[duss46]

Hello all,

we've got a heating problem with a 2020 G07 X7 40i. 
The car is optioned with S4NNA 5 zone climate control and S536A Auxiliary heating. 
The problem appears ONLY in the first 2 rows, the 3rd row (5th zone) works OK.

1. You get in, start driving, the heating blows in 40-60 °C temp air per ISTA. 

2. After driving 15 minutes at operating temperature, the passenger side starts to blow in gradually colder and colder air, then it spreads to the driver's side and rear vents, at the end it blows in cold outside air (5 °C). 

3. If you let it idle and turn off the blower for 10 mins, heat slowly comes back, but goes away if you drive.

The only thing I noticed is the evaporator temperature: front evap temp 3 °C, while the rear one is 23 °C,  although I don't know if it's an error or not.

Changed: water pump, heat management module, auxiliary electric water pumps, IHKA, HKA, DME software updated. Flaps calibrated, initialised, deblock high-temp coolant circuit service function done, temp sensors values shows accurately what's happening in real time. Error memory is empty.

Our idea is to replace the heat exchanger, but that's hell of a job to do. 



Please let me know if you have any experience, thank you.

[weinerbarn]

Hello all,

we've got a heating problem with a 2020 G07 X7 40i. 
The car is optioned with S4NNA 5 zone climate control and S536A Auxiliary heating. 
The problem appears ONLY in the first 2 rows, the 3rd row (5th zone) works OK.

1. You get in, start driving, the heating blows in 40-60 °C temp air per ISTA. 

2. After driving 15 minutes at operating temperature, the passenger side starts to blow in gradually colder and colder air, then it spreads to the driver's side and rear vents, at the end it blows in cold outside air (5 °C). 

3. If you let it idle and turn off the blower for 10 mins, heat slowly comes back, but goes away if you drive.

The only thing I noticed is the evaporator temperature: front evap temp 3 °C, while the rear one is 23 °C,  although I don't know if it's an error or not.

Changed: water pump, heat management module, auxiliary electric water pumps, IHKA, HKA, DME software updated. Flaps calibrated, initialised, deblock high-temp coolant circuit service function done, temp sensors values shows accurately what's happening in real time. Error memory is empty.

Our idea is to replace the heat exchanger, but that's hell of a job to do. 



Please let me know if you have any experience, thank you.

How thoroughly did you bleed it, especially after changing the pump(s)? Maybe try vacuum bleeding it again before getting to crazy with changing parts.

[duss46]

It was vacuum bled according to TIS.

[weinerbarn]

I'm skeptical that it's the heat exchanger if it gets hot at all like you describe in the beginning. That evap temp seems suspect but it's pretty close to your outdoor ambient. Try it on air recirculate instead of fresh air and/or maybe temp block off the fresh air intake with cardboard to limit the cold air coming in for testing.

[duss46]

1701552116[/url]']
I'm skeptical that it's the heat exchanger if it gets hot at all like you describe in the beginning. That evap temp seems suspect but it's pretty close to your outdoor ambient. Try it on air recirculate instead of fresh air and/or maybe temp block off the fresh air intake with cardboard to limit the cold air coming in for testing.

We tried playing with recirculation, it didnt help.

[Krysiaman]

Maybe check switch valve in aux heater. I had similar problem in E60 when the switches valve stuck in “engine heating” position. It switches between heating engine and cabin by aux heater. Usually it’s located near aux heater assembly

[duss46]

1701596520[/url]']
Maybe check switch valve in aux heater. I had similar problem in E60 when the switches valve stuck in “engine heating” position. It switches between heating engine and cabin by aux heater. Usually it’s located near aux heater assembly

Auxiliary heating only works if the vehicle is not being driven, according to TIS

[Krysiaman]

That doesn’t mean it can’t be faulty. Just remove wheel arch and bypass webasto. It’s easier than replacing heater core

[mcrussell]

I had an issue with a air temp sensor in the heating duct on an i8 that caused it to blow cold all the time, it was reading 78 degrees, there where no errors in the car but after this was changed everything worked

[06apexxtx]

Seems the HVAC blend doors that control temperatures need to be reinitialized being the 3rd row has heat. Can do with ISTA.