heater fan- blow or suck?!!

[elmsoft]

I recently switched the heater blower on my 05 plate Touran and now nothing comes out of any of the outlet vents regardless of the selector position.
Curiously though, when I open the re-circulation inlet the cold air blasts out.
It is as though the fan is working in reverse!!
Any one any thoughts on this?

Thanks for reading

 

[Avocet]

Do you mean cold air blasts out of the vents? (Or from the air inlet for the recirc air)? If it's the former, then it suggests a blockage to the fresh air intake - perhaps a completely blocked pollen filter or leaves all over the grille where the air comes into the heater box (usually at the base of the windscreen on most cars).

 

[elmsoft]

Sorry I wasn't clearer. There is a motor driven hood or flap on top of the fan assembly and this opens when the re-recirculate switch is operated. This is where the cold air comes from when it is opened. Very little air comes out of the windscreen, foot well, face level vents, with any settings. I removed the pollen filter and this makes no difference either. i have also checked for blockages as far as possible. Certainly there is no debris that I can see at the external intake.
For all the world it seems as though the fan is blowing when it should be sucking.....As though VW makes both kinds and I have fitted the wrong one!!!
And yes, it has occurred to me that I have lost the plot!!!

 

[Burnerman]

I know the ventilation flaps on these are fused....worth checking each and every one as I've no idea which fuse it is! Some of them aren't accurately labelled on the fuse box lid either
John

 

[Avocet]

Sorry I wasn't clearer. There is a motor driven hood or flap on top of the fan assembly and this opens when the re-recirculate switch is operated. This is where the cold air comes from when it is opened. Very little air comes out of the windscreen, foot well, face level vents, with any settings. I removed the pollen filter and this makes no difference either. i have also checked for blockages as far as possible. Certainly there is no debris that I can see at the external intake.
For all the world it seems as though the fan is blowing when it should be sucking.....As though VW makes both kinds and I have fitted the wrong one!!!
And yes, it has occurred to me that I have lost the plot!!!

That's interesting then! But presumably it used to work OK and you haven't changed the fan? I'm not familiar with the Touran, but pretty much all the cars I've seen, use centrifugal fans for their heaters. The blades look like a cylindrical cage with fins on, rather than the "propeller" type fans for cooling the radiator. If the wires are the wrong way round, a centrifugal fan won't "suck". It will still "blow", but a bit less efficiently than if the wires are the right way round (because of the aerofoil cross section of each blade facing the right way when it's rotating in the correct direction).

The recirculation flap either allows the fan to pull fresh air in from outside the car, or, (if the flap closes that inlet off), it forces the fan to take air from somewhere inside the cabin (usually behind the dash) and blow it back into the cabin. Useful either when there are fumes outside, or when the car is very hot and you're then passing the same air through the air conditioning evaporator several times, getting cooler each time, rather than pulling hot air in from outside the car.

Somehow, it looks like when set to recirculate, everything is working fine, but when set to pull fresh air in from outside the vehicle, there is something preventing the air from coming in. Has the car been laid-up for a while? Is the mouse nest somewhere in the ducting? If you haven't changed anything, it must be some deterioration, rather than anything that could cause it to work differently.

Apologies if any of this is telling you stuff you already know!

 

[elmsoft]

Many thanks for your careful and knowledgeable reply. And yes the fan is definitely the cylindrical cage type, not that the plug allows the wiring to be wrong.
I've hunted without success for the mouse nest.
And I still reckon the recirc system should suck not blow.
I'll keep thinking. Thanks again.

 

[elmsoft]

I know the ventilation flaps on these are fused....worth checking each and every one as I've no idea which fuse it is! Some of them aren't accurately labelled on the fuse box lid either
John

Worth a try. Easier than dismantling the whole dash which is my next option

 

[Burnerman]

If it has climate control then it could be a module fault.....do plenty of research here before pulling the dash out!
It could be as simple as a linkage disconnected.
John

 

[Harry Bloomfield]

I would suggest it is due to powered flaps, failing to operate, if the fan makes a noise when it is supposed to run.

 

[elmsoft]

If it has climate control then it could be a module fault.....do plenty of research here before pulling the dash out!
It could be as simple as a linkage disconnected.
John

Good advice . Thanks

 

[elmsoft]

I would suggest it is due to powered flaps, failing to operate, if the fan makes a noise when it is supposed to run.

The fan makes plenty of noise so I will take your advice and check fuses to start with. Maybe I'll get lucky

Thanks everyone

 

[elmsoft]

This is more a blog now than a request for help!
Removed tonnes of stuff.
The under bonnet scuttle - So I can see the air intake and clear daylight where the fan was
Passenger side footwell duct . Clean and clear as new
Radio and heater controls show the bowden cable is working fine selecting windscreen, face vents etc.
The servo flap control seems to have a very limited range- no idea what it should be.
A vacuum cleaner set to blow instead of the fan doesn't produce( much ) air at the vents.

I'm refusing to give up and if I end up with a garden full of interior fitting then so be it...
Thanks to all for suggestions and even just reading!!

 

[Burnerman]

Does the fan speed increase as you turn it up?
Fascinating, this one!
John

 

[Avocet]

I'm out of ideas too, but very interested to hear the outcome! I wonder if there is a flap, somewhere in there, that is causing the air to take the path of least resistance so that it works when in recirculation mode, but just swirls the air round and round the heater box when in fresh air mode? Can you lay hands on a scrap heater box or an exploded drawing of one?