D3 heater/ac fan problem
 

So, i guess as a result of lack of use my D3 heater blower has sort of stopped working.

Because the blower motor runs perfectly fine when being powered by the solar sunroof, I don't think its the motor itself.

So today I installed a replacement fan controller in the blower motor housing, and the result is still the same. Runs fine when left in the sun and engine off.

However today was really sunny and I discovered the fan is actually running with the engine on, but it's stuck in solar mode. Switching the system off and the fan still runs, disabling the solar sunroof running makes no difference and the fan continues to run.

So the blower fan is stuck in solar mode by the looks of it, is there a switching relay like on the D2?

I did having it running properly for a couple of days a few weeks back and it did work briefly this evening until I turned the climate control off and the blower would not switch back on when I turned it back on.

Manual fan speed adjustments make no difference, neither does setting Lo or Hi.

On a D2 switchover to the solar panel driving the fan is controlled by the HVAC system; I can't recall if there's an external relay or the solar panel is just wired straight into the HVAC and it's switched inside.
(I ought to recall, I've messed with it and it is VERY simple)
I wanted my D2 solar panel to be disabled with a switch and in the end I did that by cutting it's "earth" circuit and looping it out to a switch I installed. If there had been an accessible relay I would have done something to that.
(Awaits more informed opinions...… ;) )
As for a D3 who knows?

I found a current flow document on here, it details J355 as the solar operation control unit and appears to reside inside the car headlining.

Also found mention of J126 where the supply from the roof appears to plug into. It is J126 which I have replaced (I think) this in turn is connected to the climate module.

It is worth noting that I replaced the part with a used one from a newer car.

Really stumped now, I'll have no job in 5 weeks and I have this car which is eating money I cannot afford to lose.

I've hooked up VCDS and have this code regardless of which controller (old or new) is installed.

I did clear the codes, and it comes back with the other usual ones I have.

Worth pointing out the fan did run earlier with no problem.

01844 - Control Module for Fresh Air Blower (J126)
008 - Implausible Signal
Freeze Frame:
Fault Status: 01101000
Fault Priority: 3
Fault Frequency: 1
Reset counter: 91
Mileage: 271398 km
Time Indication: 0
Date: 2003.02.27
Time: 00:10:42

Freeze Frame:
Temperature: 23.0∞C
Speed: 0.0 km/h
(no units): 8.0
(no units): 169.0

Research suggests in the blower motor despite the fact it runs fine on solar, any thoughts.

I'll reassemble the car tomorrow with the original controller, and I'll have to sell it with faulty blower, i've had it with this car now. I cannot afford to fix it.

Chances are that on solar it's a fairly direct connection to the fan, with no speed control.
In normal use it will be powered via a speed controller, so it suggests the fault is in that system "somewhere".

I've checked all the connections, and put a multimeter measuring volts and everything appears correct entering and exiting the controller. I've got ground, 12V coming in, I can see 4 volts coming into the same controller from the sunroof, its just weird and i've lost all patience and run out of money.

here is a video I just shot, as you can see the blower works normally in solar mode.

https://youtu.be/CTd5gmO3vyg

There are no fault codes against the motor, just the control module.

Just a thought does anyone have a J126 controller knocking around, that I can borrow. You never know but the used one I got could also be faulty.

I'll then buy it off you, if it works or return it.

Part number is 4E0820521

Still battling on with this, took interior apart and checked connections behind climate module and all is good.

Tried swapping old and replacement J126, still the same.

I had a look at measuring blocks and things look wrong here.

Address 08: Auto HVAC (4E0 910 043 )

10:29:02 Group 044: Fresh air blower V2
0.000 A Current actual
0 h Solar usage
0.00 V Voltage actual
5.80 V Voltage specified

The voltage specified goes up and down with the fan speed selection, but actual remains zero.

Switch engine off and solar kicks in and fan starts, and will then stay on solar even with engine restarting although VCDS is reporting zero volts.

Unlike a lot of other threads, mentioning lack of fuse 44 my D3 has one. Should have checked first before rooting around under the passenger carpet to discover mine is not there like in this post. http://forum.a8parts.co.uk/showpost....46&postcount=6

Anyway fuse was good, so now I am going to check the ground connection. Interestingly I removed the drivers side sill trim to get access to the grounds and now the car will not start either, and the starter is on the same ground point.

Another observation, with fuse 44 removed, I get 12V on one side of the fuse, and the voltage from the solar roof feeding back on the other side.

Another observation, with fuse 44 removed, the solar function of the fan continues to work and the fan spins.

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.

Someone will have and be able to interpret the D3 wiring diagram; it sounds to me EXACTLY like the relay isn't switching.
That of course could be a faulty relay or a failing trigger signal (or wiring).

The solar panel is connected directly to J126 blower control unit. That appears to have a single connection to / from J255 climatronic control unit.

http://forum.a8parts.co.uk/attachmen...1&d=1568747638

So "almost, but not quite, totally unlike a D2". I guess V2 is the blower motor and J355 the solar panel?
What is C20?

C20 looks like the solar panel to me, judging by the symbol. So I expect J355 is a DC-DC convertor (probably stepping up/down the solar panel voltage to provide a consistent, regulated output).

Indeed, I didn't look properly at the C20 symbol. Another level of sophistication over the D2, so probably almost nothing to learn from my/our comments I'm afraid. :(

Yeah C20 is the panel, J355 is the regulator.

J126 is the part I replaced, but the replacement I got was a used one from a car of similar age.

It's quiet possible that the used one is also faulty, so I might go ahead and buy the new no OEM one from ebay.

J126 is what controls the fan speed, it has a number of inputs, and just two wires going out to the fan motor itself.

The fan is definitely running on solar power when the engine is running, you can see it spinning quiet happily by looking into the box with the pollen filter removed, ant it's speed varies based on the amount of sun.

There is 12V coming into the controller from the car side, and the voltage from the sunroof varies based on the amount sun.

It is possible of course that J255 is faulty, in that maybe the required signal is not getting to J126. I have no means of checking this as I do not know what the signal that controls the speed of the fan into the controller is meant to look like. J255 has component protection, so it's not easy to just swap a replacement in.

From the SSP it looks like J126 is on the LIN bus so tricky to see what J255 is telling it.

I found a document explaining the LIN bus, I guess its working because I don't have any fault codes except the implausible signal from J126. I do not have the no communication fault mentioned in this document.

http://www.volkspage.net/technik/ssp/ssp/SSP_286_d1.pdf

I think it's safe to assume that default mode for J126 if it does not receive signal is to switch to solar for example when ignition is off and climatronic is switched off. So it looks like J126 in not seeing signal from J255 either because it is itself faulty and does not sense signal, there is break or short in wiring or J255 is faulty and not sending signal. You could start checking for break or short in wiring with multimeter and if you have oscilloscope you could check if there is any signal coming out of J255 and if it is reaching J126

If you do not have oscilloscope you could try connecting small high impedance speaker like from old phone, it's quite low data rate bus so I think if there is any data going you should here some noise.

Did you ever fix this. My fan is erratic as well, I was thinking it's the fan itself and I do have a new fan ready to go in. I was going to do it today but looking at the work involved I was thinking if I should get the regulator on standby as well just in case. Don't fancy taking it all apart in this cold just to find out that it's not the fan as I found out that even when fan is working measuring blocks still show 0.000A

I noticed that mine was more likely to work when doing left turn and more likely to not work when doing right turn. So it seemed like classic brush/commutator wear problem. As a result I attacked it without spare control module on standby and it was faulty fan motor and now with replacement aftermarket fan it works as it should. Comparing to D2 there was a lot of stuff to remove to get to it but it was easier overall. Also drawing comparisons I can say that on D2 when it failed the brushes were very low and commutator was worn through but on D3 the brushes are low but very little wear on commutator. Could be that copper alloy or brushes are more advanced on D3 resulting in less wear to metal in D3 or maybe somebody already replaced brushes on my D2 in the past and it had already gone through 2nd set. D2 had solar roof and fan failed about 130k, D3 no solar and 180k miles. I guess I will see if I can get replacement brushes for original motor, replace then and keep t as spare or sell on.

Slightly OT but this sounds similar to an issue I had with my very first Audi, a brand new '95 A4. Only noticeable during the colder months and when on a sweeping left turn (usually roundabout motorway onslip). Heater would be blowing out hot air and then on taking the onslip, it would blow out cold air until going straight again. Dealer response was 'no issue found' (just like all the others!)