Heating & Air Con issues on W220 S CDi 2004
06-10-2013, 06:27 AM
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S320 cdi 2004
Heating & Air Con issues on W220 S CDi 2004
Hi All,
The climate system on my S320 CDi (2004 SWB) is playing up. Main problem seems to be lack of any decent heat, and despite settings to "HI" only gets up to about 23c. I've checked the readings on the error faults menu on the AC as I did have a red light on the AC button with a corresponding 1256 code (evaporator sensor), but that was cleared and then started to blow cold air fine.
I did a 6 mile run out in it and it continued ok and after30 mins no more errors displayed on the error menu. (Rest/Charcoal for 10 secs+)
Looking through the report codes (Rest for 10 secs+), both internal sensors in AAC and OHP seem to be reading ok at about 20c, and there's 14 bar of Refrigerant pressure, however the outside sensor ( #2) and refrigerant in car sensor (#8) were reading 43C!! The dashboard temperature indicator was saying 11c which was about what it was, certainly not 43C.
The fan does speed up and down and I can hear actuator flaps moving etc, but it's certainly not behaviing as it should. It's had a couple of visits to the my local main dealer and they have had £600 of my money on a new SAM unit to sort some light issues out and it's also had a couple of regasses with them and with a local AC shop.
Registered 2004, 90K on clock. Im 2nd owner from 2006 onwards. Previously a main dealer demonstrator.
So do I surmise that both the outside temp sensor and refrigerant in car sensor are duff? is the latter the same as the evap temp sensor which triggers the 1256 error? or is that the same as the evap core sensor (item #5 on the list) My evap core sensor was reading 1.9c so I assumed that was ok as its rather chilly.
Blower voltage was 1.9V. all the other parameters around engine revs, ground speed, dew point etc all seemed broadly aligned with reality.
I have look through all the excellent tomes on here and hence why I've been able to diagnose to this point so thanks to all the wizards and bright folks who've helped me no end so far.
As for replacing the two sensors reporting 43C, is that an easy/cheap job for an independent if I point them that way and are the bits relatively cheap or is it a strip the car to the bones job?
thanks for any pointers and building a hugely useful resource
Dr. Jim Cowburn
The climate system on my S320 CDi (2004 SWB) is playing up. Main problem seems to be lack of any decent heat, and despite settings to "HI" only gets up to about 23c. I've checked the readings on the error faults menu on the AC as I did have a red light on the AC button with a corresponding 1256 code (evaporator sensor), but that was cleared and then started to blow cold air fine.
I did a 6 mile run out in it and it continued ok and after30 mins no more errors displayed on the error menu. (Rest/Charcoal for 10 secs+)
Looking through the report codes (Rest for 10 secs+), both internal sensors in AAC and OHP seem to be reading ok at about 20c, and there's 14 bar of Refrigerant pressure, however the outside sensor ( #2) and refrigerant in car sensor (#8) were reading 43C!! The dashboard temperature indicator was saying 11c which was about what it was, certainly not 43C.
The fan does speed up and down and I can hear actuator flaps moving etc, but it's certainly not behaviing as it should. It's had a couple of visits to the my local main dealer and they have had £600 of my money on a new SAM unit to sort some light issues out and it's also had a couple of regasses with them and with a local AC shop.
Registered 2004, 90K on clock. Im 2nd owner from 2006 onwards. Previously a main dealer demonstrator.
So do I surmise that both the outside temp sensor and refrigerant in car sensor are duff? is the latter the same as the evap temp sensor which triggers the 1256 error? or is that the same as the evap core sensor (item #5 on the list) My evap core sensor was reading 1.9c so I assumed that was ok as its rather chilly.
Blower voltage was 1.9V. all the other parameters around engine revs, ground speed, dew point etc all seemed broadly aligned with reality.
I have look through all the excellent tomes on here and hence why I've been able to diagnose to this point so thanks to all the wizards and bright folks who've helped me no end so far.
As for replacing the two sensors reporting 43C, is that an easy/cheap job for an independent if I point them that way and are the bits relatively cheap or is it a strip the car to the bones job?
thanks for any pointers and building a hugely useful resource
Dr. Jim Cowburn
