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Discussion Starter #1
First, I want thank everyone that contributes to this site because it has helped me immensely and saved me TONS of money.

Ok, I have 2005 Taurus SE with manual, cloth seats. I bought a complete set of charcoal leather seats out of a 2004 Sable that I am going to swap in. Since I live in Michigan, I figured I would take the opportunity and install some aftermarket seat heaters before I put them in the car. I bought two ComfortZone Universal seat heaters and installed them into the seats with no issues. The seats are now ready for installation into the car.

My problem is not with the mechanical installation, but with the electrics. Routing the wires and mounting the switches is easy enough, but how best to power them? Each seat will draw about 7.5 amps and I would prefer that they be on an ignition circuit so that I don't have to remember to switch them off.

I have looked a just splicing into an existing circuit, but which one? I have also looked using an "Add-a-Circuit", but that seems kind of a hack solution. I asked a buddy who does a lot with car audio and he suggested using a relay, but I don't know how that would be controlled off of the ignition.

Any suggestions?

Thanks.

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Use a relay. One set of terminals on the relay will power the magnet which will complete the circuit of the other set or terminals. Tap a wire to the ignition (or the radio since it's on the accessory circuit) and use that as the switch to power the magnet. The other set of terminals is a direct connection from the battery to the relay and then from the relay to the seat warmer.
 

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There is a wire (thick, orange/blue) in the bundle that runs under the kick plates that I used for my reverse light, courtesy light mod... It is only hot in ACC or RUN... New source from the battery and a relay is the best way to go.
 

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:withstupid:

Mike
B)
 

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Discussion Starter #5
Ok, so I bought a 30amp relay. The part number is LD1A-12F and it has a really small diagram on it and some instructions on the back. Here is what it says:

30H - terminal for horn/lights
87B - Terminal from power source
86S - Terminal from switch
85M - Terminal for relay ground wire

So, I want to make sure that I wire it correctly and I don't understand what the 86S "switch" is. I think that this is a 12v line in from an ignition controlled circuit that activates the relay. And, I assume that 87B is power directly from the battery, 85M is just a ground and 30H is the output from the relay that will actually power the seat heater.

Can someone who has wired a relay or two maybe confirm this for me?

Thanks in advance.
 

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Ok, so I bought a 30amp relay. The part number is LD1A-12F and it has a really small diagram on it and some instructions on the back. Here is what it says:

30H - terminal for horn/lights
87B - Terminal from power source
86S - Terminal from switch
85M - Terminal for relay ground wire

So, I want to make sure that I wire it correctly and I don't understand what the 86S "switch" is. I think that this is a 12v line in from an ignition controlled circuit that activates the relay. And, I assume that 87B is power directly from the battery, 85M is just a ground and 30H is the output from the relay that will actually power the seat heater.

Can someone who has wired a relay or two maybe confirm this for me?

Thanks in advance.
[/b]
Once you figure out relays they are really idiot proof and you'll be wanting to use them all the time!

86 will be the orange/blue wire I told you about that is the hot in RUN/ACC. This is called the "trigger" for reference sake... Then 85 is the ground for "trigger" wire... If there is no where for the current from the trigger to flow, nothing will happen so that is why it has to be grounded! Think of it as a "draw bridge" that closes...

Now, about the other two terminals... Is this a 5 terminal relay or only 4 terminal? Either way, I'll asume 87 is a "normally open" terminal and that 30 is the "switched wire" that will actually carry the power to the seat warmers. 87 will be where you attach your 12v source from the battery (with an inline fuse remember). "Normally open" means that when the relay is not active, the litte "draw bridge" that opens and closes to allow the current through is normally open (makes sense right?). In a circuit "open" means that the little "draw bridge" is open so the current can't flow through. When the relay is "activated" by the "trigger" (remember the ignition wire), the little "draw bridge" closes and allows the current to flow over it... Once this is achieved the power will flow your the 12v source on 87, down through the relay to 30 where it goes to your seats. So long as the ignition is in RUN or ACC you will be able to turn your warmers on and off as you wish. When the ignition is off, the "draw bridge" opens again and the power supply is shut off...

Hopefully this explaination wasn't too patronizing for you!
 

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Discussion Starter #7
Hopefully this explaination wasn't too patronizing for you!
[/quote]


Nope, that is exactly what I was looking for. I did some reading on relays before I posted and everything I read lines up perfectly with your explanation. My issue was that the "standard" relay diagrams all used the Bosch numbering scheme on the pins and they didn't quite jive with the numbers on my relay. That, and when you are dealing with 30 amps, it is probably better to be 100% clear than to FRY something, right?

Yes, on the inline fuse. I read on several posts/blogs that a relay is not fused and that I should wire it with an inline fuse as close to the battery as possible. Just for safety purposes, I am also going to wire each seater with its own inline 7.5 amp fuse. It is probably overkill, but for $5, who can argue?

So, my wiring diagram will be 12V from the battery, with an inline fuse, to Terminal 87B. I tap into the orange/blue ignition fired wire and run that to Terminal 86S. Terminal 85S will be grounded to the body and Terminal 30H will be wired to the "red" wire coming from the seat heaters.

This is a 4 terminal relay.

Yeah, the more I read about them, the more I like them. My issue was with the "trigger" power source. I was thinking of a relay in terms of a switch and it didn't make sense to have two hot leads coming into it. Once I read up on it, along with your description, it makes the picture crystal clear! No more $30, 20 amp switches for me!!!

Thanks again, guys! I will post some pictures after I finish up.
 

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Hopefully this explaination wasn't too patronizing for you!

Nope, that is exactly what I was looking for. I did some reading on relays before I posted and everything I read lines up perfectly with your explanation. My issue was that the "standard" relay diagrams all used the Bosch numbering scheme on the pins and they didn't quite jive with the numbers on my relay. That, and when you are dealing with 30 amps, it is probably better to be 100% clear than to FRY something, right?

Yes, on the inline fuse. I read on several posts/blogs that a relay is not fused and that I should wire it with an inline fuse as close to the battery as possible. Just for safety purposes, I am also going to wire each seater with its own inline 7.5 amp fuse. It is probably overkill, but for $5, who can argue?

So, my wiring diagram will be 12V from the battery, with an inline fuse, to Terminal 87B. I tap into the orange/blue ignition fired wire and run that to Terminal 86S. Terminal 85S will be grounded to the body and Terminal 30H will be wired to the "red" wire coming from the seat heaters.

This is a 4 terminal relay.

Yeah, the more I read about them, the more I like them. My issue was with the "trigger" power source. I was thinking of a relay in terms of a switch and it didn't make sense to have two hot leads coming into it. Once I read up on it, along with your description, it makes the picture crystal clear! No more $30, 20 amp switches for me!!!

Thanks again, guys! I will post some pictures after I finish up.
[/quote]

Remember too that 5 terminal relays are very useful for doing the opposite... The 5th terminal is the "normally closed" terminal, so it works backwards... Whatever you have the "trigger" hooked up to will turn off the supply power... I wanted to power something when the ignition wasn't in RUN/ACC for a mod I did and I used the "normally closed" terminal for that...
 

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I would not tap into any existing wiring for a 30A load. You should run a new wire for that large of a circuit. Easiest place to tap into always hot power is the post on the MEGA fuse.
 

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Discussion Starter #11
I would not tap into any existing wiring for a 30A load. You should run a new wire for that large of a circuit. Easiest place to tap into always hot power is the post on the MEGA fuse.
[/b]

That is what I am planning to do. I will only tap into an existing wire for the relay "trigger" which is only a few milliamps.
 

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I would not tap into any existing wiring for a 30A load. You should run a new wire for that large of a circuit. Easiest place to tap into always hot power is the post on the MEGA fuse.
[/b]
What's the MEGA fuse?
 

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<div class='quotemain'>
I would not tap into any existing wiring for a 30A load. You should run a new wire for that large of a circuit. Easiest place to tap into always hot power is the post on the MEGA fuse.
[/b]

That is what I am planning to do. I will only tap into an existing wire for the relay "trigger" which is only a few milliamps.
[/b][/quote]


Well the trigger is going to be what? A thermostatic switch or a on/off switch?

Either needs power whenever so it can use the same source for feed or switched power.
 

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Discussion Starter #16
<div class='quotemain'>
<div class='quotemain'>
I would not tap into any existing wiring for a 30A load. You should run a new wire for that large of a circuit. Easiest place to tap into always hot power is the post on the MEGA fuse.
[/b]

That is what I am planning to do. I will only tap into an existing wire for the relay "trigger" which is only a few milliamps.
[/b][/quote]


Well the trigger is going to be what? A thermostatic switch or a on/off switch?

Either needs power whenever so it can use the same source for feed or switched power.
[/b][/quote]


I am not sure I understand your question. The "trigger" is going to be power from an ignition fired circuit, i.e. a circuit that has power only when the ignition is ON. This will energize the coil in the relay. So, basically, the ignition will be the trigger.
 

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Yeah...I wouldn't go that route unless you want to boil your "little boys". Remember, heat is bad for your reproductive organs, and I can see that getting old in the summer.

If I were you, I'd wire up a switch in between the power feed and the trigger, or in between the relay and the seat feeds. Then you'll be able to turn the heated seats off when you want to.

JR
 

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In his original post he mentions that wiring the switches is easy enough but that he wants it to be on an ignition circuit in case he forgets to turn them off...
 
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