Need a diode between the new relay and the dk grn wire and a flyback diode on the relay. Maybe just the flyback would be ok.
But, I see no use for it at all.

 

A larger aluminium radiator would be a lot easier and more efficient, and you wouldn’t have to explain the extra wires and stuff at the point of ignition to your insurance company after the fire.


https://zzperformance.com/products/z...diator-for-hhr

 

I agree that it's not needed. I just liked the mental exercise. So from a non-electrical guy, pleased to explain that the need for those diodes. I know what a diode is. I just don't know why it's needed or what kind of reading rating would be appropriate.

 

Like a check valve.

 

A one way flow of electrons.

 

When relays release there is usually a surge (flyback) the diode prevents it from doing damage. Some relays have a diode built in.
The other one would be needed to prevent the 2 ground signals from confusing things.