w203 aircon compressor clutch problem

[JARushby]

Hi

I have a problem with my C220 CDI (W203). Aircon simply not working. Had it re-gassed and leak tested. No problem there. EC light goes out so no problem there. However, compressor simply does not engage. I managed to physically lock the compressor to the flywheel so the compressor was definitely turning (just a temp measure to ensure compressor was ok). cold air streamed out. So, it would appear there is an electricl problem or a problem with the clutch mechanism (the pully wheel has a black cover on the front of it which I believe is engaged by the clutch mechanism and spins the compressor.

I have tried to wire a positive lead from battery to the clutch but appear to be getting strange results. Before I wired the temp feed I measured the voltage and it seemed to show ~10v irrespective of whether the EC buttom was pressed or not. I was expecting 0v or 12v. When I wired the temp feed from the battery I could hear a light "click" when I connected the feed to the battery but still the clutch did not engage.

My diagnosis would normally be the the clutch mechanism was in some way faulty but to be honest I am not sure that I was connecting into the correct wire. I assumed that the positive feed to the clutch was the single lead that has a connector that sits on top of the air con compressor. Is this correct. the lead simply seems to connect there but there does not seem to be any obvious connection to the clutch. can someone please advise where the feed to be mag clutch actually is.

Also, when the clutch engages should the compressor drive shaft pull in so the black cover is pulled onto the pully "rubber" drive?

Sorry for so many questions

 

[television]

Any 1 sensor can stop it from working,,why not find an indie with STAR, it will pin point the problem

 

[JARushby]

Any 1 sensor can stop it from working,,why not find an indie with STAR, it will pin point the problem

Yep, I agree, but first I wish to exclude the possibility of the clutch mechanism being faulty

 

[television]

You can see the wires that go to the clutch,,it is no good just running a wire to it from the battery without disconnecting the wires on that plug. The single wire that goes the the front near the clutch is the one

 

[JARushby]

You can see the wires that go to the clutch,,it is no good just running a wire to it from the battery without disconnecting the wires on that plug. The single wire that goes the the front near the clutch is the one

Thanks for this. Just to clarify, The clutch has two wires that go to it (-ve and +ve). The positive wire has a connector that sits neatly on the compressor housing. I simply need to disconnect this connector and use a fused feed from the battery to the red wire that is connected to the clutch.

I assume I should hear a "clunk" when the clutch engages or if I do this when the engine is running the compressor "cover" should start to spin. yes?

Can you (from the front) see the compressor visibly engage if it is working ok?

 

[television]

Yes you can sometimes see movement, and you can do this with the engine turned off, and the click can be heard just by joining up 12 volts to it.

It can be difficult in measuring voltages without know if the plus or minus is switched. You can have a case where the object is always live and a single pole sensor switch just grounds it, to bring it into operation, this is why it is unwise to play with any thing else still plugged in to the object under test

 

[JARushby]

Yes you can sometimes see movement, and you can do this with the engine turned off, and the click can be heard just by joining up 12 volts to it.

It can be difficult in measuring voltages without know if the plus or minus is switched. You can have a case where the object is always live and a single pole sensor switch just grounds it, to bring it into operation, this is why it is unwise to play with any thing else still plugged in to the object under test

Thanks again for your help. What is the engaging mechanism. Is it a magnetic drive or it simply a case of the black cover(ie the drive to the compressor) making physical contact with the pully wheel. I have looked underneath the cover and there appears to be "rubber" drive on the pulley. Is this correct?

I strongly believe I have an issue with the clutch. Although not a final solution, could I simply lock the "rubbers" to the cover leaving the aircon permanentky on. Would this in any way damage the compressor further?

Thanks again

 

[television]

Thanks again for your help. What is the engaging mechanism. Is it a magnetic drive or it simply a case of the black cover(ie the drive to the compressor) making physical contact with the pully wheel. I have looked underneath the cover and there appears to be "rubber" drive on the pulley. Is this correct?

I strongly believe I have an issue with the clutch. Although not a final solution, could I simply lock the "rubbers" to the cover leaving the aircon permanentky on. Would this in any way damage the compressor further?

Thanks again

The clutch is only a magnetic device that locks it, I have never serviced one, as they are specialist things.

If the clutch has gone, there is not that much to lose, though I cannot confirm that this type of compressor was ever made to be run continuous as the operation is different in the way that they are controlled

 

[colifecape]

I have also found my air con`s died after winter. It was ok at the end of last year but it has been switched off since. From what you say about the compressor clutch, it sound the same principle as 3ph motor brake. A coil and a plate/ferodo which is held under tension till the coil energises.
So, are these units strippable for cleaning and checking gaps? I wonder about this as the dealer listed re-gassing mine last summer before I bought it.
( Theres also an odd higher pitch sound from the dash since iput the ac back on???)

Any suggestions would be magic, cause I always liked auto temp control.

C

 

[Alex Crow]

hi, what age and model please? you may well have the constantly running pump, the clutch system was phased out many years ago. just have a look at the front of the compressor, if it has a clutch it will be obvious to you as you clearly understand the basic principles of it. on the constant pumps the pumping effect is controlled by a bypass valve at the rear of the pump, this allows the pump to "short circuit" when not required, it can also be modulated giving varying levels of pumping. the other main advantage of this system is to reduce loads on the pump/clutch/ancillary drive system as the drive is engaged.

 

[colifecape]

Cheers, its a 2005 c180K SE.
OK, so a clutchless pump works off a loading valve, servo operated? Makes sense.
If I can get some peace from working weekends I might even get a chance to go rummaging.

Thx,

coli.

 

[Alex Crow]

what symptoms do you have? it seems you have no refrigeration from your post. is the acoff button illuminated constantly? have you had the refrigerant pressure tested?

 

[colifecape]

Basically, It does not blow cold. ACoff light isn`t illuminated. It also doesn`t always control the fan speed awfully well when altering temp. Worth resetting the heater controls/ flaps?

Anyways I think I`ll start with getting the refrigerant charged and checked since I`m feeling the large dealership in Motherwell I bought the car from may have been thrifty with what they claim to have done pre-delivery

THx
Coli.