Help - No Heat - dash stripped and Pics included

[TdiBlacky140]

Ok folks, cold winter is here and I have a issue of no heat in the cabin, would appreciate some help as its cold these mornings. mk5 2.0L Gt sport if that helps, no fancy climate control, just the basic 3 knobs and air/con.


So, I get hot air for 1 min initially, then just blows cold air.


The main question I need answering is regards the knob that controls the temp from cold to hot, is this knob supposed to be attached to something like a wire cable? Mine isn't, although it looks like it should be, but I can't find any loose cables, etc, at the back of it that might have dropped off. How does this knob control the temp? I've attached pics below, please look at the 1st knob and if anything is missing.


Is there a flap or something that directs / passes the air across the matrix rad to give hot air,,, i've read of this is how it works, but what controls this flap, is it the temp knob and if so how does it do it if not via a cable? Is it electrical?




The below test explains what I've done so far, checked, noticed, etc....


I've stripped down the centre dash and removed the glove box. I can see the re-circulation flap above the blower motor and this operates fine when I press the button. The motor itself is blowing good too. There's a recently new pollen filter in it.


Regarding the control unit with the 3 knobs, the knob for controlling the direction of flow towards windscreen, head, floor ,etc,, works fine, I can see it attached to the cable and I can see the flaps open and close appropriately and air comes out.


I've bled the coolant, the level is fine and never moves, I checked both hoses going from the engine into the cabin heater matrix rad and both are hot suggesting the rad matrix is ok and not blocked.

[TdiBlacky140]

Just to update:


I just checked to see if I could hear a motor when I turn the knob from cold to hot and I could, even better,,, I can actually see the flap it's opening / closing, it's down the back behind the radio, when I turn to cold the flap opens and I can then see the rad / matrix behind it, when I turn it to hot the flap closes.

I noticed there's no in-between position of the flap, it's either open fully or closed fully, is this correct? If I turn to the middle for example the flap is closed, from about half way bwteen cold and middle temp the flap starts to close and closes fully.

I left it running on no.4 setting and heat up full just to see if the flap would work it's way open and hence cause the fault of 1 min of hot air and then cold air but the flap stayed closed.

I'm not sure what else to check now?

I thought the matrix . rad was more under the drivers side footwell, this rad I could see now is behind the middle of the dash centre console,, looks a real pain to get to if needed. Is there 2 rads in the interior, just so we have the terminology right, the matrix and rad are the same things, yeah?

[john942s]

I think the heat flap is probably thermostatically controlled. Find the sensor and test or replace it.

[TdiBlacky140]

I scanned it with the engine running on idle and the air/con button switched on and the blower on setting 2 or 3, this morning after a long drive to work. Pics below!


It seems to think the a/c is actually switching on???
Measuring block no. 001 doesn't show me anything, is that where the "shut-off" value would be? Perhaps it's not showing anything in that block because it appears to think the a/c is actually on?


By the design of the a/c system in this car, can the a/c actually be on if the 2 rad fans aren't on? I was under the impression the fans come on when the a/c is switched on and if the fans aren't running then the a/c won't actually switch on, am I correct or incorrect in thinking that? Maybe its possible for the a/c to work without the fans if the outside temp is cold enough?


Also, I notice that in measuring block no.3 there is a value "Engine Speed Increase = OFF" ,,, I've never noticed the engine speed increase when at idle when using the a/c, is this because this value here is switched off?


Also in measuring block no.3 do the values of 35.2% + 36.8% indicate VCDS thinks the fans were running? Neither of the fans was running when I ran this test despite the a/c was switched on.


The refrigerant pressure has changed from 4.4 bar when a/c was off and to 10 bar now with it switched "on"?


Appreciate opinions / feedback on these latest results.