No hot Air from Heater -Climate control all ok. Main dealer wants ££££££ to investigate

[jzbdski]

Hi,

My heater has stopped pumping out lovely hot air. It feels to me that it has done this very suddenly -ie. it hasn't gradually got worse, it just stopped and no only pumps out cold air.

I've been trying to look into what might be causing this and things like a faulty thermostat, a clogged heater matrix, dodgy motor or stuck blend flap have been cited as possible causes.

As its something a little esoteric, I spoke with my main dealer but the figures they were quoting were truly eye-watering.

So, I'm resigned to trying to attempting to investigate a bit myself, if only to narrow down the list of possible culprits.

My car is a run out 2015 model A4 Avant Tecknik with the 2.0l 163 ps ultra engine. It is fitted with a 3-zone climate control and was re-gassed in the summer.

The A/C appears to still work and, thankfully the drier is doing enough to clear a steamy window -just.

Ive had a good look and here is the info i've gleaned:

Im not low in coolant, nor am i losing any.
The engine is not over-heating, and the gauge stays bang in the middle.
Both pipes to the heater matrix are equally hot, confirmed by thermal imaging, which would imply that it is not blocked and that coolant is flowing freely through it.

I Have VCDS and have run the general scan and interrogated the Hevac system with no faults found.

I did go through the manual stepson VCDS and, again, no issues were found with the heavy but it didn't blow hot air when it should have and, if I'm honest, it felt like the fan, while making all the right noises, didn't really seem to circulate air at any great velocity.

Where should i be looking next ?

Is there some way in VCDS of definitively resetting the flaps and running the blowers in such a way that a failure would br obvious ?

There isn't something daft like a fuse which could be causing grief is there ? -or would that show up in VCDS too ?

I should also add that the auxiliary heater is switched off (I seem to remember being told it was a fire risk or there was a recall or something) and I did recently have a spate of electrical gremlins which seemed to be caused by an intermittent signal from an ABS wheel sensor. Once cleared, all of those issues (abs, stability, TPMS, Parking brake, etc) went away.

Thanks in advance for any help, advice and guidance you can offer

from a very cold Scotland

[Whippy53]

Have you had any water intrusion? Check floors on both sides. Possibly a fault with the flap motor, so yes, check the fuse.

[jzbdski]

Hey Whippy,

No sign of water ingress on either side

[Crasher]

What is the VIN?

[jzbdski]

Hi, the VIN is:
8KXFA1580**

Another garage has looked at it reckons the thermostat is ok, no coolant leak and no faults found in diagnostics.

They’re pointing towards the heats matrix being clogged.

Only thing is, I had a good look there with the thermal camera and both I let and outlet pipes seem to be at a similar temperature so would that point to there being no blockage ?

Would a malfunctioning flap raise an error code in VCDS ?

Is the temperature flap one of the ‘easy’ ones under the glovebox ?

Or ought to I have 3 given that I have 3 independent CC zones ?

Short of taking the glovebox out and physically eyeballing the flap motors is there a definitive way to test the blend flaps and read input by and output data (eg actual flap position) ?

Thanks again

Richard

[Crasher]

A partial VIN is no use to me and it is not GDPR relevant data, if you are still worried, private message me it.

[jzbdski]

A partial VIN is no use to me and it is not GDPR relevant data, if you are still worried, private message me it.

Hi,

Sorry if I’m being dense, but why do you need my VIN ?

-overly cautious Richard

[MFGF]

Hi,

Sorry if I’m being dense, but why do you need my VIN ?

-overly cautious Richard

Crasher has access to dealer-level systems that can tell him the exact spec of your car if he has the VIN, plus access to any technical bulletins etc relevant to the car specifically. I completely understand your hesitance, but he's one of the good guys :-)

Cheers!

MF.

[jzbdski]

Oh, ok, I mean, there’s nothing to stop anyone taking a picture of it in any case !
I’ll attempt to PM you if I can get it to work on my phone.

Thanks for the help

Richard

[Crasher]

There are no TPI's on the subject but it has two additional electric water pumps, one specifically for the heater, so check they run in output tests. Prod me tomorrow and I will did deeper, I need to go home and degrease after putting the sump back on a 2017 A4 that had a massive oil leak and I am covered in it.