Aircon problem

Author
Discussion

lowdrag

Original Poster:

13,021 posts

218 months

Tuesday 23rd July 2019
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Driving home three weeks ago the aircon failed, so I turned it off. Ten miles later I tried it again and it worked fine. The car is a 2012 T204 by the way. Since it is seven years old I had it regassed a week ago and things were fine - until today. Suddenly, on arriving at my destination, it failed again. Get in the car 30 mins later and it was working, but not flat out if you know what I mean. Park it up again for 15 minutes, and the trip home was fine, the system working as it should. Any ideas?

WJNB

2,637 posts

166 months

Tuesday 23rd July 2019
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A leak somewhere. Secure the services of a mobile A/C technician who most likely will fix it on your drive or get the parts & fix it. Wife's Juke fixed for £150 including a new pipe. (2015)
Or seek out an independent Mercedes specialist but under no circumstances take it near a Mercedes main dealer you will be robbed.
I know because I've been there & was able to avoid being robbed after being given a stupid quote to have A/C fixed. On a 2012 SLK the entire A/C system replaced at half the main dealer price by a superb specialist with an international reputation & client list. (Worthing south coast).
30+ degrees today & I got very cold.

lowdrag

Original Poster:

13,021 posts

218 months

Tuesday 23rd July 2019
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Thanks for that; confirms my suspicions. It would happen when the temperature hit 42C this afternoon too!

stevemcs

8,923 posts

98 months

Tuesday 23rd July 2019
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I take it they pressure tested it and it held pressure for a reasonable amount of time ? If it works and then stops and then works then its unlikely to be the gas, more likely the compressor.

lowdrag

Original Poster:

13,021 posts

218 months

Wednesday 24th July 2019
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Steve, I was fearing that. I had to change the compressor in the last car, a T202, and that was pretty expensive. But I hear that the compressors are made in the USA and badged with the Mercedes name so it might be far cheaper to research that and see. So I stopped typing and did a quick search. The Denso one (a very reliable make usually) is quite dear but the Valeo (big in Europe) is about £250. So far cheaper than 10 years back it seems. As aforesaid, the system was recharged only last week and works fine - when it works, so it can't be a loss of gas and that only leaves the compressor really.

noodleman

827 posts

218 months

Wednesday 24th July 2019
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I had similar on my 204 c63 very recently. Turned out to be the compressor and cost £780 at the main dealer. Ouch. But I wouldn’t want anyone other than Merc to work on this engine; I think some drive belts have to come off to even get to the compressor...

lowdrag

Original Poster:

13,021 posts

218 months

Wednesday 24th July 2019
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I fully understand noodleman, but I have some pretty efficient mechanics here and my car has not seen the inside of a dealership except for the first year while under guarantee (I bought used). The last service a year ago was telling. The parts cost alone at Mercedes was €200 for the diesel filter, then with all the other filters and oil and labour it came to €1,200. My garage buys the same parts (Bosch) and as an example the diesel filter was €40. I paid €450 all in. Mercedes here charge €120 ex VAT per hour.

Sheepshanks

34,302 posts

124 months

Wednesday 24th July 2019
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Some thoughts:

I'd have expected (but I could be wrong) that these variable displacement (swash plate) compressors would either work or they wouldn't. I suppose it's possible that whatever moves the swash plate is working intermittantly but it seems just as likely that whatever control device (temp sensor, ECU etc) tells it to move could be faulty.

My thought would be that it could do with someone checking the compressor is getting the correct level of signal to tell it how much cooling to provide.

I don't know how much the Mercedes tool, StarDiagnose, tells mechanics but ideally you could do with finding an indie/specialist with it who also understands a/c systems (I imagine the latter shouldn't be too hard in France).


The a/c in my 2005 C Class estate, which I've owned since it was 5mths old, has always been marginal. Dealers and indies have looked at it, but it's never changed - it works, but it's just not 'properly' cold. Someone on a forum the other day asked if the expansion valve had ever been changed - on Googling it seems like it's a real possibility for my issue, and it's a cheap and easy swap, but none of the people who looked at the car have mentioned it before.

stevemcs

8,923 posts

98 months

Wednesday 24th July 2019
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Its common on the Volvo's where the magnet on the clutch isn't strong enough to engage/disengage the clutch, so it gives a similar effect to what the OP is having. Denso would be OEM but there are pattern parts available. A pattern part fitted to a W204 is around £410. The thermo expansion valve sometimes fails too but it buried at the back behind the scuttle.

It might be worth trying this too.

https://itstillruns.com/reset-mercedes-ac-system-7...

lowdrag

Original Poster:

13,021 posts

218 months

Wednesday 24th July 2019
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Doesn't seem to work on the W204 sadly.