Measuring AC Compressor Clutch Gap - PeachParts Mercedes-Benz Forum

deanyel · #1 05-21-2006, 12:49 PM

I've done a search but dont' get it - how do you measure the compressor clutch gap? Can it be done on the car or does the compressor have to come off? Or does the serp belt have to come off? I just don't see a place to measure. Car is a 400E, MB compressor part # 000 230 06 11 80, which I believe is a factory rebuilt Nippondenso. I'm getting a compressor clutch blocked fault code and this seems to be a good suspect. Any help appreciated.

#2 05-21-2006, 02:03 PM

Quote:

Originally Posted by deanyel

I've done a search but dont' get it - how do you measure the compressor clutch gap? Can it be done on the car or does the compressor have to come off? Or does the serp belt have to come off? I just don't see a place to measure. Car is a 400E, MB compressor part # 000 230 06 11 80, which I believe is a factory rebuilt Nippondenso. I'm getting a compressor clutch blocked fault code and this seems to be a good suspect. Any help appreciated.

it can be measured on the car you use a feeler gauge between the idle pulley and the front clutch housing, i am not sure what the value is, but before i would measure gap i would check the wiring harness plug on the compressor, i have seen this same code caused by the wires at the plug coming loose, open the plastic housing and see if this is the case, it seems to happen sometimes when the motor mount on the drivers side breaks, and when you accelerate the engine raises up on that side and over time damages the wire.

deanyel · #3 05-22-2006, 09:23 AM

Thanks, the pictures helps a lot - I'll take another look at it later this week. I did have a wiring problem which I believe I fixed last week. The speed sensor wire was broken so I spliced it up and got the compressor to come on a few times, but then it started to cut out again. But I'll go back and look at the wiring too.

jcyuhn · #4 05-22-2006, 11:09 AM

It's easy to measure on the car using plain old feeler guages. I'm not familiar with the underhood layout of the 124.034, you may have to go in from the bottom of access from up top is too tight. Attached thumbnail has it correct, you measure just in front of the pulley turned by the serpentine belt.

Gap is specified as 0.50mm plus or minus 0.25mm. My unscientific observation is that clutch engagement gets a bit flaky when the gap gets up near 0.90mm. Sometimes you can get it working by degreasing the clutch using brake parts cleaner or similar. No disassembly required, just spray it in there.

I checked the gap on my 124.028 while servicing the a/c a few months ago. It's up around 0.80mm and works fine; compressor never drops out on that car. (Knock on wood...).

- JimY

jbaj007 · #5 05-22-2006, 11:30 AM

Shade tree quicky check.......snug fit of a credit card.

GVB · #6 05-22-2006, 11:44 AM

It sounds like you have a bad compressor. Those codes usually come on and stop the compressor from engaging when it is starting to go bar. Like when the compressor is not turning at the same rpm with the engine. You can check the rpm from the compressor to the engine, but you are going to need some equipment

GVB · #7 05-22-2006, 11:45 AM

By the way, don't worry about gap. Wasting time.

deanyel · #8 05-22-2006, 11:53 AM

And went out and took a picture of it - I may have another problem. My compressor does not look like the one in Carson356's picture. The one in the picture is stamped "17" on the side which presumably is for a Nippondenso 10PA17. My compressor is stamped "20" in the same place which presumably means Nippondenso 10PA20. I found some other information to indicate that a 17 is an "axial" design while a 20 is a reciprocating piston design. Not sure what the difference would be on a clutch (if mine has a clutch) but I sure don't see a place to measure a gap. Picture of my compressor is attached. So I'm going to go back to working on wiring - seems easier. Thanks for the help.

#9 05-25-2006, 11:51 PM

mine was mainy generic in nature, but i marked your picture where you measure.

deanyel · #10 05-29-2006, 07:54 PM

I finally got back to this and it does appear, if I'm doing it right, that the clutch gap is too large - around .9 mm when it's supposed to be .5 mm +- .15 mm. I now know my high/low pressure sensor is fine, my rpm sensors all hooked up, etc. So it looks like it's something at the compressor and/or clutch. I give the compressor 12 volts and nothing happens, nothing moves, nothing clicks, just silence. It's hard to believe the compressor is bad - when it would kick on it worked like a champ. But now is just won't kick on at all. There's an old Larry Bible post that narrows this down to "clutch coil is open" or "air gap is too wide". I'm guess I'm going to get the pin wrench and try to take off and adjust the spring plate. Any words of wisdom appreciated.

deanyel · #11 06-01-2006, 10:39 AM

Back to this again - I was measuring the wrong place. It is exactly where Carson spotted it on the latest picture but I say with some confidence that it isn't even possible to measure the clutch on this particular setup. The gap is actually inside the outer diameter of the pulley. You would need a crooked, perfectly custom designed gap tool to have chance of an accurate measurement. Turns out it is a Nippo 17 but seems to have some sort of an unusual clutch.

The good news is that adjusting the gap is quite easy but that does not seem to be the problem as I played around with the gap and couldn't get it to work. The other strange thing about this clutch is that it has no pin holes for a pin wrench. But I found that an oil filter wrench/tongs worked just fine for locking the wheel as there's only 12 lbs of torque on the center bolt.

I also found that shims are not easy to come by. Two dealers had no idea what I was talking about. Several retail stores also clueless. Finally found some shims at an AC rebuild shop. I went looking for them thinking that adding shims was required to reduce the gap - as I read in a post here somewhere - but indeed the truth is the more intuitive approach - removing shims reduces the gap. It is good to have shims of various sizes for flexibility however.

So still no clutch engagement - seemingly down to two possibilities: 1) clutch coil problem, and 2) leaking front seal, which according another post here can cause the clutch to somehow slip on the shaft. I did see some evidence of a green liquid, presumably freon, when the clutch was out.

#12 08-01-2006, 08:09 AM

Here's a new twist on the 124 compressor kicking out upon slip detection:

I was told by a long time MB tech that these compressors sometimes kick out when they get older not due to clutch slip, but because as the compressor wears, internal thrust allows the shaft or wheel that is looked at by the rear rotation sensor to move away from the sensor which aggravates the problem.

The only known solution is to replace the compressor. It MIGHT be possible to modify the sensor so that it seats further into its hole.

Mine has been kicking out occasionally after restarting soon after shutting down. I have theorized that the load is heavy under these circumstances because the high side pressure has not had time to bleed off.

Friday evening, in 100 degree heat, after running on the freeway for about 15 or 20 minutes, the a/c stopped cooling and I thought that something catastrophic had occurred. After stopping the car and restarting the engine, it was okay again. I am now wondering if the worn compressor/sensor issue is my problem.

Have a great day,