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Upgrades (non TDI Engine related) The place of handling, lighting and other upgrades that do not relate to the performance or economy of the TDI engine. In other words upgrades to your TDI that don't fit into TDI Fuel Economy & TDI Engine Enhancements.Please note the Performance Disclaimer

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Old December 7th, 2017, 16:43   #1
Veteran Member
Join Date: Jul 2008
Location: Sachse, Texas
Default Rear defrost wiring question

I just finished installing a remote start on my 2002 jetta wagon TDI.

There is an optional wire for rear defrost activation.

This wire supplies - 200mA (ground) and can be set to on, latching, or pulsed.

Is the rear defroster is something that is triggered by a low amperage signal, or is it entirely controlled by the switch in the dash?

If there is a trigger wire can anyone let me know wire color and location?

I found T23/16 black/brown at the CCM in bently which shows to be a rear window defrost circuit but it doesn't seem to do anything.

Is my only option to run a dedicated wire to the defroster switch and power it with a relay?

I know I can install a relay and send a full power but I was just wondering if there is a wire I could tap into to activate the rear defroster?

Any help is greatly appreciated.

BTW I know some of the members here don't agree with remote starters, for the most part they don't live in northern Minnesota. Another reason I installed it is to have the car start and run for 15 minutes every 2 hours. This can come in handy if the car is parked outside over night or when I am ice fishing for any extended period of time. One extra bonus is the range of the remote is a verified 1200 feet (works for locking and unlocking doors also).

Last edited by kbrenny; December 7th, 2017 at 16:49. Reason: addition
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Old December 11th, 2017, 11:18   #2
Veteran Member
Join Date: Jul 2008
Location: Sachse, Texas

After reviewing the diagrams in Bently this is what I discovered:

T7/6 white at the defroster switch is the 12v+ output to the defroster element
T23/16 Black/brown is the 12v+ trigger that causes the CCM to energize the heated mirrors. (totally seperate from Defrost circuit factory)

I ran a spdt relay:
12v- signal from the remote start to pin 85
pin 86 and pin 30 to fused 12v+ at 30A under dash
pin 87 to t7/6 white at defrost switch

I also ran a second wire from pin 87 with a diode to pin T23/16 black / brown allowing the relay to energize t23/16 but not allowing t23/16 to energize 87 at the spdt relay.

This setup will turn on the rear window defroster and heated mirrors when the remote start unit sends a 12v- signal to the spdt relay.

In addition, under normal driving or operating conditions the rear defroster now also activates the heated mirrors.

There is no relay in the rear defroster circuit, the switch does everything.
on the switch T7/1 is 12v+ for switch illumination when parking lights are on
T7/2 is ground for illumination and indicator lamp
t7/5 is 12v+ input to switch
t7/6 is 12v+ output to defroster element.
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