Long drive in the car today and I have heat out the vents +++

Flushing both matrixes means they are now clean, unblocked and importantly balanced so not upsetting the system. New G150 is working as it should also.

Heat out of both side vents as expected and the climate makes the cabin warm as expected when 22c or 24c and cools it correctly when I set to 20c.

So that's another job ticked of the list on the A8.

I must admit the 2.8 is far from fast but its a comfy cruiser and well suited to the recent poor weather we have been having.

Glad yours is working. The HVAC is now completely and spontaneously broken in both my working D2s :mad:

Big Red used to work absolutely fine in the summer. Now she has no temperature control whatsoever. Max heat from the side and lower dash vents and no heat at all from the centre vent and the windscreen. No response at all to the temperature settings or the control in the centre vent. Set the cabin temperature manually by adjusting combinations of vents.

The S8, already having max heat from the right hand dash and lower vents, now also has almost no air coming through. The blower is working and makes a lot of wind noise on full chat, but barely a draught out of any of the vents regardless of setting.

Most frustrating.

A challenge to your IT and diagnostic skills?

I have put a huge amount of time into working out the HVAC system and going through it with VAGCOM.

It’s damn complex and frustrating but over the past four weekends I have got a better understanding of it now.

My S8 shows me the same readings across all the measuring blocks as the A8 and appears that it should be working.

Though my S8 also blows hot for no apparent reason out the right side vent which I control the temp by turning the vent open or closed!

That’s a task for another day +++

One hot side I think is the valve block stuck open. I had both sides hot until I swapped the block, now the passenger side works properly but the driver's side is still hot.

Since you've studied it, do you have any ideas on the lack of airflow or lack of temperature control?

Its the next project is the S8 heating as right now I am not sure why one side is hot and not the other.

Its either going to be mechanical (Motors/ Flaps) or the HVAC system thinks it needs to put heat out there.

One thing I did do on the A8 which I will do on the S8 is even though the VAGCOM basic settings told me the flaps were moving was to do a basic check. Hence I pulled the head unit out and used a sharpie to mark the white round plastic wheels on the motor flaps so I could actually see them move.

All was OK, I just did not 100% trust the VAGCOM readings.

My pump has started playing up now! How annoying a quick tap of a ratchet handle restarted it, but I can see me taking it back out to check the brushes and armature. Or maybe just fit a different auxiliary pump in the pipe in a convenient location almost every car now has these fitted now.
While doing a health check I noticed that the thermostat was stuck open a little slowing the warm up. rad getting warm pic 2 and my pipe into the matrix got to 57 degrees quite quickly but the car didn’t reach 90 and I ran out of time. so I’ll have to test that again pic 1 shows pipes at the air bleed outlet is cooler and I’m not sure if the pump was running then so I’ll test again. Use a long screwdriver against your ear(handle end) and the other end on the pump to listen to it.
Dave

You're very lucky if you need a listening stick to hear that pump. I could hear mine over the engine so just disconnected it.

Replacing that whole block of over-complicated misery with something simpler is definitely the way to go.