[wyman]

2001 ml 320, ~72k MILES

Previously fuse 44 was blow last year.

Even turned to the max, no cold air. When I looked at the compressor, it makes a half turn then stops.

If freon is low does it prevent the compressor from working or I might have to replace the compressor?

 

[andreialta]

maybe freon is low. recharging it might be a solution

 

[43sqd]

There is nothing wrong with your compressor. The system needs a charge, probably have a small leak somewhere.

 

[Kajtek1]

For about $12 you can buy a bottle of freon with gauge attached.

 

[wyman]

i will give it a try tomorrow. it has been 100+ degree here today Napa... Even rolling down the window is still too hot.

 

[sergiu]

Even if the freon is low the compressor should work, it won't be as cold though.

The way you describe it, there could be something wrong with the clutch which drives the pulley, as part of the compressor assembly. If the clutch, for some reason, is no longer engaging or dis-engaging the pulley, you will have to replace the compressor altogether.

It's going to be expensive anyway so I would stick with an OEM part.

 

[supradupe]

if refrigerant is low, the compressor won't kick in. by the way, it's R134a, not freon.

 

[drewbush]

Have you checked to see if fuse #44 is blown again? Did they perform the aux fan wiring modification? As stated by others, check to see if the ac clutch is engaging on the compressor. Have the car running with the ac on, then look at the compressor. You should see the clutch on the very front of the pulley turning, if you dont watch it for a few seconds and see if it cycles on. If it doesnt, then you have a problem or two. It could be low on R134a, faulty sensor, bad compressor.

If you want the pdf file on the aux fan wiring mod, pm with an email address and I will send you the document.

 

[bavenda]

I have never recharged my A/C on my 99. Do I have bleed the system first? Do you have any recommendations of kits and where is the point where you connect the R134 into the system on an ML?

 

[Kajtek1]

Our 10 years old ML320 still work on original AC without a problem, so I never had to touch it. I am having leak on our E300td and the low pressure port is on the tubing below master cylinder. Since those cars share drive-train, I would assume ML is having the port in the same location.If you connect the gauge and it shows some pressure, that means you had small freon loss. No need to bleed or vacuum the system for just freon adding.
When the pressure shows 0 you can shoot a can of sealer/leak indicator and pray.

 

[wyman]

Tried recharging it still the same. I already checked fuse #44 and looks ok. The compressor cycles on, then stops, then starts again then stops and keep repeating the same pattern.

Have you checked to see if fuse #44 is blown again? Did they perform the aux fan wiring modification? As stated by others, check to see if the ac clutch is engaging on the compressor. Have the car running with the ac on, then look at the compressor. You should see the clutch on the very front of the pulley turning, if you dont watch it for a few seconds and see if it cycles on. If it doesnt, then you have a problem or two. It could be low on R134a, faulty sensor, bad compressor.

If you want the pdf file on the aux fan wiring mod, pm with an email address and I will send you the document.

 

[fabbrisd1]

Sounds to me like a not-small leak..any aircon shop can do a vacuum test to tell you for sure.

If it turns out to be the compressor, then these guys have been good to me on air con parts:

Air Conditioning Compressor from 1AirConditioning.com

 

[cmitch]

If the compressor is under duress, it could do this, eventually burning up the clutch. I suspect this is what happened to mine, but no way to know. The pistons in the compressor (7 of them) run off an eccentric plate that works off centrifugal force. The faster the compressor turns, the more the stroke on the piston. There is a 'caliper' that is attached to the bottom of the piston that has a half-ball pin in the top and bottom. The 'flat' of the balls ride the flat eccentric plate on both sides, operating the pistons. One of these split 'balls' came loose, destroying my compressor, internally. The brass plate was so worn, it allowed enough room to lose the pin.

You can turn the compressor, by hand, since the clutch isn't engaged, leaving it free. When my new one was installed, it turned easily. It would be much easier to turn if there was no pressure in the system, so, maybe you should take it to an indie and have the system evacuated. The plate on front of the clutch is what you turn, since it is keyed to the shaft. If you feel hard spots in the compressor, then I'm sure this is why it engages, makes a quick turn, then disengages. There is possibly, more load than your clutch is designed to pull, causing it to do this. All of this is, somewhat, speculative but is all I have to offer you, at this time.

I hope it turns out okay BUT, be prepared to install a new compressor, expansion valve and dryer/accumulator. fabbrisd1 just gave you an excellent source for the compressor. BE SURE, if you have to order, to specify the 'KIT'. It is $65.00 cheaper to buy the KIT instead of the 3 components separately. Also, the aftermarket they sell is actually supposed to be better than the OEM. They told me the OEM had a design flaw that has been addressed in the aftermarket model and they said they sell twice as many aftermarket models but have about 1/4 the call backs of the OEM's

 

[sergiu]

cmitch,
why the expansion valve and dryer/accumulator also?

 

[cmitch]

cmitch,
why the expansion valve and dryer/accumulator also?

When a compressor fails, metal filings and other failure related trash clog up the dryer accumulator and expansion valve. When the new compressor is installed without replacing these two components, that trash and metal filings ultimately get slung back into the system, resulting in the very pre-mature failure of your new compressor.

I disassembled my old compressor and it was a mess on the inside. Here are some pics:

Pic 1 is a view of one of the pistons. As I mentioned earlier, there are rounded pins that are flat on one side that set inside the piston.

Pic 2 is a view of the eccentric plate I referred to and I assembled a piston with the pins and stuck it on the plate so everyone can see how the pistons ride on it. Notice the spline on the shaft for the clutch.

Pic 3 and 4 is a view of the pistons stuck in the cylinders. Note, in the top view picture the damage done when one of the pins rattled around inside the compressor.

 

[sergiu]

cmitch,
your're very thorough and I really appreciate sharing this. I can see in last picture how dirt just scraped the sides of those pistons, not just one but all of them
I changed my compressor last october due to clutch failure, I think, because the face plate of the clutch was just gone. So I assumed it was the clutch. I only changed the compressor, with a DANCO (?) one made in Japan, I believe it was... but didn't think to change the other two components, however, did not turn the AC on since, other than for testing that it works. I was wondering if it's too late.... The guy purged the freon into a special machine and pumped it back in after replacing the compressor, maybe that washed some of the shavings away but can never be too sure.

 

[43sqd]

Tried recharging it still the same. I already checked fuse #44 and looks ok. The compressor cycles on, then stops, then starts again then stops and keep repeating the same pattern.

When a compressor repeatedly cycles on and off, it is an extremely good indication that the system is low on refrigerant.

You said that you have tried to recharge it, but I can only assume that you used the one can system with a small hose. The only proper way to do this, especially if you have no working knowledge of air conditioning, is to have it professionally done. The system must be evacuated, tested for leaks and then the proper amount of refrigerant installed to see if the entire system is working properly.

 

[cmitch]

cmitch,
your're very thorough and I really appreciate sharing this. I can see in last picture how dirt just scraped the sides of those pistons, not just one but all of them
I changed my compressor last october due to clutch failure, I think, because the face plate of the clutch was just gone. So I assumed it was the clutch. I only changed the compressor, with a DANCO (?) one made in Japan, I believe it was... but didn't think to change the other two components, however, did not turn the AC on since, other than for testing that it works. I was wondering if it's too late.... The guy purged the freon into a special machine and pumped it back in after replacing the compressor, maybe that washed some of the shavings away but can never be too sure.

If you only had a failed clutch, then you're probably okay. BUT, are you sure? Do you still have the old one to disassemble to see if there's any internal damage?

 

[cmitch]

When a compressor repeatedly cycles on and off, it is an extremely good indication that the system is low on refrigerant.

You said that you have tried to recharge it, but I can only assume that you used the one can system with a small hose. The only proper way to do this, especially if you have no working knowledge of air conditioning, is to have it professionally done. The system must be evacuated, tested for leaks and then the proper amount of refrigerant installed to see if the entire system is working properly.

He could have a bad expansion valve, creating the cycling on off on a fully charged system. But, like you said, he'll never know if he doesn't properly charge it, first. I doubt the compressor is bad, either. At least for his sake, I hope it isn't.

 

[43sqd]

He could have a bad expansion valve, creating the cycling on off on a fully charged system. But, like you said, he'll never know if he doesn't properly charge it, first. I doubt the compressor is bad, either. At least for his sake, I hope it isn't.

Yes, all very true.