C6 blowing hot constantly one side only

[Orbit Motors]

Good evening,

My 2006 C6 has an issue with the Air Conditioning where the drivers side is always wanting to blow ridiculously hot air regardless of what temperature it is set to. The passenger side appears to be working normally.

I've plugged Diagbox in to watch the live data that shows the temperature of the air being blown on each side of the car. The passenger side shows results that you would pretty much expect (about 12°C which is similar to today's outdoor temp here), but the drivers side is showing a constant temperature of -30°C (yes, minus 30) regardless of fan speed or temperature setting or anything.

Can I assume that a faulty sensor reading is causing the AC system to think that the drivers side of the car is constantly freezing and it needs hot air to bring it up to temperature?

TIA

[GiveMeABreak]

Unlikely. The heater system consists of air distribution motors and air mixing motors. It could be several things such as either one of the air mixing motors which as left the mixer on one side in a fixed position. If this is the case it could be either the motor or the spindle / gear from the motor that moves the mixing flap.

Diagbox should be able to confirm whether the specific motor is responding to commands using the appropriate live data parameter. If it is registering the motor movement, then that would indicate that the actual motor is operating, which could then leave the spindle / gear as the fault.

The other possibility is a blocked heater matrix. When this happens it can lead to blocking of one side. To rule this out, try setting the cold A/C to the opposite side with the problem. If that is working and changes back to hot when commanded on the same side, then the matrix is likely OK.

Right Side

Distribution Flap Motor = (4)
Mixing Motor = (6)


Left Side

Distribution Flap Motor = (2)
Mixing Motor = (3)

You can read the following faults with Lexia:

• Absence of communication fault with the built-in Systems Interface
• CAN network fault
• ECU not communicating on the CAN fault
• Air conditioning panel control button fault
• Passenger compartment temperature sensor fault
• Passenger compartment humidity sensor fault
• Evaporator temperature sensor fault
• Left brightness sensor fault
• Right brightness sensor fault
• Passenger compartment temperature sensor rotor jamming fault
• Recycling motor fault
• Front left distribution motor fault
• Front right distribution motor fault
  
• Front left mixing motor fault
• Front right mixing motor fault
• Blower rotor jamming fault
• Blower supply fault
• Blower overheating or excess current fault
• Blower diagnostics signal fault
• Air conditioning ECU internal fault

[Orbit Motors]

Incidentally, I forgot to mention, there is an active fault for the passenger side mixing motor (code C72E), I initially dismissed it as I wasn't sure if that could cause the symptoms I'm experiencing - but maybe it could be that then.

Do you happen to know if they are a pain to change?

Thanks for the insight in to this by the way.

[GiveMeABreak]

So caution here - as sometimes they refer to left / right which makes it easier to know which side they are referring to, but in terms of 'passenger' or 'driver' when it comes to info, it may mean they are talking about the driver's side on a RHD vehicle...

So if this is the case you may be in luck if the actual reduction motor is the culprit. It's quite rare that the motors fail, more often being the internal gear they attach to, which often means a major intervention on the heater assembly itself, as in dash out most likely.

Fingers crossed that as Lexia states it is actually the motor though, which on the UK driver side means you need to disassemble the driver's knee airbag unit to get access.

Parts Diagram showing the motors

So if this is the case, you would be looking at the right side mixing motor in my previous diagram (6) in my previous post, which should equate to motor (2) in this parts diagram below. Part number 6447RJ, £127.44 inc. VAT from Citroen.

[Orbit Motors]

I did suspect that they may be referring to the 'wrong' side if they never altered the criteria from a LHD vehicle, hopefully all this pulls together and is correct.

Really useful information by the way thank you - is it obvious how the airbag unit comes out and any specific caution to take other than the obvious?

[GiveMeABreak]

Obviously position the electronic chair adjustment and steering column up and out the way first if you have electric adjustment on this as you'll have to disconnect the battery first (BSI Reset / Battery Disconnect / Reconnect Procedure) to allow time for the airbag modules to discharge. The only info I have refers to the opposite side so totally irrelevant for RHD vehicles.

But have a look at the side trim panel first and remove that to see what sort of access you have - knowing the French you may not even have to touch the knee airbag despite what I said earlier.