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Discussion Starter #1
Air con problem on my W210.
It was working fine a week ago - now everything appears normal but it doesn't cool the air. Compressor never starts. No fault codes.

Checked out many (Most?) of the posts on this forum -really useful, thanks.
but one further question,
I read out all the sensor settings and #7 is 00, so zero refrigerant pressure,
Is the zero pressure the cause or the effect?
I read somewhere on the forum that the compressor wont start with zero pressure - is that correct, or is it that the non running comressor is the cause of the zero pressure?

If its the cause I guess I have a leak and then need regassing,
If its the effect what else would cause the compressor not to start?
 

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Current 2017 GLE350, 2007 S550, 2002 S430, 1998 ML320 Deceased 74 240D, 92 400E, 97 E420, 13 GLK350
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Bill - what year and model is your car?

Some basics:

Assuming you have a Denso with a clutch, if the center clutch on the compressor isn't turning then you either have:
1) an electrical problem so a signal is not reaching the compressor clutch
2) A fried compressor that is locked up and has potentially fried the clutch (with the engine off, should be able to freely turn the center hub by hand.)
3) or a low R134a charge problem (which blocks the signal to the compressor clutch so that the system does not pull a vacuum and bring in atmosphere and ruin the compressor)

Sounds like door number 3) for you. However, if the R134a has been repeatedly leaking out, and repeatedly filled by the previous owner, then some of the compressor oil has leaked out (evidenced black oily streaks around high pressure line connections). Not replacing the oil will lead to premature compressor failure.

Couple of choices: - 1) take it to an independent Air Con shop and have an evac and refill for about $80. It will fail the vacuum test and they may not refill for you. It will also leak out again. However, the advantage is they will remove all moisture, and replace the exact amout of PAG oil and R134a that you need. They will also give you an idea of where the leak is.
2) Go to an auto parts shop and buy refil R134a. One of the cans should contain oil to makeup what was lost from the leak. You may want to consider getting a second 12oz can with a 'stop leak' product. I have had success in putting in one stop leak can on an older E420 to seal the O-rings. The number of 12oz cans you get will be predicated on the charge specified on a label in your engine bay. Should also add a bit of leak detector dye to find the actual location of the leak. 12 oz Cans are about $15 each.
3) Tear down the system and replace all of the O-rings if the leak detector dye shows the location. (A little black oil residue is another indicator) This is the proper fix - assuming the leak is at the O-ring and not the condenser. Evacuate the system, and refill with correct amount of R134a and oil. This is a bit challenging to do in your garage, but more time consuming that anything else.

Good luck
 

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Discussion Starter #3
Thanks atmsmshr,
Car is E240, V6 2.6 ltr petrol here in UK.
Year is 2000, - owned this since new, its still a great car (except for the rust grrrrrrr).
I also read on here somewhere that you can force the A/C clutch to pick by pressing both AUTO buttons for 10 secs. Tried it and its true, clutch picked and compressor runs - but still no cooling.
So your option 3) was correct I guess, and it needs recharging. A/C worked fine a week ago so the leak has happened suddenly so probably needs a good checkout to find the leak, I know a good independent MB garage so just need to decide if its worth repairing, usually its more important to have a heater inthe UK!
 

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W210.265/2001, W220/S500/2000, Porsche 997 C2S/2006, GMC K1500/1992
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Bill if your AC has been working good and suddenly the compressor did not come on there is 2 possibilities.
1. Leak has caused all the freon leaked out from the system.
2. Your pressure sensor is defectives, read the freon at 0 bar.
Cheapest way to take care of the problem:
Spend $18, buy a can of R134a with a pressure gauge. hook to your low side suction valve, if you have no freon, the pressure of the can will fill the system. After the 1st can, you should able to turn on your compressor. If you can not fill the 1st can, then you have a bad pressure sensor at the top of the drier. You have to replace it or find a indie to do the job.
 

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W210.265/2001, W220/S500/2000, Porsche 997 C2S/2006, GMC K1500/1992
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As you said, if you refill and the AC compressor works, but no cooling, there is a leak, it is easy to add dye into the system as you add the freon, use violet light to detect the leak, most of it will be at the high pressure valve or condenser or seals around the driers and hose connections. It is very inexpensive to replace all the seals and drier. The labor is expensive, so DIY will help.
 
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