Looking at the bottom of the UK drivers side A pillar under the carpet as suggested in another thread cannot see any ground points. What I do have is a fabric taped cover heading upto the fusebox.

Well that's all the diagnostics I can do done, cannot see anything odd and everything checks fine.

Seems the controller J126 is not switching to 12v when commanded.

I wonder if A8Parts would send a known good fan speed controller to me FOC so I can at least rule things out, I cannot trust my original or the other used one I ordered from elsewhere. I would of course pay for or return the part depending on outcome.

I am sitting in the car now writing this, engine is on and the fan is outputting lovely cool air at 3c according to VCDS via solar power of course.

I've finally had enough of trying to fix this problem, so today put the whole blower motor assembly back together and took the car for a drive.

It's not been anywhere for weeks and covered 60 miles since mid July.

I did not drive far, about 6 miles or so. Enough to warm up the engine , and put some charge back into the battery which I leave disconnected anyway.

Can confirm the problem is still present, and not fixed. Solar power still working great but that's it.

This is weird

So yesterday and today I've driven the car to work and back, and whilst sitting in the car park this morning the heater fan sprung into life, worked for about 30 seconds producing lovely warmth and then stopped again.

Remember the fan works perfectly fine on solar, I really have no idea what's going on.

it almost sounds more like an earthing or connector problem of some kind Manny. I had an issue with the Electronic Handbrake switch on a D4 and it turned out to be the handbroake module having loose / poorly made connections, so after I had all of those re-secured it has been sorted since +++

Its weird, the motor must have a ground connection as it runs on solar. I've checked using a multimeter and all seems fine with regards to the incoming voltage.

I actually drove the D3 to hertfordshire last weekend, 350 mile round trip and on the Dorset to Herts leg the A/C actually came on around Winchester for 5 minutes and I had full control of the fan speed from the A/C controls. Get to Basingstoke and it's off again and did not work anytime after that when driving during the whole weekend except on solar.

If the sky is clear, the fan continues on solar power pumping a very small amount of lovely cool air into the cabin even whilst driving.

You are right, it sounds power related but no amount of wire wiggling in the blower motor housing, or even behind the climate controller gets it working again.

No fan fault listed in VCDS, just the implausible signal because the unit is trying to run the fan but it is drawing 0 amps.

Tempted to buy an aftermarket new unit from Germany to see what happens, but that's just under £100 plus delivery.

Just guessing here, because I know very little about these newfangled D3s .... but is there maybe some kind of fan speed controller that could be at fault? The power coming from the solar panels will be quite weak, so it's likely that it bypasses any fan speed control device to enable it to give every bit of power it's able to deliver directly to the motor. In fact I think Andrew had a similar issue with his D2 blower, did he not? If I understand correctly, the D2 has some kind of inline power/voltage regulator (aka 'the hedgehog') which was a likely suspect in his case. I'm wondering if the D3 has a similar power control unit.

Is it really running from solar when ignition is on/driving? Or is it just oncoming wind going through it and turning it? If it's definitely running from solar then it is not switching over as you cannot have solar and battery connected at the same time. On D2 it's separate relay doing switch over but on D3 I don't know, it could be internal relay inside climate control unit.

I don't recall the relay setup, but the solar power circuit in a D2 totally bypasses the hedgehog and all other controls and basically just connects the panel straight to the fan motor.
It really is a simple setup; I think Ian (IT) documented the retrofit here long ago.

I only really looked at the circuitry in order to fit a cutoff switch, which I placed in the earth side of the solar panel circuit. Easily accessible around the front passenger footwell.
My (failing) memory says that I thought the relay was actually in the HVAC unit, but it may be that it's an external relay and the HVAC controls it.
Either way, the D2 relay is in the more complex +ve circuitry, which is why I went for the solar earth for my switch.

I would expect (hope) that the D3 didn't "reinvent the wheel" so follows a similar pattern/logic.

My fan motor problems (currently not manifest) were equally evident in either mode by the way.

It's definitely separate relay on PF D2, maybe in FL they moved it inside AC unit.