[1.6 FSI] - Fan module + VCDS + HVAC

Evripidis

Member
OK here we go,

Fans will not come on. I read the wiring diagrams and the inhibit signals go through the ECU and the HVAC module.

1. The engine output tests will not turn on the fans at all.
2. I cannot connect to the HVAC module, too many comms errors.
3. I get 12v at the thick cable going into the module and ground connections are pretty good.
4. Ohm readings when cold indicate that the motor winding is 50 Ohms or thereabout.

I read too many posts about people having fixed theirs but no mention as to how. Or the threads are finished without any conclusion.

Any clues?

Regards,
Evros
 

4markowen

Member
Coming at this from my TT cabin blower fan, have the fans been sat for ages? Have you manually spun the fans for a good bit to loosen them up?

Not completely recommending it as I don't know the fans you're referring to, but I also gave the fan motor shaft a little squirt of lithium grease and a good manual spin of the fans until worked in and spinning more freely.

If the motor can't get going for the fan, that might be the route of the problem is my thoughts.
 

Evripidis

Member
I did give a good clean and spinning over while it was off the car yes. Thanks for replying. You are correct though. I'll try and get 12v to that motor.

EDIT: The fan spins reluctantly when supplied with 12v straight from the battery. Could that be it? I mean it spins but not full blast.
 
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PlasticMac

Member
The fan should rotate at a full rate of knots, with 12 volts direct, so the fan is the prime suspect.
See if Andy or Steve has one handy.
Mac.
 

Evripidis

Member
Hi Mac,

I have tried all the output tests plus unplugging the rad temp sensor. While I did this I checked the input signals with a multimeter and also checked the output to the fan connector. I got 10v to the motor (engine running didn't make any difference).

The fan won't move though so it is either a failing mosfet in that module or the fan. With what you are saying, I must get a fan.

Unfortunately Steve is unable to sell outside the UK and I am in Cyprus. I am going to have to shop around online and see what can be done.

Thank you all for your replies.
 

Evripidis

Member
I forgot to mention that the AC is completely deactivated....

You don't reckon that would have anything to do with it. It shouldn't really.
 

Evripidis

Member
OK, I revisited this today because the availability of the fan and the module are zero. None at the dealership and none at the motorfactors.

I took the fan out, disassembled the motor,cleaned the brushes with sandpaper and gave the metal plate a good clean.

I dipped the housing in vinegar for a couple of hours and then scraped all the rust off. Put it back together now the fan will run at full speed by using the output tests. The fan will only run for 15-20 seconds during the tests, is that normal?

Also when do they actually tun on, i.e., under what temperature conditions?

Evros
 

PlasticMac

Member
Great work @Evripidis Yes the short run is correct for testing.
I don't know how the fan is switched, other than via the HVAC Controller, there may be a simple thermal switch on the rad (my Mk1 TT has this), with the HVAC Controller looking after running it when the AC is On, which is not a factor in your case!
Maybe someone with a circuit/wiring diagram can help?
Mac.
 

Evripidis

Member
Hi Mac,

I did study the diagram in ELSA. It does indeed show that control goes through the AC module. I am guessing that the signal must be logically OR'ed between the ECU and the HVAC module.

I tried taking the fan module apart but I think it would be catastrophic as it must be potted at assembly.

Despite having no VCDS comms with the HVAC module, if the engine output test has been able to turn on the fan then this precludes the output signal to have been permanently inhibited by the HVAC.

I'll try and make the fan turn on this afternoon while driving around in the neighborhood. I am sure that the turn on conditions must be mentioned somewhere in ELSA. Hey ho, at least I found another leak and got to it while in the process. Oil cooler pipe hose.

Evros
 

Evripidis

Member
OK, job's a good'un. Fans confirmed working during normal conditions. Saved me a lot of trouble there!
 
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Evripidis

Member
I had a cold one earlier on. Thanks Andy.

It's not even mine! Belongs to my fiance. She would have dumped it ages ago. She has been driving my mazda 2 for quite some time now since I don't have to get around much.
 

PlasticMac

Member
I think there is a thermal switch, probably in the radiator, that controls the fan for engine cooling, and I'd guess it has an un switched 12 volts, so that the fan will run on, when the car's parked, if the engine still requires cooling. I don't think Audi would rely solely on electronics for the
1632235169972.png
engine cooling. If you Google Audi A2 Radiator Fan Coolant Switch, you'll see what I mean.
This is just my theory, based on the system in other Audis of a similar vintage.
The HVAC Controller looks after the fan in association with the AC etc.
Happy to be corrected...
Mac.

1632235169972.png
 

Evripidis

Member
Hi Mac, Indeed there is one on the bottom radiator hose (2 pins, F51 thermo switch) and another one on the thermostat housing (4 pins G2/G62 combo). Based on the diagrams, they both connect to the ECU and from there onto the fan mosfets. Functionality must be the same though and as you say.
 

PlasticMac

Member
Thanks @Evripidis.
Does the connector on the thermostat housing just control the "electronic" thermostat (unique to the FSI), via the ECU?
They must be chunky, late 20th Century mosfets, switching 6 - 8 amps inductive load.
In the TT, they are low tech relays!
Still the FSI is a technical "Tour de Force" (on a good day)🤔
Mac.
 

Evripidis

Member
Well, there is no way of telling from the diagram and I could not find any other information. The diagram does show two sensing elements and two sets of wires for G2/G62 meaning that the elements must be different and they lead to different pins on the controller. Surely one set must be responsible for the gauge temperature whereas the other set must be for closed loop control of the thermostat via the heating element as the kind people of this forum state.

Indeed very little to go wrong with the fan module, if I had a spare one to take apart I would. The control signals must be tied to the gates. It is a huge, chunky, potted OR gate I suspect. Maybe if the fan is on its way out then resistance would rise and then maybe killing it.

There is too much closed loop control on the FSI and for the era that is was put together most of it was still analogue, i.e., analogue signals being sensed back. Of course this is the latest model car that I have been servicing so I cannot say what exists on the later cars.
 

PlasticMac

Member
I've been reading VW SSP296 (Self Study Programme 296}, which describes the FSI engine. The cooling system is described as "dual circuit" with two thermostats, one for the cylinder head, which opens at 87C, and a second one for the cylinder block, which opens at 105C. Maybe that's why the thermostat connector has 4 contacts, 2 per thermostat?. The coolant flow is 1/3 to the block, and 2/3 to the head. SSP296 has lots of details, but I couldn't find any reference to the fan control.
If you want a read of SSP296 click here
Mac.
 

PlasticMac

Member
I've been reading VW SSP296 (Self Study Programme 296}, which describes the FSI engine. The cooling system is described as "dual circuit" with two thermostats, one for the cylinder head, which opens at 87C, and a second one for the cylinder block, which opens at 105C. Maybe that's why the thermostat connector has 4 contacts, 2 per thermostat?. The coolant flow is 1/3 to the block, and 2/3 to the head. SSP296 has lots of details, but I couldn't find any reference to the fan control.
If you want a read of SSP296 click here
Mac.
I've also looked at SSP222, which is all about the Bosch ECU, and it describes only one "mapped thermostat" which sounds correct for our FSIs.
Fan control seems to be from the ECU, via the Fan Control Module.
Find SSP222 here
Mac.
 

Evripidis

Member
Entertaining reads. I do remember bumping onto them in the past but I never sat down to go through it all. I'd feel a lot more comfortable knowing that the radiator sensor could turn on the fan on its own really. With a little bit of electrickery it could be done I suppose.
 
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