D3 rear heated windscreen issue?

[Architex_mA8tey]

Ive noticed on my D3 that the rear heated windscreen works fine but when I have pressed the button it only seems to be on for a minute or two before auto switching itself off again, so I end up going through pressing it then watching the button for the light going off then re-pressing which is a pain.

Surely it should be on for longer than 2 minutes and if so why would it be cutting off sooner?

[mattylondon]

Come to mention it mine goes off quickly, although I've not timed how long. I'll look into it.

[mattylondon]

Rear window heater control

The convenience system central control unit activates the external rear window heating relay -J9 (relay coil). The information to activate the heated rear window is transmitted via CAN from the air conditioner operating and display unit. The air conditioner operating and display unit is the master unit in the heated rear window function and can, if necessary, initiate cyclic operation of the rear window heating via CAN. During starting actuation of the rear window heater is interrupted.

I'll carry on digging...

[Architex_mA8tey]

Originally Posted by mattylondon

Rear window heater control

The convenience system central control unit activates the external rear window heating relay -J9 (relay coil). The information to activate the heated rear window is transmitted via CAN from the air conditioner operating and display unit. The air conditioner operating and display unit is the master unit in the heated rear window function and can, if necessary, initiate cyclic operation of the rear window heating via CAN. During starting actuation of the rear window heater is interrupted.

I'll carry on digging...

Cheers Matt not sure what they mean by "If necessary" lol

[mattylondon]

Actuation of heated rear window at temperatures below 0 °C stays on with no time limit until shut off at temperatures above 0 °C it is shut off after approx. 10 min.

Above 0 °C the rear heated screen is controlled by a complex algorithm of outside ambient temp, internal temp and humidity, and energy management.

[mattylondon]

Originally Posted by Architex_mA8tey

Cheers Matt not sure what they mean by "If necessary" lol

Indeed. A simple, timed 5 minute, on off would have been better. Over engineering at its finest to reduce the electrical load to save a teaspoon of fuel a year.

[Architex_mA8tey]

Originally Posted by mattylondon

Actuation of heated rear window at temperatures below 0 °C stays on with no time limit until shut off at temperatures above 0 °C it is shut off after approx. 10 min.

Above 0 °C the rear heated screen is controlled by a complex algorithm of outside ambient temp, internal temp and humidity, and energy management.

So if mine is staying on only for 2 minutes or so then which component isn't functioning correctly and are there any tests on VAGcom to confirm this?

[mattylondon]

Originally Posted by Architex_mA8tey

So if mine is staying on only for 2 minutes or so then which component isn't functioning correctly and are there any tests on VAGcom to confirm this?

Ah... I've found more.... There is different coding for different engines and glass. Maybe yours is controlled to be time-limited between 2-20 mins

- Coding for vehicles with 8-cyl. engine and heat insulating glass.

- Actuation of heated rear window stays on even at temperatures below 0 °C but time-limited (depending on ambient temperature between 2 and 20 min).

[Architex_mA8tey]

Originally Posted by mattylondon

Ah... I've found more.... There is different coding for different engines and glass. Maybe yours is controlled to be time-limited between 2-20 mins

- Coding for vehicles with 8-cyl. engine and heat insulating glass.

- Actuation of heated rear window stays on even at temperatures below 0 °C but time-limited (depending on ambient temperature between 2 and 20 min).

mine is a V8 petrol 4.2 but i wasn't aware that it has heat insulating glass, I'll check that out now, god they don't make it easy do they. . .

**UPDATE** yep there it is on my option list 4GP - Heat Insulating Glass LOL

[mattylondon]

You should be able to recode it to stay on for 10mins, as per standard glass.

This site gives a break down of the coding for the Air Con.

http://www.audi-portal.com/en/diagnostic/ecu_10602.html

Ross tech web site has nothing.