Replacing the AC compressor clutch

Discussion in 'SN95 4.6L Mustang Tech' started by COramprat, Feb 8, 2006.

  1. I've now done 2 of these and have seen more than a few threads of people complaining about theirs. I've been meaning to do this for a while so I decided to put together this how-to now so you can do-it-yourself.

    Tools required:
    -10mm (8mm) sockets/box wrench.

    -AC pulley puller ( I purchased one from Sears-Craftsman, but Autozone has them to rent)

    -1/2 inch socket wrench or breaker bar

    -Strap wrench

    -Snap Ring Pliers

    -Rubber Mallet


    -Block of wood.


    1. Disconnect the battery (every job begins with this tidbit... ;) )

    2. Disconnect the AC wiring harness from the clutch assembly.

    If you don't have a strap wrench:

    3. With the serpentine belt still in place (to minimize movement), loosen the center bolt(it's either 10mm or 8mm). You may need to jam the pulley with a screwdriver to keep it from turning. DO NOT REMOVE THE BOLT YET, LOOSEN ONLY.

    4. Once the bolt is loosened, remove the belt with the 1/2 inch socket wrench or breaker bar inserted into the tensioner.

    With a strap wrench:

    5. Hold the pulley in place with the strap wrench while loosening the center bolt with a 10mm (8mm) socket.

    6. Once the bolt is loosened, remove the belt. (Unless you have already done so when using the strap wrench)

    7. Remove the bolt and slide the pulley cover off. There is a spacer inside of the cover. Hang on to it to reuse or compare it to the new spacers if your new clutch includes them and you will replace with one like.

    8. With the snap ring pliers, remove the snap ring from the compressor shaft.

    9. Take the AC pulley puller, attach it to the pulley per the instructions with the pulley. Slowly remove the pulley.
    (NOTE: There is something directly in front of the pulley (don't remember what it is) so be careful not to bind the puller against it. You can loosen the part that is in the way and move it some.)

    10. Take a large screwdriver and gently but with force remove the coil from the compressor housing. Loosen a small amount, then move to the opposite side, a little at a time.

    11. Now take the new coil and slide it onto the compressor housing...making sure the coil electrical connector is lined up with the indention on the housing. Take the rubber mallet and seat the coil. It should slide right on but if you need more force get a 4x4 block of wood and a hammer to tap it into place. The coil HAS to seat perfectly onto the housing or the pulley will not slide on. Examine the the area where the coil seats from top to bottom. Make sure it is completely flush with the housing. No gap between the coil and compressor housing.

    12. Take the pulley and slide it onto the shaft. It should go right on without much force. If it will not, check the coil to make sure it is properly seated. You can take the hammer and tap into place.

    13. Replace the snap ring.

    14. Use a feeler gauge to measure the spacers for the air gap (generally between .018 and .030) or match the old spacer with the new and drop it into the new pulley cover. Make sure it lays flat inside the shaft so that the bolt will slide through.

    14. Slide the cover unto the shaft and replace the bolt. Use the strap wrench to hold the pulley while tightening.

    15. Replace the serpentine belt.

    16. Reconnect the AC coil harness and the battery.

    17. Crank the car. Make sure the AC is off and check the compressor. The pulley should turn but the compressor should be off. Now turn on the AC and compressor should run. If not or if it is hesitating you may need to try another spacer. Rule of thumb is 1/8 (.015-.025) of an inch is needed between the coil and the pulley cover for the compressor to operate but if you match the spacer with the old it should be OK.


    This was done from memory and I should have taken pics when I did these but this will give you a general of how to replace it. If anyone has any input feel free to include it.
  2. very good but the only problem with the instructions is your not measuring the air gap just reusing the old shim.

    i find a match book cover to be perfect for measuring the air gap if it slides thru with slight drag thats perfect.

    if somebody is interested i can look up the exact specs for air gap. but i have always did the matchbook trick instead of get out feeler gauges.
  3. Cool...I had the wrong spacer in mine at first and the compressor stuttered. I pulled the pulley cover and matched the old spacer with the new and it worked.

    Are you measuring the gap between the pulley and the pulley cover?
  4. I posted this a while back but here it is again.

    Service and Repair


    1. Remove the A/C compressor.

    1. Remove the bolt.
    1Hold the A/C clutch hub with the special tool.2Remove the bolt. [​IMG]

    1. Remove the A/C clutch and the A/C clutch hub spacer.
    1Thread an 8 x 1.25 mm bolt into the A/C clutch to force it from the compressor shaft.2Lift the A/C clutch and the A/C clutch hub spacer from the compressor shaft. [​IMG]

    1. Remove the pulley snap ring.

    1. Remove the A/C clutch pulley.

    1. Remove the A/C clutch field coil.
    1Note the location of the A/C clutch field coil electrical connector.2Install the special tool on the nose opening of the A/C compressor.3Install the special tool.4Remove the A/C clutch field coilCAUTION: Do not use air tools. The A/C clutch field coil can be easily damaged.

    1. Clean the A/C clutch field coil and pulley mounting surfaces.

    1. Install the A/C clutch field coil.
    1Place the A/C clutch field coil on the A/C compressor with the A/C clutch field coil electrical connector correctly positioned.2Using the special tools, install the A/C field coil.CAUTION: Do not use air tools. The A/C clutch field coil can be easily damaged.


    1. Install the A/C clutch pulley. NOTE: The A/C clutch pulley is a tight fit on the A/C compressor head. It must be correctly aligned during installation.

    1. Install the pulley snap ring with the bevel side out.

    1. Place one nominal thickness A/C clutch hub spacer inside the clutch hub spline opening.

    1. Install the A/C clutch.

    1. Using the special tool, install the A/C clutch hub retaining bolt.

    1. Measure and adjust the clutch air gap by removing or adding A/C clutch hub spacers.
    2. Install the A/C compressor.
  5. nic pics right out of the ford manual. alli use for tools when i do them is, a 8 mm socket and 1/4 rachet, rubber hammer, snap ring pilers and a matchbook.

    but nothing against using the right tools. at my work i will never be able to find them.
  6. What are the symptoms of a bad a/c compressor clutch? My a/c almost sounds like diesel (rattle) when it cycles on, but it still works good, cools the car just fine.
  7. Awesome thread :nice:

  8. that could be the clutch. take a listen to it and see if thats where the noise is coming from.
  9. With the car off reach down and tap on the front of the pulley. If it rattles around then the bearing are gone/going. The clutch is probably fine but the bearing are what wears out. Might as well replace the whole thing.
  10. If my AC compressor sudenly shuts down even though the ac is on. When I'm driving. If I rev the engine or shut down the ac and turn it back on it starts again. Does that mean that my clutch is bad?
  11. ^^ That sounds like you are low on refrigerant. If it is cycling constantly and not getting cool, it is either low on r134a or the pressure switch is going bad.
  12. better info...

    Some of the above is not quite right. Here's the corrections:

    (1) you do _not_ reuse the old spacer when installing the new compressor clutch. Any good kit (and I have done several) comes with a set of 5 shim/washers of varying thickness. You have to trial-and-error this to get the air gap set properly. Too tight and the clutch will drag and overheat/wear out, too loose and it can't properly engage, and it will slip/overheat/wear out. It has to be right. Generally something between .018 and .030 but the clutch you install might have different numbers. Go by those. You need a good feeler guage to set this properly

    (2) There are three parts to the clutch. The coil which is pressed on to the compressor housing, the bearing which is a tight fit on the compressor shaft, retained by an internal snap-ring and this part includes the pully for the serpentine, and finally the clutch hub that bolts to the compressor shaft and presses against the pully hub when the clutch is engaged. When the clutch goes, it can go in several different ways. The bearing can seize, which will break the belt, or can prevent the motor from cranking by preventing it from turning over. If this happens, you are not going anywhere until it is fixed. The clutch can wear out or can overheat. When this happens you can usually grab the center of the clutch and it will move as the rubber bushings that absorb the shock of engaging melt away and let the friction plate rattle. If this happens (the rattling when you try to move the front disc on the clutch) the bearings are still fine, but the clutch will not properly engage, and it will make a racket and probably will smoke some too. You will have no A/C and the A/C should be turned off until it is fixed. If you try to let it run, the overheating can pass on to the compressor shaft, and the front seal will melt and leak. In a significant number of cases, this happens when the compressor clutch fails, in fact. At todays prices, the clutch at Advanced is about a hundred bucks, and a complete compressor is only $166. Replacing the whole thing is a lot safer in terms of eliminating future problems.

    The center hub comes off easily once the center 8mm bolt is removed. It is just a slip on fit onto a splined shaft. The bearing/pulley is not that tight a fit, although once the bearing goes, the race can spin, and the resulting metal transfer can make it a bit harder to pull off. The coil comes off easily enough using a couple of small pry-bars. A puller can damage it if you are not careful, causing a short and a different type of failure. Installing the clutch is easy enough, the most time-consuming part is fooling with the spacers to get the air-gap properly set. If you don't feel like you can do that properly, then don't start the process at all as the wrong gap can easily ruin the clutch, and even worse, burn up the front seal on the compressor.

    Using the original spacer to guess about the air gap is about is safe as installing new rear end gears and using the old shims without checking anything. At best you get a whine, at worse, ruined gears.
  13. Good points Bob...

    Yes...the kit I had came with new shims. I just compared what was in there originally with the new ones and everything was fine. Feeler gauge would be optimum but I didn't have one. It is obvious when the air gap isn't correct since the compressor with not work at all or will cycle on and off rapidly. At least that is what I found in my trial and error. I changed the step to reflect your point.
    I have put a good 70K miles on mine since the swap with no issues.

    I'd have to look at mine again to determine what the obstruction is but there is a module of some sort directly in front of my AC compresser as was the '01 Bullitt I helped a friend fix. The particular puller I have was a tight fit and I just loosened the bracket to provide some clearance.
  14. hate to bring up old threads but needed some additional info than what was provided. My 94 GT just began having an issue with its ac. It still blows cold but when the compressor cycles on it makes a fairly loud rattling noise and when the clutch disengages it goes away. It's also quiet when the AC is off and the pulley free spins and no noise. At first I was thinking clutch but it seems to cycle on and off properly with no issues so I was thinking the bearing on the pulley. Trying to keep this as an inexpensive fix and would rather not have to pay for a new compressor and go through the hassle of evacuating and recharging the refrigerant. Anyone have any suggestions as to whether it's the ac clutch, the pulley bearing or needs a new compressor? :shrug: