KitsonSD3
Member Since: 05 Jan 2024
Location: Southampton
Posts: 3
  
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| Aircon stopped and heated mirrors on! |
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Hi All,
I'm hoping someone with some technical knowledge of the ATCM system might be able to point me in the right direction.
I have a 2006 (56) Disco 3 HSE with rear AC. It hasn't worked since I bought the car at the end of last year, and I recently decided we needed it, so went and got it regassed. The guys said it held vac for 20+ mins no problem, they refilled it with refrigerant and it ran ice cold. Perfect. This continued for around a week, lovely cold air from all vents, front and rear. Until yesterday, when my wife went out and the AC was blowing warm. I've tried a couple of times now and get the same, warm air with AC on and set to cold/auto. If I press Econ, it chills slightly, but only feels like fan chill, not AC chill.
Plugged in my GAP iid and it's showing pressure, and showing current to the compressor. However in the HVAC area, there was a field called 'External ambient air temperature' which was either showing N/A or -36c (it was a warm afternoon). the dash was showing 19c which was about right.
I noticed at the time I found this that the door mirror glass was very hot too, so I am wondering if possibly some sensor is telling the car that it's freezing cold outside, so the mirrors are switched on automatically and it won't fire the AC? Any idea which sensor this would be, as I assume it isnt the normal air sensor on the front bumper if the dash readout is displaying ok?
Are there any fuses/relays I can check before I bother taking it back to the garage? the blowers all work, just no cold air!
Thanks in advance.
Simon
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 11th Jul 2024 8:25 am |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10731
 
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the dash temperature display has massive damping/delay on it. I think this has an impact, but can't remember what.
Therefore the sensor could be doing all sorts of wild things and the climate could be seeing it.
Probably worth having a look or replacing the sensor somewhere behind the front bumper.
Be worth checking the A/C after 2 hot days in a row, having turned the ignition on, on both days.
With the red light lit on the ECO button, the A/C is off.
Try setting the temp to 17 or Lo
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| 11th Jul 2024 8:45 am |
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KitsonSD3
Member Since: 05 Jan 2024
Location: Southampton
Posts: 3
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Hi
thanks for the info. so is there just the one external temp sensor on the car which is utilised by multiple systems then? I'll look at getting a replacement of this sensor.
I don't have any light on the Eco button (other than when I breifly had it on to see if this changed anything) I had A/C on with it in Auto and tried putting both dials in the front, and the one in the back on their lowest setting on the dial, but just got hot air from the vents.
I'm suspecting the A/C fault isnt due to anything like a leak in the A/C or the compressor as it ran perfectly following the regas for a while, and I'm getting the odd -36c reading on GAP along with the mirror, so I think something like a fuse/relay or this temp sensor is more likely the cause, but I am not sure which fuses/relays are linked to A/C ATCM functions.
Took the car out again today and the dash was reading 23c (5 degrees hotter than it read yesterday, and seems about right for today). A?C still blowing hot. I tried the Econ+Recir button test and all came back ok. tried running the AC hot for a few mins and then back to cold, still blowing hot air out.
When I got home, the top of the FBH was red hot when I opened the bonnet, so I suspect that's been running too.
thanks
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| 11th Jul 2024 8:59 am |
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M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8243
 
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Take fuse out to the FBH and see if that helps, also if the FBH comes on something is telling the system it is cold outside(freezing?) this may be the cause of the aircon not working.
With the bonnet up engine running at tick over you should be able to hear the ac compressor kick in. It can when others can't,
It will when others won't,
It goes where others don't.
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| 11th Jul 2024 3:37 pm |
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