99 concorde rear defog remote start

I'm going to be installing a CS-2014 remote start / alarm by Crimestopper in my 1999 Chrysler Concorde LXI next week and am curious about how to interface with the rear defogger / defroster. I have 3 or 4 AUX channels on that unit that I could use but since I have the Automatic Temperature Control (ATC) I'm not sure how I should go about it.

The way I see it I have only a couple of options --

One -- Open up the ATC unit and solder wires to the physical switch and use an Aux line to power a relay to make momentary contact with the two wires (exactly mimicking a button push).

Or Two -- On the other side of the body control module (BCM) use a relay to ground the rear defogger relay while the remote start is engaged / aux option is on.

I don't like the idea of opening up the ATC but if I use option two I would assume there would be no indication that the rear defogger was actually on (via the light on the ATC panel). If I do open the ATC I assume it would function as if I pushed the button with my finger, light would come on and defogger would be on it's 8 minute (or whatever it is) timer and shut off automatically.

Does anyone else have any other suggestions?? I bought an iDataLink module, unfortunately it doesn't appear the current firmware will control the rear defogger, which is too bad, my first experience with the add-on data modules and they have a ton of potential but without the firmware support for some older vehicles.

Thanks in advance for any insight.

Tom

Find the trigger relay in the right side of the trunk. Find a dk.blue/white on that relay. send a negative trigger to this wire..

It should be a latched trigger.... so test to verify.

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Can I assume that this will bypass the BCM and ATC completely? I am okay with this but I will just have no indication of whether or not the defrost is on. I also lose the timer function, which maybe is a good thing -- if there is no problem leaving the rear defog on for 20+ minutes.

Do I need to diode isolate or can I just 'T' into this relay wire?

Thanks,
Tom

Ok, so I T'ed into the ground side of the coil for the relay that enables the rear defrost. This appears to work fine but I have an issue, the power side of the coil is a constant 12V (not switched with ignition). I haven't checked to see if the 12V supply to the defrost grid is switched or not (one would assume it is) but the question is -- on the CS-2014 I can set that aux to be timed up to aprox. 5 minutes, is there any type of circuit I could build / buy that would give me 10 - 20 minutes or maybe a way to switch it off once the key is put in the ignition.

Thanks,
Tom

You could use the GWR to operate the defroster.

I picked up another relay and I think using a GWR is what I'm going to do. Instead of using a aux channel I'm going to install a small spst switch so the defrost always comes on during remote start when the switch is in "winter mode" and doesn't when it's in "summer mode". The aux channels on this are nice to have but for stuff like a rear defrost it would be nice if there was some indication on the pager remote or the interior LED that they were activated. Anyway, thanks for your help on this guys the install went really well, just a few more tweaks to finish up.

Great job! I've used the summer/winter switch to operate the climate controls, as well. It's a biatch or impossible, depending on the type of factory controls.

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