CR140 - heater only hot on recirc?!

[1616Six]

Hi guys

Needing some advice please. My Mk6 2.0 GT TDI has lost its heat unless I have the recirculation button pressed. The car gets up to temp as normal still but the heating is freezing unless I press the recirc button but then naturally this makes the windows steam up!

Any thoughts?

Thanks in advance

Jordan

[Keithuk]

You need to get your motor scanned (preferably with VAG-COM\VCDS) for any error codes logged in the ecu and post them, that will save a lot of guessing.

VAG-COM\VCDS will test the A/C system components. The A/C system is great for demisting windows. The recirculation button shouldn't make the windows steam up.

When was the pollen filter last changed?

[1616Six]

The recirculation button shouldn't make the windows steam up.

When was the pollen filter last changed?


Thanks for the reply!

I thought the recirc button would make them steam up as it’s keeping the humid air in the car?

Pollen filter was changed around 3 months ago which has now made me wonder if that is the problem?!

[1616Six]

So I removed my pollen filter completely to rule it out and it’s still cold.

I just checked my coolant which looks fine, level hasn’t changed in the last year and no strange colours or oil etc

however... I just did a 50 mile journey and the actual coolant is still cold - dipped my finger in the tank and it wasn’t even warm.

Temp on the dash sits at 90c as usual

thermostat?

[Renars]

If coolant in expansion tank is cold but gauge on dash shows 90 degrees that suggests thermostat never opened since it starts to open at 83 to 84 degrees C. Gauge on dash will show 90 from 70ish to 120ish degrees C so its very missleading. Do another drive like this and check if radiator is warm. If not then thermostat never opened and isnt faulty. Could be some sort of a heating natrix problem.

[1616Six]

Hi

I did this the other day actually and the rad was warm but coolant was cold?

I've got a wifi Elm obd dongle somewhere actually which I could get an accurate coolant reading from via Torque so I'll try and find that out later.

It's actually booked in with a VW specialist next week to diagnose so hopefully I'll find out either way.

Thanks

[Renars]

It is manual or DSG ?

[1616Six]

Manual, I read about the second thermostat on the DSG's but nope mine is a manual!

[1616Six]

So the car has been into a VAG specialist today and it’s proving to be a very odd one...

thermostat is fine
water pump is fine
aux water pump is fine
heater matrix flushed
VCDS shows no faults, temp sensors all fine & flaps etc working

they established that the coolant is circulating around the engine and rad absolutely fine, temps are all consistent with nothing looking out of place. For some reason the heater just blows cool/Luke warm air at a push.

they did say one of the small hoses off the header tank has a small valve part way down and this was blocked/broken so they replaced it with straight hose whilst the part is on order and this has now allowed hot coolant to reach the expansion tank rather than being cold.

i needed the car back for the weekend so it’s booked in to have the pipe replaced next week and they will do more investigating but just no idea what it could be. they said all they can do is more trialling and that there’s an unlikely chance the matrix could be part blocked but you can’t tell from flushing. When I got home I took the under dash trim off & both metal matrix pipes were really hot so coolant must be getting through it?

im completely at a loss and am fed up now!

any thoughts?

[Renars]

Then maybe something with heater controls themselves?

[1616Six]

Then maybe something with heater controls themselves?

It did cross my mind but if you sit the car still for ages it gets warmer until you start driving which points to it being something mechanical.

[1616Six]

This is bugging me to the point of considering part exchanging the car if I can’t fathom it out soon.

does anyone have any thought as to what it could be?

To summarise...

thermostat is fine, up to 90c within 10 mins or so
water pump is fine
aux water pump is fine
heater matrix flushed
VCDS shows no faults and HVAC all working
metal pipes under the dash to the matrix are hot
rad gets hot
car never overheats
coolant looks clean

header tank was staying cold, VAG specialist found that one of the pipes to the tank had a valve inside that was blocked/broken so has replaced it with a straight pipe for the time being.


i still only get cold air blowing out. What on earth could it be?


My only thoughts now are either a blocked matrix that won’t flush out or something electrical that VCDS hasn’t picked up?

thanks

[Renars]

My bet on blocked heater matrix. I think its bypass unit and flush may not work.

[1616Six]

What do you mean bypass unit? Cheers

[Renars]

If it cannot get through it bypases and there is no heat given to air around. Like a safety measure to kerp coolant circulating.

[1616Six]

Ah I see

Well, I've just ordered a matrix so lets see if I can get it out without removing the dash..

[Renars]

My 1.6 tdi CAYC golf starts blowing warm air one minute after engine start since it has electric heater like all of them have (at least I think so) I guess 2.0 tdi also have this great feature. But seems yours doesnt work either if it has it.

[1616Six]

My 1.6 tdi CAYC golf starts blowing warm air one minute after engine start since it has electric heater like all of them have (at least I think so) I guess 2.0 tdi also have this great feature. But seems yours doesnt work either if it has it.

Tonight I’ve stripped most of it down ready, glovebox out & bits of trim removed in preparation & I can now see the end of the matrix.

Theres a lot more in the way compared to the mk6 Jetta how to & a different matrix too. I seem to have more electrics around mine.

if I do have an aux heater then no it’s not working but VCDS isn’t showing any faults.

[1616Six]

I have heat!

Appears to have been the heater matrix.

very easy to get out.. absolute pig to get the metal matrix pipes into the new matrix. Managed to get one clamp on but the other one just will not seal tight enough to get the clamp round.

After many hours of swearing at it and pulling muscles (I’m not a contortionist) I’ve given up and booked it into my VAG specialist to fit two new clamps then I can put the interior back together.

I did however start it up and somehow even without the clamp it doesn’t leak a drop so I did a good 30 mile drive and it was amazing - I was actually hot!

I am absolutely shattered but seeing the light at the end of the tunnel now I hope.


https://preview.ibb.co/gmZ7j6/A686_C8_AF_2779_4831_873_A_C878_DC2_AD80_D.jpg (https://ibb.co/gAi046)
https://preview.ibb.co/hCD046/6_FF891_EB_6_C2_C_43_A7_B969_C86982_DCAEA6.jpg (https://ibb.co/fXuUxR)
https://preview.ibb.co/f48pxR/DAB5_DF96_65_B2_401_A_8271_D55445_C4_C330.jpg (https://ibb.co/gU0PWm)
https://preview.ibb.co/jhiNHR/D843_AAB6_F3_E9_4033_BFBD_2_E1941_CC026_C.jpg (https://ibb.co/jDaDP6)
https://preview.ibb.co/jbPwcR/575_DAD14_68_B4_4728_9_E6_D_2_EC96_FF05_B1_C.jpg (https://ibb.co/b9s4Wm)
https://preview.ibb.co/gpydrm/97_B2_D471_FEBC_4_F38_81_AD_ED20447_A803_E.jpg (https://ibb.co/kwsSj6)

[Renars]

In the last picture its the electric heater element I guess. Why didnt that work ...

[1616Six]

That's the next thing to work out :)

Just glad to have heating back!