C4 Split Cabin Heating

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gosnoid72
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C4 Split Cabin Heating

Post by gosnoid72 »

I have a 54 plate C4 VTS with split cabin heating (not sure if that's a standard thing). Today when driving home with the engine warm I had both sides set to low and the AUTO and A/C set to off. The temperature coming out of the vents above the stereo were completely different (very cool from the driver's side and very warm from the passenger side) Any ideas?
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GiveMeABreak
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Re: C4 Split Cabin Heating

Post by GiveMeABreak »

Heater matrix / blockage or broken air mixing module gears on the air distribution or air mixing flap reduction motors.

You'd have to do some testing to see which by adjusting left and right side direction and and see the reaction, then the same for the temperature adjustment to help determine.
gosnoid72
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Re: C4 Split Cabin Heating

Post by gosnoid72 »

Thanks Marc, can you explain what you mean by left and right side direction adjustment? Is it a case of centre console out to gain access to the matrix?
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GiveMeABreak
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Re: C4 Split Cabin Heating

Post by GiveMeABreak »

Pop your VIN up for me so I can see which system you have.
gosnoid72
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Re: C4 Split Cabin Heating

Post by gosnoid72 »

Will do. Just need to locate it!
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GiveMeABreak
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Re: C4 Split Cabin Heating

Post by GiveMeABreak »

Outside lower portion of the passenger side windscreen in a cut out.
gosnoid72
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Re: C4 Split Cabin Heating

Post by gosnoid72 »

Thanks - VF7**************[VIN obfuscated, can be read by forum staff]
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GiveMeABreak
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Re: C4 Split Cabin Heating

Post by GiveMeABreak »

Ok so you have the automatic bi-zone Air Conditioning system (with digital control panel). So what I was suggesting was to test the system out for temperature changes on each side and for air distribution on each side.

You need to get the car to operating temperature, then turn the A/C on with the engine running. Check the left and right side separately. Change the temperature to max heat and cycle the air distribution settings (screen, face, floor) and listen to see if you can hear the motors change the flaps inside the unit - check that the air moves to each of the the desired locations, but bear in mind it can take a few seconds for the motors to respond. Then change the temperature to the lowest setting and repeat, going from one air distribution setting to another.

Repeat this for the other side so you can determine if it is a motor distribution issue where the motor is not a) changing the air flow direction or b) bit mixing the air temperature on one side.

If the air motors seem to be operating ok, then you may well have a blocked heater matrix, which may need flushing through.
gosnoid72
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Re: C4 Split Cabin Heating

Post by gosnoid72 »

Thanks. Another job for the weekend then!
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GiveMeABreak
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Re: C4 Split Cabin Heating

Post by GiveMeABreak »

Your sort of just trying to understand whether it is one of the motors that has failed or the gearing that operates the mixing flap which may have worn, or whether you need to get somebody to backflush the matrix for you and see if that unclogs it.

Sometimes this can be done with a hosepipe and use of the pipes as they enter the bulkhead from the engine compartment.

Maybe worth a watch:

gosnoid72
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Re: C4 Split Cabin Heating

Post by gosnoid72 »

Ok, got round to it tonight. To summarise, the driver's side behaves exactly as it should. the temperature adjusts, as set on the control and the direction of flow likewise. On the passenger side, the direction of flow responds correctly, but the temperature remains warm, regardless of the setting on the dial or the activation of the a/c.
gosnoid72
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Re: C4 Split Cabin Heating

Post by gosnoid72 »

Update - today I listened as I adjusted the temperature dials. On both occasions I could hear the motor working, but the passenger side one sounded distinctly different and had no effect on the temperature, so I'm thinking possible dodgy motor or gearing.......