BOTUS

nov 2006 W221 S500

the passenger (left front) air con isn't working at times. After a 1 hour drive it started to work correctly and remained like that even after it was switched it off for more than 30 mins. Next day out its off again.

I believe until recently it was working as expected, heater control works fine, (ambient and heating work as expected) but no cooling on one side of the car, all the vents and controls work fine, no error codes, ac diagnostic check reports all OK.

Is this a common fault ?

I see after the telematics update (that it hasn't had yet) often the AC plays up. In what way does it "not work"?

Searching posts about telematics update problems, AC issues are related to SAM module needing a kick. Other known issues could be rear camera and ipod interface. Perhaps connected? both have just been retrofitted to this car.

"If experienced after Telematics update front SAM needs recoding
(SAM = Signal Acquisition and Activation Module (110 in diagram) controls various functions. )"

BOTUS

dam... I edited (overwrote my post) it was around this....


so I noticed AC gas was very low, so I added a bit I had left lying about, after I did this front AC seems to work again, rear still a bit naff. Next day with new bottle added quite a bit more and got


LF 1.5C about 36F
RF 2.0C
LR 12C about 56F
RR 14C

BOTUS

maybe coz I was on the spanners once and knew how to do it or maybe the last 3 profexxxxxx idiots that worked on cars with air con I know messed them all up, I'd rather refill my AC than them.

Trouble is I don't have the full kit... anyway I see under the bonnet (hood) the ones with rear AC take 200g more gas, (and 1.8 Ltr more engine coolant for heating) so it must be all one upgraded system. With rear AC it should have 1180g of r134a.

If it had never been topped up and lost about 5% a year, I think it needs about 400g of gas. Being lazy / not paying attention as it was struggling to get above 20PSI, I ended up adding 500g that's what got me the figures above in the rear.

So I let a bit out next day, but from pressures I had, ambient temp at the time and where I ended up, I decided to play in excel and I came to conclusion I should have added more. Now rear AC is pathetic at 16 and 18C (not sure why right side is lower. Before I added any gas it was the right side that was cold).

I think I was being conservative at 5% a year loss, seems 10% is expected and up to 15% allowable

At 10% loss a year (with the bit I took out) I still need to add another 200 to 300g ... which might be enough for the back to come to life...


Thanks for all the help far