ignore the center pin(#87a).
lol I mistyped meant to say run power through 85 & 86 to ground.
trust me I know my relays... Been doing wiring for a pretty long time.
Banned
Joined: Nov 2005
Posts: 3,739
Likes: 8
From: MD
Just bought a 06 Ram 1500 4.7 Megacab. It has heated mirrors and rear defrost. The problem I have is that the rear defrost doesn't work because the wires that are suppose to be attached are gone. Please, does anyone know where they are suppose to be coming out of the rear panels at, so that I know where to start looking. I don't want to just start tearing it apart if I can help it. Thank you for any information you can provide.
Moderate User
Joined: Oct 2008
Posts: 17,003
Likes: 21
From: Albany, NY
You have a Quadcab. 2009+ they started calling them Crewcabs. Nothing like tryin to confuse people. I think they went to Crew's because thats what every other manufacturer calls them.
Thread Starter
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Amateur
Joined: Jan 2011
Posts: 31
Likes: 0
From: Forsyth, Ga
Sorry, maybe I missed something. But I still don't know if I have to plug the relay into anything? I'm gonna get all the supplies I need to do this today. Hopefully after I figure out the relay issue I'll have it up and running tonight.
Thread Starter
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Amateur
Joined: Jan 2011
Posts: 31
Likes: 0
From: Forsyth, Ga
I know you did. And I appreciate it. But I don't know what to do with the relay. Does it plug into the fuse box? If so, then how do you attach the wires.
