Automatic temperature/defogger wire

[MyTaurus8AChevy]

2004 Taurus with automatic temperature control.

Does anyone know what the color code is for the wire that goes to the rear defogger?

[shorod]

You have a few choices here. You have the wire (Dark Blue/Orange, pin 17 at the ICP) from the Integrated Control Panel (ICP) to the Generic Electronic Module (GEM). The GEM rides piggyback with the Central Junction Box (CJB) which contains the fuse for the rear window defogger as well as the relay for the rear window defogger. The relay provides illumination to the switch on the Dark Green/Violet wire (pin 7 of the ICP). The relay also provides power to the rear window defogger grid via the black wire (pin 18 of connector C270c at the CJB).

I should mention that this is per the 2002 Taurus factory service manual. I expect your 2004 will be very similar, but cannot guarantee that.

-Rod

[MyTaurus8AChevy]

Originally Posted by shorod

You have a few choices here. You have the wire (Dark Blue/Orange, pin 17 at the ICP) from the Integrated Control Panel (ICP) to the Generic Electronic Module (GEM). The GEM rides piggyback with the Central Junction Box (CJB) which contains the fuse for the rear window defogger as well as the relay for the rear window defogger. The relay provides illumination to the switch on the Dark Green/Violet wire (pin 7 of the ICP). The relay also provides power to the rear window defogger grid via the black wire (pin 18 of connector C270c at the CJB).

Any chance you can take a screenshot of that section? We're being told to rule out the black wire because it is too dangerous to use. I was told to use the dk. green/violet wire with a 1.2K resistor off of a relay to ground. If I could directly trip their relay it would be a lot easier and safer. Thanks.

[shorod]

Hmmm, your last post has me wondering what you are attempting to do. It doesn't sound like you're trying to make the rear defogger work, but rather to add something not originally on the car.

I could send you a PDF version of the diagram if you send me a private message with your request and an e-mail address that can accept attachments.

-Rod

[MyTaurus8AChevy]

Originally Posted by shorod

I could send you a PDF version of the diagram if you send me a private message with your request and an e-mail address that can accept attachments.

OK thanks Rod, I greatly appreciate it. PM sent

Our remote start has a special output that allows you to turn on the rear defogger while it's warming up the car. We'd like to add it but only if we can do it right. That's why I'm doing all of this research first

[shorod]

I sent the schematic just prior to reading this. Ignore my question pertaining to my curiosity.

You were told correctly, tapping into the black wire would not be the best choice. You should tap into the Dark Blue/Orange wire as that is the wire that the button switch uses to activate the timing circuit in the GEM which closes the relay. This activation would just require a momentary ground from the remote start system.

-Rod

[MyTaurus8AChevy]

Originally Posted by shorod

You should tap into the Dark Blue/Orange wire

Thanks again Rod for showing us this. We see now what Ford is doing to turn on the rear defogger.

Actually if we tap into the dark blue/orange wire it wouldn't do anything, because the switch is normally open and would block the signal from our remote. We basically need to recreate the whole integrated control panel section by tapping into the dark green/violet wire through a 1.2 K ohm resistor. See this diagram for how it will be hooked up. Adding this relay (which will be controled by channel 6 of our alarm system remote) it will send a 200ma negative pulse to our control relay. When the relay clicks on it will close Fords circuit, just as if someone was there pushing the rear defogger button. From the diagram it looks as if our heated mirrors will turn on also

[shorod]

Careful here, take a look at the factory diagram again. The DG/VT wire is on the switched side of the factory relay. All that wire does with the ICP is turn on the LED in the button, showing the defroster is on. Tying into this wire will not trip the factory relay since it is on the switched side of the relay rather than the coil side.

The GEM is what controls the factory defrost relay. When you momentarily press the button in the ICP, it grounds the DB/OG wire to the GEM. This activates the timing circuit in the GEM, and the GEM provides ground to one side of the factory defrost relay coil. When this happens, the factory relay closes, providing battery voltage to the black wire for the defrost grid and mirrors as well as the DG/VT wire which turns on the LED in the switch. The only purpose of the DG/VT wire is to turn on the LED in the switch, which is why there is a 1.2kohm resistor in series (to limit the current through the LED).

If you use Channel 6 of your alarm to provide a momentary ground to the DB/OG wire, you will not need to add an additional relay.

The DG/VT wire is tied to the black wire, which you mentioned earlier you did not want to tie in to.

-Rod

[MyTaurus8AChevy]

Originally Posted by shorod

Tying into this wire will not trip the factory relay since it is on the switched side of the relay rather than the coil side.

But aren't they both going to pin 7? This is pin 86 of the coil.

If you use Channel 6 of your alarm to provide a momentary ground to the DB/OG wire, you will not need to add an additional relay.

The second relay is to protect the alarm. If the channel 6 wire draws more than 200ma it will burn out the alarm. To guard against this a separate relay is used. If I knew how much the factory relay drew I probably could do without it, but I'd rather be safe than sorry

[MyTaurus8AChevy]

Wouldn't THIS also work?

[shorod]

Pin 7 of the ICP is a result of the rear defrost relay being closed, it has absolutely no control over the factory relay. The control of the relay is done by the coil. In the factory diagram, pin 85 of the relay coil is connected through fuse f2.32 to "hot in run." Pin 86 of the relay receives a ground pulse to activate by the GEM and only the GEM.

The GEM receives a momentary ground signal however long you press the button on the ICP to turn on the rear defroster. When you press the momentary button, the button shorts the DB/OG wire to ground G200. Ignore the 1.2kohm resistor and LED at this point. When the GEM receives a momentary ground on the DB/OG wire, it triggers a timing circuit. This timing circuit provides ground to pin 86 of the relay. While the GEM provides this ground, the relay closes and provides battery voltage to the black wire for the rear defrost and heated mirrors as well as to the DG/VT wire. Now that the DG/VT wire has power, it illuminates the "on" LED through the 1.2kohm current limiting resistor, completing the circuit to ground G200. As soon as the timing circuit times out and removes ground, the relay opens, the defrost turns off, and the LED goes out.

What you want to do is use Channel 6 of your alarm to provide a momentary ground to pin 6 of the GEM. This will activate the timing circuit of the GEM which will in turn close the factory rear defrost relay, allowing current to flow to pin 87 of the relay powering the defrost grid, heated mirrors, and lighting the "Rear Defrost" switch in the ICP.

I'll modify the factory wiring diagram and send it to your e-mail address so you can visualize this.

As far as using a relay to protect the alarm system, if it was properly engineering, the 200mA limitation is due to current limiting for the transistor that provides the ground to self-protect it. It will not attempt to provide more current that that. Since this ground pulse will only be used to activate a solid state timer in the GEM, it should not draw anywhere close to 200mA. However, if it makes you feel better, go ahead and use the relay.

-Rod

[MyTaurus8AChevy]

Originally Posted by shorod

What you want to do is use Channel 6 of your alarm to provide a momentary ground to pin 6 of the GEM.

Wouldn't it be easier to just ground the dark blue and orange wire since it goes directly to pin 6? Wouldn't that be essentially the same thing as grounding the factory switch to G200?

Since this ground pulse will only be used to activate a solid state timer in the GEM, it should not draw anywhere close to 200mA.

They (directed electronics) must suggest to use a relay because most people wouldn't be going through a solid state timer or a factory relay. I can see your point though about a second relay being overkill and I will try going directly to the dark blue and orange wire without a relay.

[shorod]

Originally Posted by MyTaurus8AChevy

Wouldn't it be easier to just ground the dark blue and orange wire since it goes directly to pin 6? Wouldn't that be essentially the same thing as grounding the factory switch to G200?

That's what the diagram I emailed you does. The factory switch is already grounding pin 6 to G200 when the "Rear Defrost" button on the ICP is pressed. The factory button is a momentary switch, normally open. One end of the switch is grounded at G200. The other end is connected to pin 6 of the GEM. When you press the button, pin 6 is shorted to ground G200.

The diagram I emailed shows how to ground the DB/OG wire using the Channel 6 output of your alarm. If you provide a momentary ground to the DB/OG wire, you are doing exactly the same thing as if you were to press the "Rear Defrost" button, and hence the rear defrost and heated mirrors will work from Channel 6 just like they would if you pressed the "Rear Defrost" button on the ICP.

-Rod

[MyTaurus8AChevy]

I finished this tonight. THANKS again Rod for all of your help! Not only can I turn it on remotely, but I can also turn it off