Air Con blowing hot & cold W203

[miro]

If you are referring to my comment about a single exchanger, I meant how could a problem in the mono valve make one side hot? Perhaps after all the same as the claim on the refrigerant, which I did not understand either.

The flap issues as referred previously would sound absolutely logical but the reset at least did not seem to help on this car.

The evaporator always makes some "hissing noise" as its job is to evaporate the liquid from the compressor but I assume this time the noise is significantly stronger than normal. Could low refrigerant also increase the noise?

I would assume a hissing noise from a leak being quite short in time, if it was leaking so much that one could hear it, it should not have 134a for too long time then, would it?

The heater element and cooler element in the W203 crosses both sides. There is a divide in the middle of the assembly with flaps for the left and flaps for the right.

 

[BlackC55]

I recently did a mad thing and converted 580 into 581 on my car. I notice the blend flap is in fact 3 flaps driven by one motor. There is an extensive set of cogs and wheels held together in place with several screws. It sits vertically on both sides of the heater box.

I also saw that it has liberal amounts of long-life grease on the friction surfaces of the more complex cogs.

So my questions is ..... what do people usually when faced with a stuck motor. How do you service this area in a workshop environment ?

I learned a lot about this assembly by tinkering with my own heater box on a table. But I imagine that most workshops work on the problem in-situ.

To get to some of the motors the dash has to be removed and the heater box also. (~11 hours R&R)

If we can avoid removing it we do. The only time they get to be worked on is when they go wrong.

 

[DansSlk]

If you are referring to my comment about a single exchanger, I meant how could a problem in the mono valve make one side hot? Perhaps after all the same as the claim on the refrigerant, which I did not understand either.

The flap issues as referred previously would sound absolutely logical but the reset at least did not seem to help on this car.

The evaporator always makes some "hissing noise" as its job is to evaporate the liquid from the compressor but I assume this time the noise is significantly stronger than normal. Could low refrigerant also increase the noise?

I would assume a hissing noise from a leak being quite short in time, if it was leaking so much that one could hear it, it should not have 134a for too long time then, would it?

Sorry mate was not referring to you.

It was in reply to Dieselman i was just saying its a single control valve not a duovalve but i am just in the habit of calling it that.

I was in error

 

[miro]

To get to some of the motors the dash has to be removed and the heater box also. (~11 hours R&R)

If we can avoid removing it we do. The only time they get to be worked on is when they go wrong.

11 hours ? That must be some kind of official billing thing.

 

[Barticus_UK]

Hi again, a quick update. Found THIS whilst trawling the forum. It explains how to put the climate control panel into a diagnostic mode. I have managed to do this but there is a lot more information churned out than is detailed in the original post. Does anybody have the full list of codes and expected results?

Also mentioned elsewhere on the net is a stored list of fault codes which apparently can be cleared. Anyone know how to read / decode these and clear them?

One last question, parameter 7 is supposed to give the refrigerant pressure in bar. With the engine off mine reads 3 and after starting the engine and running the compressor it gets up to 12. One poster commented that this should be around 14 - 16 bar. Would this shortfall be enough to cause the problems I have been experiencing?

I think I am going to have to take the car to the stealership and prepare myself for pain!

Apologies for the length of the post - so much for the 'quick update'.

Regards,

Martin.

 

[miro]

Hi again, a quick update. Found THIS whilst trawling the forum. It explains how to put the climate control panel into a diagnostic mode. I have managed to do this but there is a lot more information churned out than is detailed in the original post. Does anybody have the full list of codes and expected results?

One last question, parameter 7 is supposed to give the refrigerant pressure in bar. With the engine off mine reads 3 and after starting the engine and running the compressor it gets up to 12. One poster commented that this should be around 14 - 16 bar. Would this shortfall be enough to cause the problems I have been experiencing?

If you are going into the dealership they will read the codes for you.

When you go to regas the system you will need to consider that most AC people do not work for dealerships and so they will do the fastest job they can.

What is ideal is for the car gas to be vacated so that the number of grams can be measured (mine was 350 and it was meant to be 750). Then re-inject the gas according to the difference in the weight of the gas bottle (not pressure).

The other thing is that you want the EXTERNAL refill compressor to run for at least 30 minutes on the empty system because that will refresh the drier cartridge in the system.

If you ever service the AC and open the lines they say to replace the drier cartridge which is covered by bolt on top (the earlier model AC units). The problem is that the bolt thread corrodes and if you try to remove the cover it destroys the thread and then a whole new condenser (the big aluminium AC radiator) is needed to refresh that thread.

So in other words avoid replacing the drier cartridge. The alternative is to run the EXTERNAL refill compressor for 2 hours on an empty AC system (car is normally not running). This dries out the lines and drier cartridge.

 

[Rory]

I know some people will be horrifed but you could take into KwikFit - they apparently have magical new computer controlled (so the KF monkey can't do too much wrong) machines that will evacuate, lubricate & recharge your a/c for (I think) £45.
If it doesn't blow colder when they've finished then they don't charge.

 

[nickcc101]

Just bought a w 203 c 180 estate with faulty aircon (not working). Non Merc dealer sent for recharge but the system still u/s. Had to send to Merc dealer Exeter for computer to be reset. Fault was obvious as esr warning light on at all times.

 

[Barticus_UK]

Hi all, just another update (hopefully the last!)

Car went to the dealers yesterday to be checked on Star Diagnostics. Technician emerged 20 mins later and told me that there were no faults at all on the car and no faults stored. He did comment that the gas was low and suggested that this may be the culprit (as someone on here had said also). He said they could re-gas the car there and then and that it would cost, including the diagnostic charge, 'about' £150 but that I would need to monitor it over the next few weeks. If it died again they would have it back in to find / repair the leak at my cost (as the gas they fill it with has a dye added) and re-gas the system again free of charge. An hour and a half later I was presented with a bill for £140 and my car returned to me washed and vacuumed and with fully working air con. I just hope it stays that way.

Thanks to all for the replies.

Regards,

Martin.

 

[miro]

my car returned to me washed and vacuumed and ............. I just hope it stays that way.

Be aware that you may have to wash and vacuum the car !

 

[smiddyboy1]

is the noise away?

Barticus uk.... did the re-fill take the noise away????

I've only had my car for around 6 weeks, when i bought it I made a point of getting them to re-gas it just so that it would be ice cold, however ive starded to hear the whistling noise like you described and the drivers side isn't as cold as the passenger side.
Could the guys who recharged it maybe have not closed the system properly and some gas is escaping when i use the air-con, or could i be barking up the wrong tree???

I dont have the digital climate control to check the gas level / pressure, but i do have command and was wondering if it would throw up an error code on that by doing the "mute 1 & 3" thing.

thanks in advance.

 

[miro]

Barticus uk.... did the re-fill take the noise away????

I've only had my car for around 6 weeks, when i bought it I made a point of getting them to re-gas it just so that it would be ice cold, however ive starded to hear the whistling noise like you described and the drivers side isn't as cold as the passenger side.
Could the guys who recharged it maybe have not closed the system properly and some gas is escaping when i use the air-con, or could i be barking up the wrong tree???

I dont have the digital climate control to check the gas level / pressure, but i do have command and was wondering if it would throw up an error code on that by doing the "mute 1 & 3" thing.

thanks in advance.

Stupid people regas by pressure and not weight of gas. That is the problem. they only half filled the system.

 

[smiddyboy1]

to miro

Miro, i forgot to mention that it was working fine up until 5-6 days ago when i started hearing the hissing / whistling, do you still think it's been half filled or possibly a leak also?

 

[miro]

Miro, i forgot to mention that it was working fine up until 5-6 days ago when i started hearing the hissing / whistling, do you still think it's been half filled or possibly a leak also?

You better not run the system till you find out. Otherwise you will need a massive overhaul to get back to square one.

If the service had been done correctly then a leak would have shown on the pressure guage.

 

[smiddyboy1]

update

The car is booked in for Wednesday, so I'll keep you updated.
I was thinking about taking it to Kwik-Fit for a re-charge as mentioned on this thread but when i phoned them to ask about it the guy said "i dont know!!!! we only went on a course on how to use that machine, i just plug it in and go back to it in an hour".
Didn't really install much confidence of thier ability so the car is booked into an independent mercedes specialist, update in a few days.

 

[smiddyboy1]

update

Well turns out to be a leaking Condensor!!!

I appears that the garage I bought it from had filled it, but everytime I used it the gas had been escaping,
I'll never know if they knew it was leaking and only filled it to get it out the door but at least it'll be working the way it should.

another point - I dont rate their MOT guys very hightly as the track rod end is Fu*^ed, when it was on the wheel free ramp for a general once over the guy phoned me to have a look, and you can move the front wheel about half an inch in each direction (front to back), i never felt it whist driving although people have been saying to me that the power steering will take up the play and you dont notice it.

thanks to all who helped