Driver's side Vent (RHD) always blows colder

[Jacobb5179]

Hi Everyone, first of all this forum has been a godsend on many occasions so thank you to this awesome community!

My 2.0TDI fell foul of the 'Mit Silikat' issues and started boiling coolant due to a blocked heater matrix, the lack of heat in the cabin was not noticed due to it being summer. I have had the system flushed, teabag deleted and a new matrix fitted, works great! However since I've been paying attention I've noticed that the drivers side vent (the one right next to the window) is blowing significantly cooler than the rest of the blowers, even the one next to it! 3 are blistering, I can't hold my hand against them, and the other is just mildly warm.

When I run A/C MAX the vent in question is suddenly bloody freezing and the passenger side vent is mildy nippy, bascially the reverse of the heat! I've always been impressed with the AC on this car, but maybe its just my vent is getting super cold!

My questions are:

- Is this normal?
if no:
-Does each vent have its own control flap and temperature probe?
- Is this something which is common, what are the main culprits?

Any crumbs, clues, or suggestions would be very helpful indeed!

Thanks in advance guys!

 

[SuperV8]

I don't believe each vent has it's own flap motor control, just left and right and up and down, but looking at the main air distribution housing there looks like 4 flaps! I don't know how these are controlled?
The central 2 have white rubber seal's so presuming these can be closed off completely - but the outer 2 don't so presuming these always allow some air flow for side window clearing.

Maybe try a flap re-calibration?

Number 5 is the central air guide

 

[Jacobb5179]

Thanks V8! I have noticed that the side vents leak air no matter what setting I am in, this was a worry of mine but the pictures make so much sense!

I’ve done the flap calibration and it didn’t really help…however I heard a gurgle a few days back and suddenly it’s all much better, but still not perfect.

Does anyone know if certain vents get heat from different parts of the Heater matrix?

Thanks again!

 

[SuperV8]

Thanks V8! I have noticed that the side vents leak air no matter what setting I am in, this was a worry of mine but the pictures make so much sense!

I’ve done the flap calibration and it didn’t really help…however I heard a gurgle a few days back and suddenly it’s all much better, but still not perfect.

Does anyone know if certain vents get heat from different parts of the Heater matrix?

Thanks again!

Yes, certain areas of the matrix feed different vents - which is why the common symptom of a blocked heater matrix is when the drivers side is colder - as that side of the matrix it putting out less heat.

A gurgle would mean you have/had some trapped air (so the end of the matrix which feeds your drivers vent has poor coolant flow and less heat transfer) - There is a diagnostic activation you do after changing the heater matrix which tries to purge air out by running the micro circuit pump, but this would normally happen naturally over several heat cycles.

 

[Jacobb5179]

Thanks for the info! I did the matrix myself, I’m worried about how well the system was flushed and half expecting a blockage again. I didn’t know about the diagnostic run, served me right for doing it DIY! Fingers crossed it stays (reasonably) warm!

 

[BillyCool]

The gurgle can be some residual air - the system is supposed to self bleed. Just keep checking your coolant when cold and top up if needed. When I changed my matrix it took a few weeks and top ups to finally get the air out and up to temp.