Not for a diesel but where else but here will I find as much help on A/C
Anyway a friend has a 89 Porsche 911 with the nippondenso compressor running on r-12.
Believe it or not r-12 is on sale here this month for $19.97 pound! So I was going to try and see what his problem was today. When he stated the car and fired up the A/C the clutch did not kick on. Figured it was low pressure as he said he had a very slow leak, needed a shot about once a year or so. I hooked up the gauges and had an equal pressure on both sides of 135 pounds so I thought it strange compressor the system would not kick in. When I ran a 12v hot wire to the clutch I got nothing. On any other compressor I have worked on if you put 12v to the clutch it would at least kick on. I am thinking a bad clutch, or is there something on this setup that would still keep the clutch from kicking in?
BTW dealer wanted $1400 for the clutch, $2890 for compressor and clutch both

Oh and when I do this system it will be all r-12 since the price is now reasonable

I've been saying for quite some time that R12 prices will come down as the demand goes down. The cars that require it are hitting the wrecking yards every day, so demand goes down every day.

If you are jumping 12V to the clutch and it does not kick in, the problem is the clutch. It is bad, has a bad ground, your hot wire is not indeed hot or something.

As a precaution, with engine off, turn the compressor by hand to ensure that it rotates freely.

Good luck,

Thanks Larry.

I know I had 12V as I had a clamp on the + side of the battery and got a good spark when I tried an engine mount bolt. The thing turned fine, no noise when running the engine the clutch just would not kick in but you could turn the clutch part by hand no problem and it felt tight with no crap inside.
Also on the price of r-12. Last month at the same McParts place a can of 12 was $49.95 What he aid yesterday was the sale is for this month only and then it goes back up to the old price. I wonder about that.

If you've got a DVM check the resistance of the clutch coil. Should be 3-4 ohms on a healthy coil. Infinite resistance would of course be a problem. Check directly on the compressor to eliminate the wiring harness as a potential problem.

Here's an article that discusses rebuilding a 10P15C on a 911. It's more involved than you need, but it does show how to remove/install the clutch and coil as part of the process. I've done this and it isn't very difficult, just have a decent selection of snap ring pliers handy.

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

- JimY