My series 4 turbo 2 now that it has an aftermarket ecu wired in, when the interior fan is turned off, the compressor runs whether the aircon switch is on or off. If the fan is on, I can turn the compressor on or off with the air con switch. Hence I need to start the car with the fan on and it is not helping my battery. The workshop who did this has not had this problem before.
My question is, does is anyone know if I can run a relay in the compressor wire somehow to solve this?

 

You can simply connect a normally open relay to the compressor clutch wire, and activate it via the 12V from the blower motor.

Or, a slightly better solution. If your aftermarket ECU has extra outputs, use one of them. That way, you can bypass the compressor during accelleration.

 

would you take the wire from the 12v input into the blower motor or elsewhere?