2012 E-Class Aircon Problem

[E55BOF]

The aircon on my 2012 E63 is playing up. I topped it up a couple of months ago, and it's not giving the three flashes of the red light that you get when the compressor shuts down because there is insufficient refrigerant, but the passenger side and rear air outputs are being heated even with all the temperatures set to Lo(w). It's taking a long time before the driver's side cools much as well, but the air does come through cool eventually.

I've had the iCarsoft on it, and there are no fault codes. The running data shows that the flap motors for both front sides are in exactly the same positions, so I presume it will turn out to be a mechanical problem with one or more of the flaps come adrift or broken a pivot. It's going in to Terry Gates on Wednesday, and I'm certain he'll sort it out - at a cost.

One question, though. The running pressure in the system is around 10 bar. Does anybody know whether that's about right, or on the low or high side?

 

[Gbrowncls55]

If it worked properly after you had it professionally (i assume) recharged then you are losing refrigerant somewhere. They are all the usual symptoms.

 

[alabbasi]

Put a set of gauges on it and let us know what the pressures are on the high and low side. Without this, no one is going to be able to tell you anything about what's going on with it.

 

[E55BOF]

If it worked properly after you had it professionally (i assume) recharged then you are losing refrigerant somewhere. They are all the usual symptoms.

So low refrigerant can cause the system to blow cold on one side of the car and hot on the other side? I've never heard of that before on a W212; any idea how it does it? It would be nice if you were right, though - and cheaper to fix...

 

[alabbasi]

So low refrigerant can cause the system to blow cold on one side of the car and hot on the other side? I've never heard of that before on a W212; any idea how it does it? It would be nice if you were right, though - and cheaper to fix...

It would do exactly that on a W210.

 

[E55BOF]

Thank you for that. Yes, I know; I found plenty of info on that exact problem on the W210, and on the W203, but not on anything later. The 212 doesn't have the detailed built-in aircon OBD system of the 210, though the data is probably there to be read with a Star, but I've gone as far as I can with the iCarsoft and it found no faults. If I'd known what the normal running pressure was, I'd have known whether 10 bar was OK; but I didn't. so I didn't...

HOWEVER... The system had shut down soon after I got the car, so I knew there was some kind of leak, which has not been fixed, just topped up pro tem, so perhaps the W212 could do that, and it was just low refrigerant? I shut off all the airflow to the passenger side and rear, set everything to Lo(w), and started the car. The driver's side was now getting the benefit of whatever cooling effect there was, and was definitely being cooled, but didn't seem to be cooled by very much. Hmmmm.....

250 gm of refrigerant later, and Bingo! normal function restored. Time to get it fixed properly, then.

So now we know; uneven air conditioning cooling on a W212 can indicate a low refrigerant level, even when it's not low enough to cause the system to shut off automatically.

 

[Gbrowncls55]

Yes cool on one side and warm on the other. That is exactly what my CLS did before it was re-gassed two weeks ago. Now icy cold on both sides again. As with mine it probably points to a leak somewhere. Mine took a year to lose its refrigerant/ cooling ability last time. Probably needs a new condenser which they will check at the next service. The bigger the leak the quicker you lose the cooling...obviously.

 

[E55BOF]

I know it has a leak, though it wasn't empty of gas when I got it. I topped it up myself both times, but time now to get it fixed. I'll take it to an excellent local aircon specialist I know - Vanchilla in Cookham - to sort it out, but I expect it will be the condenser; it almost always is.

 

[Gav78]

Sounds like you need a new header blower regulator. I had this problem on one of my previous cars (passenger side blowing hot air) and that was the culprit

 

[OneForTheRoad]

after a regas my mb2 said 4 bar . hth .

 

[stephenmercedes]

I know it has a leak, though it wasn't empty of gas when I got it. I topped it up myself both times, but time now to get it fixed. I'll take it to an excellent local aircon specialist I know - Vanchilla in Cookham - to sort it out, but I expect it will be the condenser; it almost always is.

Make sure you report back here when you get it fixed with what the the fault was & cost - gives the next guy with the same problem a fighting chance to get an answer

 

[E55BOF]

It will cost about £200 all-in to replace the condenser and have the system recharged (I have about 1 kg of R134a already), which is almost certainly what will be needed. A decent aftermarket condenser, probably a Nissens, costs about £100-120 on eBay.

 

[stephenmercedes]

That sounds like a plan! The condenser I got for my old W203 was a 'Hella' one and cost me £65 inc P&P! Best of luck with the result...

 

[mcshape]

Shot in the dark here - Had a similar problem in a 2010 W212, Turned out the temperature sensor in the passenger footwell was damaged and was misreading the car internal temperature for that side, sensor replaced and VOILA! Icy cold everywhere!