Auxiliary Relay for Blower & AC Control in Parking Heater?

Good evening, fellow diesel mechanics!

I'm currently installing an Eberspächer auxiliary heater in my Bora (engine code: ATD; with manual air conditioning).

Here's the problem I'm encountering: According to the attached instructions, why is a second relay required for the climate control system? (see diagram 4)

I would now only connect the blower to the relay as shown in diagram 3. What is the disadvantage of doing that?

Thank you for your responses!

Best regards,
Findus.

Hi Findus!
As I understand it, the second relay prevents the air conditioning from being turned on. In any case, the AC switch will definitely not light up (if it's pressed), and you might also have the problem that the radiator fans are activated (depending on how the electronics behind the VW switch are powered).
I only needed to install one relay with my Webasto TT-E in my Polo 6NF. But as I said... check how your vehicle is wired behind the switch!

Best regards,
pretzelman01

Okay, you're welcome!