Intermittent aircon

Stratman

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Please forgive a first-time poster if this is the wrong forum, but I do suspect the electrics side of the system.

My C180 has developed a fault with the aircon. First drive of the day it doesn't work, in that the electromagnetic clutch doesn't engage. Leave the car for maybe half an hour and then it will work perfectly. I have taken it to a specialist, but of course it works when I get there, so they can't really do mich except confirm that there is the correct amount of R134 in the system. I have checked (and swapped) fuses 2 and 12. The red LED on the EC switch goes out when I switch the aircon on whether it works or not. The Haynes manual is next to useless on both aircon and wiring diagrams. Any ideas?

Blowing hot and cold

DD
 

Sp!ke

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Could it be that the interior sensor is not sensing the temperature correctly?

I dont know about your C180 but on or later 201, 124 and 126 cars, the inside air sensor is located next to the overhead courtesy light behind a small grill. On these models at least, there is a air tube leading from here to the sensor which can perish or be dislodged and cause similar symptoms.

There is also a small fan attached to one end of this grill. Turn your blower to high, and blow some smoke at the grill and check if it is drawn into the grill. If no air flow is present, the hose could be damaged or the fan could have died, thus causing erratic temperature variations.

Its a two minute test so probably worth eliminating.
 

DavidG

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Apr 25, 2003
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C220 CDI (1999)
To Stratman

Hi

My C220 CDI 99 has developed the same prob, very irritating when you go to your dealer to be told that "it is working, come to see us when it is not"!

Any luck on your side?

David
 

jimmy

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Originally posted by Sp!ke
There is also a small fan attached to one end of this grill. Turn your blower to high, and blow some smoke at the grill and check if it is drawn into the grill. If no air flow is present, the hose could be damaged or the fan could have died, thus causing erratic temperature variations.

Its a two minute test so probably worth eliminating.

Or if you dont smoke use a small piece of tissue paper, it should stick to the grill if the fan is working.
 

GRAV888

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2017 CLA 180 AMG in Black (mine) 2018 GLA 200 SE in Black (wifes)
As the other members of the German GTG will tell you, my c180 developed exactly the same problem in Germany.
Rather frustrating when you're cruising along the autobahn at 100+ mph in sweltering heat.:crazy:
Taking it to the stealers tomorrow to try and sort out. (Along with a new radiator and a wheel bearing that started off as a quiet droning on saturday, but has now blown itself apart).:mad:
I'm just thankful that I made it back to the uk before it went totally.
Will report back if I have any luck with the air-con, although I doubt it, as I'm taking it to Medway Mercedes.

P.S.
G GTG pics will be posted soon.:bannana:
 
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Stratman

Stratman

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Thanks for the replies gents (and ladies?). It's frustrating, as when it works it works extremely well. When I get a chance I'll try to trace the wiring as mine is an older car without climate control, so it shouldn't (ho ho) be too difficult. I just wonder how many switches and sensors there are in series.
DD
 

Sp!ke

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Even the cars *without* climate have the same temperature sensor and intake. Same test applies.
 

DavidG

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C220 CDI (1999)
hi all

For some reason, I started my engine earlier today and pressed/ hold the aircon button and the recycle button together for a few seconds, the recycle light came up and flashed for a few seconds.

Any idea what that was?
 

Brian WH

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Originally posted by DavidG
hi all

For some reason, I started my engine earlier today and pressed/ hold the aircon button and the recycle button together for a few seconds, the recycle light came up and flashed for a few seconds.

Any idea what that was?

Looks as if you had "Confused the system".:confused:
 

Simon

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Mark,

Cheers, there's a lot if info on that site. I've made enquiries with them about getting mine serviced. There's nothing wrong with it though, but I want to keep it that way.
 

DavidG

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C220 CDI (1999)
Hi Stratman

I've just opened a new subject ( £1.000.000) about the following:
-----------------------------
The AC compressor on my C220 CDI only kicks in when the engine has reached its normal temp. Only then, can I switch the engine off and on again and it works normally. Engine cold and it's all over again.

Suggestion leading to a repair will be rewarded.

Cheers
----------------------------

Maybe yours do the same after all.
 
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Stratman

Stratman

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That sounds very like the way mine behaves. It seems that something needs to be hot before the A/C will engage. If I do a short (say 5 minute) drive from cold, the cooling will not work, but if I just switch off and leave it for about a quarter to half an hour, then it will. I can only assume that the heat generated by the short journey is permeating through the engine block and heating up something. The big question is, of course, what? :confused:
 

DavidG

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C220 CDI (1999)
I was told yesterday that somehow the system is limit low on gas and that when the car is warm, the gas in the pipes and the condensor has been warmed just enough to bring it above the shut off point.

It is a bit of a long shot but are you sure your aircon is full?

By the way do you know where is that little window through wich you can check your aircon level when it runs? Cause I can't check my level.
 

Shude

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Hmm, my aircon went crazy about 2 months ago and I've not had it looked at yet. Mine does some of the things listed on this thread, with the exception that mine doesn't cool the air down any more, it heats it up a LOT :(
 

jimmy

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Originally posted by DavidG
I was told yesterday that somehow the system is limit low on gas and that when the car is warm, the gas in the pipes and the condensor has been warmed just enough to bring it above the shut off point.

It is a bit of a long shot but are you sure your aircon is full?

By the way do you know where is that little window through wich you can check your aircon level when it runs? Cause I can't check my level.

That sounds possible to me.

The window is on top of the dryer/receiver mounted in the LH fron wing just to the bottom side of the radiator. The window shows that there is lubricant in the system and that it is being pumped around, it is not an indicator of the gas level. Best to get the syatem re-charged.
 
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Stratman

Stratman

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When I first noticed the problem I took the car to an A/C specialist and of course on arrival it was hot enough (or had been running long enough?) for the system to work. The only thing they could do was put their wondrous machine on the compressor, which indicated that all pressures were OK. This,they said, meant that there was the correct amount of R134a present. They were most helpful, but basically (and understandably) said "Bring it back when it's broke"
I did notice that when the engine is cold, there is liquid in the sight glass, but when it is hot and the A/C is running, there is nothing visible. They (VACS in Byfleet) said that this is normal as the R134a 'gasifies' when the cooling is operating.
Incidently, I drove to work this morning and the A/C did not engage at the end of an hour's drive. Eleven hours later, the car having been parked in full sun all day (and on a fair slope.....hmmm) the cooling kicked in as soon as the engine was running.
 

DavidG

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I was told somthing about a pressure switch on the evaporator or a thermostat.........
 

Andy W

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As a new member to this board and been experienced in car air conditioning I may be able to offer the following. First of all my C180 does not arrive until next Friday so I do not know the exact make up or layout of the Merc air cond system but generally the following may help.

Refrigerant gas is pressure temperature related the colder the temperature the lower the pressure, the higher the temperature the higher the pressure, ok so far, obviously when the system and engine is cold no heat is transferred to the gas resulting in a low pressure condition, a car with climate control should be able to call for air cond to demist windows etc on a cold day, various components can prevent a system from running for example on Vauxhalls a sensor is fitted so if the outside ambient temperature is too low the system can not run, some cars have a thermistor attached to the evaporator coil, (cooling matrix) called a frost stat, if the temperature is too cold say 0oC the system will not cycle, the favourite though would be the low presssure switch or low gas switch, the low gas is fitted to some cars in the high pressure liquid gas line after the filter drier sometimes right next to a high pressure/fan switch, the low pressure switch is fitted in the large suction pipe which carries vapour gas between the compressor and the bulk head of the car where the pipe work exits, the easy cheapest way would be to remove the refrigerant from the system, dehydrate it and weigh in a fresh liquid charge. A easy way to check a system would be to warm the car up to make the a/c run first, get an assistant to hold the revs at 2000rpm and observe the sight glass in the top of the filter drier, you should see nothing until the system stops which you will hear by the magnetic clutch clicking and the rpm rising, while the sight glass is clear and the system is on the large suction gas pipe going back to the compressor should be cold on any of the steel or alloy hose fittings. If this is all ok the problem is more likely to be a faulty switch or sensor/thermistor or even a damper. It does not cost much for a proper recharge. I hope the above helps and that you can understand what I say, its easy for me because I can visualise the functioning system in my mind.
 
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