2000 Ford Diesel Superduty
A/C Compressor Clutch
Air Gap Setting


Like any device with clutch plates, there is a wear factor.  In this case, the "air gap" gets wider.  Eventually, the air gap becomes so wide that the electro-magnetic coil that pulls in the clutch plate can no longer do its job, and the air conditioning compressor (Ford FS-10) no longer comes on, resulting in no cold air. 

In reality, before it completely fails, the clutch becomes intermittant, and you get cold air sometimes, and sometimes not.  Usually it works upon initial turn-on for a couple of minutes, then loses the ability.  I suspect this is due to the difference in magnetism with slightly different amounts of current passing through the magnet's coil.  Cold wire has lower resistance, thus it's easier for current to pass, thus more current, and more magnetism to overcome the greater air gap.

There's an extremely easy way to fix this problem in a Ford SuperDuty or Excursion with this problem, and I've detailed it below.

Click on the photos to enlarge them.

beads

Tools and Materials

8mm 1/4-inch-drive socket
1/4-inch-drive ratchet
Set of "feeler guages"
Thickness micrometer, 0 to 1"
Flat file, medium-fine (or a set of compressor air gap shims, see below)
Blue (low strength) LocTite

beads

Check the Compressor Air Gap

comp_sm

Click on the photo at left to enlarge it.  The compressor is located right behind the "radiator cap" on the plastic coolant degas bottle. Notice the "air gap".

 

feeler

You need to know what the air gap is currently at.  Measure it with a set of "feeler guages". If the gap is wider than the thickest guage (usually .025"), use more than one, and just add the amounts of thickness to get the total. Write this number down, and subtract .020" (twenty thousandths).  The remainder is the amount you need to remove from the existing shim or shims between the clutch plate and the end of the compressor shaft.

 

ratchet

You will need an eight millimeter, quarter-inch drive, socket and ratchet.

If you don't already own a set like this, just go buy one! You're going to need it over and over again, for many other jobs.

 

clutch

To remove the clutch plate, turn the ignition switch to "On" (not "Start"), and the air conditioning also to "On".  This pulls in the clutch so that the serpentine belt holds it all from turning. Notice in the photo at left that the previously-seen air gap has disappeared. Again, click to enlarge. This bolt is a regular, right-hand thread, and when you take it out no refrigerant will escape. If you ever need to replace this bolt, it is a 6mm x 1.0 x 20mm bolt, and looks like this:

 

plate

Shut off the air conditioning switch and ignition switch. The air gap will re-appear. Carefully slide the clutch plate forward toward the de-gas bottle. Be careful to not drop any shims.  It (or "they" if more than one) will be either stuck to the end of the compressor shaft, or down inside the splines of the clutch plate. Carefully remove and measure the thickness of it (or them) with a micrometer. Remember the amount from above that must be removed?  Subtract that amount from the thickness of the shim(s).  That is the final thickness you want after filing or using new shims. File it thinner, or use different shims, to obtain the proper thickness.
Note: When you have this apart, you may see a large snap ring on the compressor's "snout". It retains the pulley onto the compressor. Do not remove the snap ring unless you are going so far as to completely replace the clutch pully assembly, and that's not within the scope of this fix.

shims


Ford makes a shim kit available, with thicknesses of  .024", .030", .036", .042", and .048".  It's Ford p/n YF-1800-A.  AutoZone can also order you a shim kit. It's their part number MT0986. Hint: The AutoZone kit is much cheaper than the Ford kit is.

 

gap

 

Re-assemble using the reverse order of the above. Only snug down the center bolt for now, don't tighten it down completely.  You DID turn on the system to pull in the clutch didn't you?  Turn off the system and re-measure the air gap you now have.  It won't be exactly .020", it never is.  However, it should be close, within .003" or so, in either direction. Once you know you have it almost perfect, remove the bolt and apply some BLUE LocTite to the end three threads of the bolt.  Re-install the bolt and tighten snugly.  The LocTite will prevent the bolt from working its way loose and falling out.  That results in bad things happening, so use the stuff!

beads

Testing the Results

Start the engine, but leave the air conditioning off.  Verify that the clutch plate is NOT turning.  If it is, you have too little gap, and the compressor CAN'T shut off.  This will damage the system in less than a minute, so DON'T leave the engine running if you see the clutch turning at this point in time!

If it's not turning, start the air conditioning and verify the clutch has engaged the compressor. 

Turn the system back off and verify the clutch is no longer turning.

beads

Does it Work Properly?

If so, congratulations! You've successfully re-adjusted your compressor's clutch to the proper air gap specifications.  It will last a lot more years before you need to do it again.

If not, you have additional problems that are not covered by the scope of this article.  Further testing is necessary, but "air gap" isn't a problem factor now.

beads

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Last updated 07/29/13

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