Golf 5 auxiliary heater/climate control not activating

Hello,
I installed a TT-V control unit via CAN in a Golf 5 TDI. Everything works perfectly except that the Climatronic is not being controlled. The auxiliary heater also starts when I press the instant heating button, but the LED for the instant heating button does not light up. I have done this conversion several times before, and so far it has always been successful . Could it be that the auxiliary heater is too old and I need a separate IPCU module (in that case, at least the LED for the instant heating button should light up)? Or can I reflash the STH or install different software to fix the problem?

Best regards, Peder.

Hi,
You mentioned that you've done this conversion several times before: Could you possibly provide me with a wiring diagram for the harness? I installed a trailer hitch from a Golf V into my Golf VI Variant yesterday and I'm currently wiring it up.

Sure, I'd be happy to help! Please provide the text you would like me to translate from German to English.

I already replaced the Climatronic unit with one that has an instant heat button. It's also working fine, even though it's from a Passat. The 'instant heat' button doesn't work, though, because the auxiliary heater isn't connected yet.

Do I need the relay in the wiring harness? Actually, doesn't everything go through the CAN bus?

For your information: The mounting brackets for the Golf V also fit the Golf VI. You only need the special windshield washer fluid tank designed for auxiliary heaters, with a capacity of 3.5 liters.

Best regards,
Stefan.