BigMattyD Posted June 2, 2011 Share Posted June 2, 2011 Hi everybody! Recently, the AC compressor clutch will operate for a while, but after 20 min of driving, will fail to engage. The clutch is getting the +12 v signal to engage, and sometimes it works, sometimes it doesnt. If I pull over when this happens, and lightly tap the front of the compressor with the wooden end of my hammer, it will reengage and work properly, so I know the magnet is still operating. When I test the clutch on a stopped engine, using a +12V jumper to the clutch, it engages, and I can cycle it on and off again. The main thing I notice is a lot of brown rust dust around the compressor. I believe the plate is worn to where the clearance between the plate and clutch is too large. The FSM states the gap when open should be 0.45 mm, and on mine, it is about double that at 0.85 mm. I think that would be enough to cause an intermittent engagement. I am about to pull the front plate off the compressor and see if there are spacers underneath it that can be removed to tighten the clearance. I just want to know if anyone has experience with this and can tell me if there are shims or spacers that I can remove to bring the plate closer to the magnet wheel. I disassembled the compressor clutch and pulley on my 1996 Legacy to replace the pulley bearing, and I think i recall a set of spacer washers. But I am not sure about the more modern era compressor clutches. Matt Quote Link to comment Share on other sites More sharing options...
nipper Posted June 2, 2011 Share Posted June 2, 2011 The brown dust is normal on an older subaru clutch. Why did you not go to the very first thing to check and not the very last. KISS (keep it simple -----) You are low on refrigerant, as you have a leak someplace. The AC has two pressure switches, one low and one high. They both have to see normal pressures to operate. You have low refirgerant. The refrigerant is liquid at first, as it gets hotter it expands and will not become liquid again due to a lack of refrigerant. If it was a clutch issue they usually don't engage at all. The fact your does (especially for 20 minutes) says it is fine. Quote Link to comment Share on other sites More sharing options...
BigMattyD Posted June 2, 2011 Author Share Posted June 2, 2011 Nipper: The Clutch is still getting the signal to engage, even when it is not working. When I tap the front plate of the clutch, it will re engage and stay engaged. Initially, I thought it was a pressure issue, but the high side and low side pressures are within the normal ranges. The clutch is definitely being commanded to engage, but it is intermittently actuating. I am thinking a weak magnet coil, that gets worse when warm, or that the distance between the plate and the coil is too great to reliably function. I know the brown dust is common on these compressors, as it appears to be product of wear between the clutch plate and disc, and that is why I measured the actual gap between the plate and disc and found it to be well outside specifications. I'll update with any further info. Matt Quote Link to comment Share on other sites More sharing options...
BigMattyD Posted June 5, 2011 Author Share Posted June 5, 2011 (edited) Ok, I removed the compressor clutch disc and removed the spacer washer. After replacing the disc, the clearance is much better. It seems to be working now, but only time will tell...:-\ I guess I should plan to replace the compressor sometime soon, as I am sure that eventually it will wear out again. Hopefully, it will get us thru the summer... Thanks to ferret for his post on another thread re: the failure of some of these types of clutches: Quote: "Now to the other I have seen. A/C seems to work, but on VERY HOT days, or after using it for a while, it just stops. What's happening here is the CLUTCH is no longer engaging. ( usually the ZEXEL Compressors ). The clutch IS getting the 12v to engage, but with the heat, AND PREVIOUS WEAR, the clutch gap had increased and will no longer engage. Let it cool off and like magic, it works again. When failing and at an idle, you may try to 'carefully' pushing the front plate with a piece of wood ( my choice ) and CLANK, the compressor engages. 2 options here, Replace the compressor. I suggest NEW, I would not use a Used one because the clutch on these DOES wear and like buying a used tire, a used compressor already has wear on it. This option also requires vacuum/charge of the system. Please Note, Zexel supplies to its vendors ( Subaru included ) the compressor/clutch as an assembly. They do not supply clutch replacement parts. The other, is buying/borrowing a clutch removal kit ( usually $50 and up ). Remove the clutch. Clean both sides of the clutch surface. DON'T SAND OR ROUGHEN them. Remove a shim or 2 from under the center bolt mount to get the .0011 to .0015 clearance between the clutch face and pulley. I really suggest getting the tool for this. By just removing the 10mm center bolt, the clutch is pressed on and does not easily come off. Prying on the edges of the clutch will bend and destroy it resulting in replacing the entire compressor." Matt Edited June 5, 2011 by BigMattyD added quote from ferret Quote Link to comment Share on other sites More sharing options...
nipper Posted June 5, 2011 Share Posted June 5, 2011 i will file this in my mind. Used compressor is much better for the wallet then new. i would price new vs used and a new clutch. Quote Link to comment Share on other sites More sharing options...
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