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  #1  
Old 04-30-2011, 12:17 PM
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A/C compressor interchangeability

Hello all,

I'm new to the forum, so please forgive me if what I'm about to ask has already been discussed...I did a search, however, and came up with nothing definitive.

I want to replace the A/C compressor on my '87 300D with a low cost used unit. It's a Denso 10P15C. I was in my local U-pull it junk yard yesterday and found 7 potential donor cars, but all had 10PA15C or 10PA17C compressors. The manifolds looked different on some of them, but I saw at least one of each with manifolds that looked the same as my 10P15C. I realize they have a different part number for a reason, but does anyone know, or better yet has anyone tried, to interchange any of these compressors? If it won't work, why not...what are the problems from a practical (fitment and use) point of view? Finally, am I correct in assuming the 10PA17C is a higher capacity unit?

Thank you in advance!

Willis

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  #2  
Old 04-30-2011, 07:03 PM
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What's wrong with your compressor? Are you sure it isn't a Klima relay, hose or clutch problem?

The 300D and 300E of the same year have the same cabin volume but the D has the 10PA15C and E has the 10PA17C. I doubt it's a capacity difference. IIRC, the 190D, 300D and 300SDL of that vintage use the 15. That's a wide variance in cabin volume for a single compressor to cover for capacity to be a factor between gas and Diesel 124s.

It's easy to swap manifolds so that shouldn't stop you from getting a compressor from a different year or model MB. If you can swap the clutch and live without a compressor rpm sensor, you can expand your search for a 10PA15C to Hondas, Toyotas, etc.

Sixto
87 300D
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  #3  
Old 05-01-2011, 02:23 AM
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Thanks for the reply Sixto, I appreciate it.

The car is blowing the #7 fuse immediately upon engaging the A/C. I've done a pretty good amount of testing, and I think the compressor clutch is shorted out. The Klima relay is good, the push button unit is good, the blower fan and regulator are good. If I unplug the wires from the top of the compressor, the fuse doesn't blow (of course, the compressor doesn't engage either). The system is fully charged and was cooling fine before blowing the fuse one day in traffic...and each time I've replaced the fuse and tried again since.

I have another 10P15C which is no good but has a good clutch. I would prefer to swap clutches without taking the current compressor out of the car. I've read some posts by people who say they've done it. I can't figure out how they got the retaining nut off the clutch. Some said they used vice grips or a strap wrench to counterhold, but I don't see how. The clutch has no more than a millimeter and a half of exterior circumference width to grip onto, and it isn't even flush with the circumference of the pulley - no strap wrench I tried would counterhold on that. And I don't see anything to put vice grips on to counterhold. So I'm giving up on that strategy unless you or anyone else has some words of encouragement (and enlightenment)?

Also, do you know what the difference is between the 10P15C and the 10PA15C? Mine is a 10P15C...but like you said, the 10PA15C seems to be much easier to come by.

Thanks!

Willis
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  #4  
Old 05-01-2011, 07:12 AM
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My diesels have the infamous Delco R4 units so I can't speak specifically to your compressor. However my '98 Nissan has an axial Zexsel AC compressor with a clutch-coil winding that opens after it gets hot. A new clutch is NA, so I got a used compressor just so I could swap the clutch coils. Don't want to disturb or lose the freon, as except for the intermittent coil, the AC works perfectly.
I would swap the clutch on yours if at all possible. Are there any holes, slots, or openings in the face of your clutch-plate that you could fabricate some sort of holder to fit? Otherwise, you may need to try an impact-gun.
Once you get it loose, be sure not to lose any shims or washers you find on the compressor-shaft.

Happy Motoring, Mark
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Old 05-01-2011, 12:27 PM
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The clutch engages through battery. If it's like my sdl, it's 12v. Unhook the connector, and figure out what is which pole on the connector. Hook it directly to your battery. Then use your strap wrench to hold while you undo the center bolt. I dont' know that i'd recommend leaving the belt on as a counterhold...

You might undo the compressor from the engine and turn it so the pulley faces upwards, and use and impact wrench and extensions to take the nut off. Some of them can be a lot of fun and giggles to get off if someone used copious amounts of loctite on that part...
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  #6  
Old 05-01-2011, 01:16 PM
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To diagnose a shorted clutch coil in my car, I hooked up an ammeter between the Klima and clutch. I saw ~20 amps which is 5 times the spec of about 4 amps. I sacrificed fuses in increasing capacity to confirm. I suppose measuring the resistance would have been easier but I didn't have a spec. You can deduce the resistance spec if you know the current limit is 4 amps.

I replaced the clutch in an 87 300D removing only the radiator. An SDL has more room so it can be done. The snout nut (or bolt in some cases) is easy to remove because it's not on very tight. Forget a strap wrench because the pulley is free to turn relative to the driven plate. There isn't enough driven plate surface for a strap wrench to grip. Borrow or rent an AC clutch holding tool from an auto parts store. The circlip holding the pulley is difficult to reach but it's the circlip holding the coil that will push your sanity across the line. I got a Harbor Freight circlip pliers kit and filed down the pincers for both enough jaw and reach. The circlips have flat and rounded faces so note how they should be installed. Keep track of the shims setting the clutch gap. You might have to play with a collection of shims to get the gap within spec. I got lucky keeping the shims with the pulley and driven plate as a set.

I think there's more room to work if you tilt the compressor down rather than up. That's what did at the yards looking for usable coils. I didn't want to see how far I could bend the 20+ year old AC hoses and fittings in my car.

This is the AC clutch wrench commonly available to borrow or rent at auto parts stores. You have to fiddle with how you use it because all the ND compressors I see on MBs have 4 notches rather than 3 -



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87 300D
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  #7  
Old 05-01-2011, 01:18 PM
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I forget the difference between P and PA. It might be the difference between a nut or bolt in the snout. It might also be the difference between 4 o-rings and a formed gasket between the compressor housing and the manifold. It doesn't help that some parts places list the same replacement clutch components and some lists dedicated components.

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Old 05-01-2011, 01:54 PM
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That's why I told him to use 12v directly from the battery to engage the clutch. Then he can use the strap wrench...
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Old 05-01-2011, 02:03 PM
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Quote:
Originally Posted by amosfella View Post
That's why I told him to use 12v directly from the battery to engage the clutch. Then he can use the strap wrench...
Of course, if there's a serious short, all that will accomplish is to fry something!

Happy Motoring, Mark
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Old 05-01-2011, 02:37 PM
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If you're taking the clutch off because it's fried anyways.....
I didn't say the battery had to be connected to the car... lol When I did mine, I used a spare battery from a large cat gen set that I had laying around..
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'04 E500 wagon 4matic
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  #11  
Old 05-01-2011, 03:40 PM
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Thanks guys. Sixto, I used your method to double-check my diagnosis of bad coil...much appreciated, thanks. I got 18.5 amps draw...so I think that probably does it. Does anyone think I can just replace the 16a #7 fuse with a 20a fuse and call it a day? I'm guessing no, but I figured it's worth asking.
I also took the advice to try an impact wrench. I tried it on the 10P15C on my workbench, which is the would-be clutch donor (the clutch on this one draws 3.5 amps, BTW). The nut flew right off to my amazement. There was a lock washer behing the nut, but I don't see a retaining clip...am I looking in the right place? Of course, the clutch plate didn't slide right off.

Thanks!

Willis
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  #12  
Old 05-01-2011, 04:42 PM
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Quote:
Originally Posted by Willis View Post
Thanks guys. Sixto, I used your method to double-check my diagnosis of bad coil...much appreciated, thanks. I got 18.5 amps draw...so I think that probably does it. Does anyone think I can just replace the 16a #7 fuse with a 20a fuse and call it a day? I'm guessing no, but I figured it's worth asking.
I also took the advice to try an impact wrench. I tried it on the 10P15C on my workbench, which is the would-be clutch donor (the clutch on this one draws 3.5 amps, BTW). The nut flew right off to my amazement. There was a lock washer behing the nut, but I don't see a retaining clip...am I looking in the right place? Of course, the clutch plate didn't slide right off.

Thanks!

Willis
Once you get the clutch & pulley off, there's probably a spring-clip securing the coil to the compressor nose.
Sometimes, there are shims or washers on the compressor-shaft, BEHIND the clutch-plate. Be sure to reinstall any you find on your original compressor after you get the new coil installed.

Happy Motoring, Mark
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  #13  
Old 05-01-2011, 04:44 PM
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In my case, the coil alignment slot wore the compressor housing pin allowing the coil to contact the pulley. The contact wore the coil winding insulation. It was 20 amps then but sure to keep rising as more insulation wore off. 20 amps is also a heck of a lot of continuous draw on the 65 amp alternator.

Most auto parts stores lend or rent a puller to extract the clutch plate. You can gently pry the clutch plate off the compressor but you risk deforming the pressure plate and thus messing the air gap beyond adjustability. You don't want to score the clutch contacting surfaces either.

Here's some guidance on pulling the clutch -

http://www.pelicanparts.com/techarticles/911_Nippondenso_rebuild/911_Nippondenso_rebuild.htm

This article has better pictures and really not too different for a Nippondenso compressor. I didn't need a puller -

http://www.bernardembden.com/xjs/comclutch/index.htm

Sixto
87 300D
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  #14  
Old 05-04-2011, 02:57 PM
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I have achieved A/C again! Thanks for all the help, guys.

I ended up proceeding with the coil swap. The bad compressor with the good coil I had on my workbench was really, really hard to get apart. Everything that was supposed to come off easily had to be hit pretty hard repeatedly, leaving me to wonder whether I was doing something wrong. I concluded there was no way I would accomplish that again on the compressor on the car without taking it out, so I did. Of course, once out, it came apart 100 times easier than the first one...everything just slid right off. The bad coil didn't look all that bad. And the good coil didn't look all that good. But I put the good compressor back together with the known good coil and a mix-n-match of the better looking of the two pulleys and clutches. And Voila! Works perfectly. Thanks again!

Willis

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