W203 EC light permanently On

[PhilL]

Took a run to London yesterday in my wife's C200K Coupe. On way up air-con seemed to work fine but around Marble Arch noticed EC button was lit and car was getting warm. I thought my wife had switched off, (I like the car cold when driving but passengers often forget their hats and coats) but on setting off for home found I could not switch AC back on; EC button remains lit.

Sweated all the way down the M4 with sun blazing straight into the car.

Investigated today!

Manual says EC will light if gas is low but I topped it up a few weeks ago, so got out the bottle of R134A and gauges. Pressure in system as expected but compressor still will not run.

Checked on Detali.ru to try to identify where the pressure switch is. To my surprise found no mention of pressure switch. Had a rummage around the engine bay (surprising how little room there is under the bonnet, even with a 4-cyl) and found an electrical connection to a 4-way unit at the bottom of the condenser identified on Detali.ru as a temperature sensor. removed, cleaned and refitted the connector, but still EC lit.

No warning lights on but connected my Gendan EOBD with Engine Check software and had a play monitoring live values and graphing various engine paramaters. Didn't help but was fun for a while.

2 hours later and none the wiser, almost called MB Bristol service dept; but thought I would wait until the full power of the forum could be brought to bear on my problem.

So: EC light permanently on, gas in system, no warning lights but no cooling. Any suggestions would be very welcome. Only 2 days before I have to make that call!!!!

 

[BlackC55]

If it has gas in it and It has not leaked out the fault memory will just need erasing.

 

[PhilL]

I did wonder whether it might just need to be reset but I'm not sure if it can be done without Star diagnostics. Would disconnecting battery clear the memory?

 

[nickcc101]

Had same problem when i bought my car, had to go in to MB Exeter to be reset on Star. If i had to pay it would have been local Inde who charges £36 excl vat for Star.

 

[PhilL]

Took the car to local MB to check diagnostics and was told it was low on gas.

Told them I'd checked and there was 3 Bar in the system, questioned whether it could be a sensor not reading correctly.

Told sensors checked OK.

Reluctantly booked in to have re-gas for £80 and delivered Wed am.

Wed pm. call from MB, Condenser leaking and needs replacing.

Told them there was pressure in the system so why would the leaking condenser cause the EC light on.

Told there was no pressure in the system now because they'd taken it all out! should be 750g but only 250g removed, therefore low on gas and condenser still need replacing.

Said I couldn't understand why a small leak would stop it working and were they sure the temp/pressure sensor is OK? besides, It has been leaking since I bought it 2 1/2 years ago and all I've had to do before is give it a squirt.

Told sensors OK and still needed a new condenser.

After a quiet word in my ear from the wife I gave up and agreed to have the new condenser fitted, but were they sure it would fix the problem as I still thought it was a sensor problem. Yes!

Thur pm picked the car up and AC working brilliant! Still could not understand how how it fixed the problem until the following morning when I got under the car and found a brand new Temerature/Pressure sensor fitted in the bottom of the condenser! - but not listed on the bill.

Maybe the sensor comes as part of a new condenser!

Anyway, the wife is very happy and it only cost me £600!

 

[lynall]

3 bar sounds low, iirc between 4 and 6 bar is right.

Here item 20 http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=203245&M=111%2E955&GA=722%2E616&GM=716%2E622716%2E627716%2E630&CT=F&cat=69J&SID=83&SGR=195&SGN=07


Lynall

 

[PhilL]

The 3 bar measured is the static pressure without the engine running or comperssor engaged. Under these conditions, and with an ambient temperature of 10 DegC the pressure of R134A should be 313 kPa (3.1 bar). If the engine and compressor were running the pressures would be very different but a pressure of 3 bar should not prevent the compressor from engaging.

 

[lynall]

Machine at work pressure between 4 and 6 bar before the engine started



Lynall

 

[BlackC55]

The AC working pressure at full yield is 10-12Bar.

£600 is far too much for this repair.

Condensers are very common to leak on MB's.

 

[kwakdonut]

The AC working pressure at full yield is 10-12Bar.

£600 is far too much for this repair.

Condensers are very common to leak on MB's.

You're right, a common problem but £600 seems to be about the going rate. Had mind changed last year at my local indie and cost about the same

 

[lynall]

Almost the first job i had to do on mine one of many, cost about £90 ish iirc.

Didnt know the pressure went to 10 plus bar when running, but to be honest i have never left the gauges connected when engine on.


Lynall