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Interior Demisting Conundrum
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Author Post
keithc   
Wed Dec 07 2016, 04:23pm
Joined: Apr 03 2016
Member No: #2584
Location: Kildare
 My C6 was fogging up something chronic on the way home from work a few times the last few weeks.

I have eventually figured out, after putting in a new pollen filter to no advantage, that as soon as the exterior temp goes to 5 C or less the windows will fog up almost instantly. All I can think of is that the air con stops working or something.

I have tried it on Auto, have the Window demist button on, or have the control pointed to the window and all will be fine (even if fan is at no 1 speed) but as soon as the temp drops to 5 all hell breaks loose and the car fogs up!

I end up putting temp up to max, hit the window demist buttons, put the fan speed to max and open the sunroof on tilt. When the windows have cleared I put the heater to feet and window, have the speed to one over halfway and keep the sunroof tilted and it does a good job of keeping the windows clear.

But if I was to reduce the speed of the fan it'll fog up. I go into the air con settings and air con is on but all I can think of it's being triggered off when the temp hits 5 or below. (At 6 or above the windows will be kept clear even at a low fan speed).

Anyone ever hear of this or any idea on what I should or could do?
JPV   
Wed Dec 07 2016, 04:35pm
Joined: Sep 04 2011
Member No: #606
Location: Norwich
 Are you sure you haven't got it on recirculate rather than external air. This would give the result you report.
keithc   
Wed Dec 07 2016, 10:41pm
Joined: Apr 03 2016
Member No: #2584
Location: Kildare
 Ya, it has fresh air coming in at all times. Forgot to include that in op. Like I say it only happens when the display shows the external temp to be 5C or less. At 6C the system is working fine, temp goes down to 5C and then the windows start fogging. Very unusual!
Norman   
Thu Dec 08 2016, 10:59am
Joined: Feb 06 2011
Member No: #364
Location: Huddersfield and Torremolinos Spain
 Went down to to autotronics on monday temp varied from 5 degrees to -2 and had no problems whatsoever and with no aircon turned on and all settings at default.
onthecut   
Fri Dec 09 2016, 10:39am
Joined: Sep 20 2016
Member No: #2793
Location: West Mids
 Hi Keith.

Have you checked the coolant level in the expansion bottle ? If it's down, your misting up symptom might indicate a leak somewhere around the heater matrix, so that the air passing over it is picking up excess moisture.
Likewise, I'd also have a feel under the carpets for damp. Those frameless windows look like prime leak territory to me.

Mike.
David Hallworth   
Fri Dec 09 2016, 11:16pm

Joined: Apr 16 2010
Member No: #90
Location: Glasgow
 The other thing to check is that the air con compressor is kicking in, if it's not that can cause a car to fog up and become a [%*^#@!] to demist.

In the 407 if we got in it with damp jackets it would mist up and would take an awful lot to demist, since I replaced the condenser and had it regassed it demists very quickly and will stay clear.

Just because the HEVAC system says the A/C is on, it doesn't mean it's actually engaging the compressor, if it's short of gas the compressor won't engage.

David.
cruiserphil   
Sat Dec 10 2016, 11:59am

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
 Keith,

Onthecut's suggestion of a leak at the heater matrix or a hose to it is one worth checking. Also below a certain outside temperature the air con should not operate to protect compressor lubrication. I don't know what the threshold is for the C6 but it.sounds from your description that it is at 5degC. In other words, the air con is handling the moisture but at 5degC and below the air con switches off and then the moisture can enter the cabin and condense on the cold glass.

Best regards,

Phil C.
eduardomaio   
Sun Dec 11 2016, 03:46pm
Joined: Apr 18 2012
Member No: #869
Location: Lisbon
 I'm sure the compressor works at 5ยบ C and below. I have been with the C6 in below zero temps and the aircon was working ok.

I would first check if the aircon has enough gas. It's cheap to do.
Website
keithc   
Sun Dec 18 2016, 12:02am
Joined: Apr 03 2016
Member No: #2584
Location: Kildare
 I've found the below after figuring out the car is going into air recirculating mode once it hits 5 deg or less. What I am taking from the below is that I could have a faulty air quality sensor and it's causing the fresh air flap to close at 5 deg or less? Or what are others reading on what could be happening? I've no loss of coolant etc. It's just once the outside temp reaches 5 deg or less I have fogging of the windows and I now press on button 7 in the pic below to manually open the fresh air flap and once the windows are clear I can put the fan speed to 1 or 2 and it keeps the cabin from fogging even below 5 deg.
 

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