All fuses are fine, however there is no power on the fuses when switched on. Could it be the relay?

2010 RRS

yes it could

How can I test the relay? Is there another one I can swap it with to test?

It's R9 70amp grey one, same one (R7) used on air suspension could try swapping with that one. R6 is also the same but I think that is something to do with engine management, personally I would leave that one alone.

Cheers
col

Swapped the relay with the Ride Height Control and same issue. Ride height still works fine but windscreen heating still not working. I doubled checked the fuses and both are okay, but there is still no voltage passing through them.

I did however notice what I thought was the relay clicking every 10-15 seconds or so when it was turned on. Not sure if it should do that.

What do I check next? Could it be a faulty windscreen?

So to be clear.

You start the engine.
Turn on the front heater (not fans)
And no power at the 2 fuses ? how are you checking for power?
While ON, what happen if you remove and insert the relay ? Does it click ? if not, probably a fault with the heater panel or wire or low battery


A relay clicking every 15 seconds could be the heated mirror relay