So, I think my A/C compressor clutch is bad (2007 Outback Wagon 2.5i Basic).  I'd like some comments about whether my diagnosis is reasonable and any "gotcha's" in the replacement process.

 

I noticed my A/C quitting - intermittently at first then as time went on less and less often.  It seems like it is more likely to work when the engine is cold, first thing in the morning.

 

When the air works it cools well, but it doesn't usually run very long before it stops.

 

I thought it might be low on refrigerant, but I put a gauge (borrowed my dad's cheap one from a refrigerant can) and the low side read 150psi, so I didn't put in any refrigerant and looked elsewhere.

 

When it doesn't work the clutch is does not spin.

 

Once when it was not working, I measured the voltage to the clutch coil and it was plenty - I think it was around 14 volts - but that was no load.  The coil resistance measured 20 ohms, and from what I read several places on the internet the coil should be more like 3-5 ohms (really, the thing pulls 4 amps?).

 

Any other diagnostics I should try before I order a clutch kit?  It seems Subaru doesn't sell the clutch separate from the compressor but I do see an aftermarket kit on amazon and the coil by itself on eBay so there are some sources.

 

Am I likely to have a pressed on pulley and have a hard time getting the pulley off with the compressor in the car?

 

Thanks.

Clutch is probably ok.

18-20 ohms is normal for most clutch coils.

 

The coil has become weak with age though. Common issue on these.

The easy fix is to remove the clutch face and remove a shim washer to tighten up the clearance of the clutch. This usually pulls the clutch in enough that it starts working properly again. Just make sure you still have some clearance between the clutch and pulley when the clutch is reinstalled. Don't need much, just enough that it doesn't drag.

 

Best way to test if it is the coil is with the engine running, run the AC until it stops working. Check voltage at the coil to be sure it's being powered (ecu is telling it to run) and tap the face of the clutch with a screwdriver handle.

Edited July 20, 20178 yr by Fairtax4me

read here; http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/43428-diy-c-air-conditioning-leak-refrigerant-repair-5-less-15-minutes-less.html

 

also, I have read once of the clutch relay being weak/dropping-out.

Edited July 20, 20178 yr by 1 Lucky Texan

Clutch is probably ok.

18-20 ohms is normal for most clutch coils.

 

The coil has become weak with age though. Common issue on these.

The easy fix is to remove the clutch face and remove a shim washer to tighten up the clearance of the clutch. This usually pulls the clutch in enough that it starts working properly again. Just make sure you still have some clearance between the clutch and pulley when the clutch is reinstalled. Don't need much, just enough that it doesn't drag.

 

Best way to test if it is the coil is with the engine running, run the AC until it stops working. Check voltage at the coil to be sure it's being powered (ecu is telling it to run) and tap the face of the clutch with a screwdriver handle.

 

I did read the voltage on the harness (unplugged the coil and read the connector) and open circuit the coil connector was getting decent voltage.  The voltage would come and go as the A/C button was turned on and off.  So it seems to me the control circuitry is asking the compressor to run.

 

I tapping the front of the clutch did not produce any effect - it did not engage, or try to engage as far as I could tell.

 

I think my next steps will be to one or more of the following:

* Check coil voltage with the coil in the circuit to detect excessive voltage drop in the supply relay or wiring.

* Bypass the supply wiring with a fused line straight from the battery and see if the clucth engages under those circumstances.

read here; http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/43428-diy-c-air-conditioning-leak-refrigerant-repair-5-less-15-minutes-less.html

 

also, I have read once of the clutch relay being weak/dropping-out.

 

(short version)

Bingo.

 

(Long version)

My meter was acting funny so I replaced the batteries.  Now it says the coil is 4.5 ohms.

I jumped the coil to the battery and the clutch clicked in (but engine wasn't running)

Looked at the my Haynes manual for wiring diagrams to locate the relay.  Somewhat helpful but the diagram shows a different relay block than I have.

Finally found the relay by.....um....actually reading the cover to the relay block under the hood.

Removed AC relay, took voltage readings to verify the pressure switch was supplying power and things looked good.

Swapped the A/C relay with the second radiator fan and, I now have working A/C and non-working radiator fan.

Alas, none of the relays in my junk pile match (mostly they are from my '94 Loyale parts car), so I had to order one from the local parts store.