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The AC in the car is not working anymore. It is blowing warm air. I hooked up a gauge to the low port, and it shows 80 psi regardless of whether car is running or not or if AC button is turned on. I believe, this indicates that the compressor is not running. There is no visible damage to condenser and piping, at least to the sections, which are easy to see. How do I test the compressor? Is there a way to test the clutch on it?
I had the same thing a month back. Went from blowing cold to a weak and intermittent cold air and over a week or so it just stopped blowing anything but ambient temperature air. One unusual thing was there was a variation in temperature between the two front air vents. Check and there was plenty of gas. It could be the solenoid on the compressor itself of just the compressor. I found the OEM Denso compressor on sale and after 115k miles, elected to just change it. It seems to be about this mark in miles where they fail noting they are always running. Replaced, regassed and everything returned to order.
Last edited by BlackML550; Jun 9, 2025 at 04:58 AM.
I took some screenshots with the AC parameters. Do you see anything wrong? I think, my problem is the control valve, like in the post referenced above. Sometimes, very rarely, AC starts and works just fine, but most of the time it just blows warm air. How do I buy the correct valve? The compressor is probably original Denso. Front plate of the compressor says "PPS-GF40". The valve has "7Y09Y" and "II" on the back. Also, I would greatly appreciate more details on how to remove it. Is it better to leave, say, 5-10 psi in the system (or more)? What tool can I use to pull it out? The only thing sticking out is a connector cap. How do I grab it?
Thanks.
Its a false economy trying to repair the compressor on a 17 yeat old car and still not be sure if it's the right fix. For probably not much more in cost, I'd be changing the whole thing. The OEM compressors are less than $400 and if you're going to have to remove it anyway, makes sense to the change the whole thing?
Its a false economy trying to repair the compressor on a 17 yeat old car and still not be sure if it's the right fix. For probably not much more in cost, I'd be changing the whole thing. The OEM compressors are less than $400 and if you're going to have to remove it anyway, makes sense to the change the whole thing?
That's the whole point: try to repair it without removing the compressor. This post #17 W211 E320 Bluetec AC Temp B/12/2 question. - MBWorld.org Forums says it can be done. Removing the compressor looks difficult. Yes, it is only 3 mount bolts and 2 lines, but there is no room to work. I've read that I would need a ton of specialized tools to unmount it. Also, I have no idea how to take it out. It looks like the car frame was built around the compressor. On the other hand, if I can pop out the valve without removing the compressor, it could be much simpler repair. Also, if I replace just the valve, I don't need to touch the belt.
E350, E320 Wagon, E320 CDI ML320CDI Sold, SLK350 Sold, 300D For Sale.
Removing the compressor is a pain til you find the secret. Drain coolant and Power Steering reservoir. Pull belt, Power steering reservoir and pump. Then loosen the driver side motor mount bolt about an inch. Raise the motor about an inch or 2. This gives clearance for the lower compressor bolt to the sway bar.
The compressor shaft is always spinning when motor is running. Start the car and look at the 7mm hex shaft on the front of the compressor. It should be turning. If it is not, then the break away has broken decoupling your shaft from the pulley.
I had mine swapped out in my driveway by an AC specialists. Didn't remove power steering or drain the coolant. Did it all from above. I didn't watch him so I can't tell you how he did it. He did the swap and regassing and testing all in less than 2 hours.
My earlier point about the false economy is driven by the fact that these compressors start to fail from about 120k miles onwards. Changing out one part now only for the compressor which might be near the end of its life might mean you're doubling up. They're always working so they wear probably faster than other setups. On a 2008 model I expect you'll be close to or past that mileage - but you didn't state how many miles.
Last edited by BlackML550; Jun 30, 2025 at 03:27 AM.
I One unusual thing was there was a variation in temperature between the two front air vents.
did this get resolved as well after you replaced your compressor? i'm getting this issue too and wondering if it's indicative of a failing compressor. seems unrelated but you never know with these vehicles!
E350, E320 Wagon, E320 CDI ML320CDI Sold, SLK350 Sold, 300D For Sale.
Originally Posted by BlackML550
I had mine swapped out in my driveway by an AC specialists. Didn't remove power steering or drain the coolant. Did it all from above. I didn't watch him so I can't tell you how he did it. He did the swap and regassing and testing all in less than 2 hours.
My earlier point about the false economy is driven by the fact that these compressors start to fail from about 120k miles onwards. Changing out one part now only for the compressor which might be near the end of its life might mean you're doubling up. They're always working so they wear probably faster than other setups. On a 2008 model I expect you'll be close to or past that mileage - but you didn't state how many miles.
For a W211 with a M112 or M113 V6 or V8, I don't think it is possible to do it without pulling the power steering pump. I suppose it could be done without draining the coolant, but 10 minutes to drain and 10 to refill gets the coolant hose out of the way and avoids return line breakage possibility. The bottom forward bolt will not come out without raising the motor about 2 inches. And the aft is so much easier to get with the PS pump removed. I used to have a E320 CDI with straight six diesel, and everything was much easier to get to than the v6 or v8.
I had mine swapped out in my driveway by an AC specialists. Didn't remove power steering or drain the coolant. Did it all from above. I didn't watch him so I can't tell you how he did it. He did the swap and regassing and testing all in less than 2 hours.
My earlier point about the false economy is driven by the fact that these compressors start to fail from about 120k miles onwards. Changing out one part now only for the compressor which might be near the end of its life might mean you're doubling up. They're always working so they wear probably faster than other setups. On a 2008 model I expect you'll be close to or past that mileage - but you didn't state how many miles.
Thanks for the reply. 108,414 miles now. I am uncomfortable lifting the side of the engine, even 1 inch. What kind of stresses it creates? Can it damage transmission or gaskets? Looks like the right way to do it is through the top/front by removing the fan and other stuff. The center of the compressor spins fine. No abnormal noises.
E350, E320 Wagon, E320 CDI ML320CDI Sold, SLK350 Sold, 300D For Sale.
If you have a W112 E320, there are only 2 ways to get the bottom forward bolt out. Raise the engine or remove the sway bar. If you loosen the top bolt of the left engine mount, you are effectively doing the same thing you would do for changing a motor mount; engine has to be raised to remove the old, and install the new. If you are uncomfortable doing this, then absolutely take it to an AC shop or even better an indy MB shop.
I have W211 E350, not W112 E320. Did you mean W211 E320? I don't know how similar the layout is. Will starting this car without refrigerant lock the AC system so it would only unlock with a STAR? Is it possible to recover the refrigerant, use the car for a while, and then refill and restart AC without specialized tools? I've read that disconnecting refrigerant pressure sensor will trigger low refrigerant condition, which can only be reset with STAR. Thanks.
E350, E320 Wagon, E320 CDI ML320CDI Sold, SLK350 Sold, 300D For Sale.
Yes, I indeed meant W211.
First things first. You first need to see if your compressor is seized or the clutch lock has decoupled from the compressor. Get a visual of the compressor face and note you have a pulley, a disc, and a 7mm hex in the center. Behind the disc is a pulley lock, that physically breaks if the compressor seizes.
Testing is simple; start the car and see if the 7mm hex spins with the pulley. If it does, then your compressor is not seized. If it remains stationary then compressor is seized and must be replaced. Mine failed at about 125k Miles. The car does not use an electromagnetic style compressor clutch.
If it is still spinning, then perhaps you can get by temporarily with refrigerant servicing. This will likely be short lived, as if you have a leak, it will continue to leak.
If you disconnect the connector that goes to the pressure temperature sensor, then N10/1 will sense this and not allow your compressor modulating valve to flow freon. Simply disconnecting and reconnecting will not require a star reset. In fact, for a compressor change, star is not needed at all. You can use it to see the condition of B10 temp pressure sensor, and you can use it to send a signal to the compressor, but that is really about it. Hope this helps.
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