Diagnosing A/C... should the compressor turn easily by hand?

[outback_97]

Hi, my 97 OB's A/C doesn't work.  The fan works fine but it just blows ambient temp air.  The compressor clutch doesn't seem to be engaging.  When I compared it to my wife's 03 Impreza, turning the front part of the compressor offers quite a bit more resistance in the working A/C (the '03).  On my '97 it turns with no resistance at all.

 

Just trying to figure out if this diffrence indicates a problem, or if it's normal for them to spin freely but not engage.  Not sure where to begin with diagnosing the A/C.  Thanks!

[Fairtax4me]

Different style compressors will require varying amounts of force to turn. Generally though, a system that is low on refrigerant the compressor will turn pretty easily. Where-as one that is fully charged will have more resistance.

 

Low refrigerant is the most common culprit. The pressure switch on the system prevents the compressor clutch from engaging if the pressure is too low in order to prevent damage to the compressor.

[Rooster2]

Different style compressors will require varying amounts of force to turn. Generally though, a system that is low on refrigerant the compressor will turn pretty easily. Where-as one that is fully charged will have more resistance.

 

Low refrigerant is the most common culprit. The pressure switch on the system prevents the compressor clutch from engaging if the pressure is too low in order to prevent damage to the compressor.

Same thought. I think your system needs recharged. If leaking refrigerant, then the leak will need to be fixed.

[idosubaru]

+1 usually low refrigerant.

 

while the system is dead replace the orings where the hoses bolt to the compressor - those are the most common leakage points.  replace schrader valves while you're at it.

 

recharge

[outback_97]

Thanks guys. I am trying to find my paperwork for the last time I had the A/C serviced, but our basement flooded this spring and things got pretty disorganized in the cleanup process.  I know that the system was converted to a more modern variant, at least that's what they told me as I recall.

 

I looked at those $30 DIY recharge kits that connect to the low pressure side, but in reading reviews it sounds like the gauges are often wildly inaccurate.  If it just needs more refrigerant, would you recommend even trying one of those?

 

The next DIY step up from that I think would involve buying an A/C pressure gauge set from Harbor Freight.

http://www.harborfreight.com/a-c-manifold-gauge-set-92649.html

 

But it sounds like to use that correctly, one really needs a vacuum pump and that's another thing that I don't have.  I'm trying to minimize cost sunk into this since I'm considering selling the car this winter.

[Rooster2]

Thanks guys. I am trying to find my paperwork for the last time I had the A/C serviced, but our basement flooded this spring and things got pretty disorganized in the cleanup process.  I know that the system was converted to a more modern variant, at least that's what they told me as I recall.

 

I looked at those $30 DIY recharge kits that connect to the low pressure side, but in reading reviews it sounds like the gauges are often wildly inaccurate.  If it just needs more refrigerant, would you recommend even trying one of those?

 

The next DIY step up from that I think would involve buying an A/C pressure gauge set from Harbor Freight.

http://www.harborfreight.com/a-c-manifold-gauge-set-92649.html

 

But it sounds like to use that correctly, one really needs a vacuum pump and that's another thing that I don't have.  I'm trying to minimize cost sunk into this since I'm considering selling the car this winter.

For what it is worth, I bought the A/C gauge set from Harbor Freight a couple of years back. The set seemed okay, but it seems designed for commercial use, not for the DIY kits, or individual 13 oz cans available at an auto parts store. Also, it was Chinese manufactured, and the directions for gauge use were very poorly written. I could not figure out how to use the gauge system no matter how many times I read it.

 

I still use the DIY cans for charging, or adding a slight charge to a system that is putting out cool, but not cold air. IMO, my rule of thumb is to add one can if going from cool to cold, or use 2 cans if the system is totally empty of refrigerant. I have some further advise, but am under a time restraint at the moment. Drop me a note if interested at fish6525@yahoo.com...........Rooster2

[1 Lucky Texan]

I kinda regret buying my gauge set from Amazon - it did help me a little but, I'd have been better off just doing what is recommended in the Forum.

 

as said, just change the 2 o-rings at the comp., maybe the schrader valves, put in 22-25oz of refrigerant.(or w'ever is recomm. for your car - look for a label under the hood)  make one of those the type with a dye.

 

then, drive. If you have problems, probably best to take to a pro. Tell him what you did and let him go from there. He can check for the dye, recover refrigerant, test pressures and otherwise diagnose the system.

[keith3267]

I had a set of gauges from Harbor Freight but the connectors were so poorly manufactured that they did not fit on all the R134 systems that I had.  They were very tight on the ones they fit on and would just not go on some others.  I bought a cheap set from AZ and it fit all the systems but gauges were not very good.  I bought a better set at O'Rielly's and it has worked very well for me.  The good set only cost me about $20 more than the one from Harbor Freight.

 

I would get a set of these gauges if you are comfortable with working on an AC system.  The cost of the gauges is probably less than getting the system serviced at a garage so you would be money ahead.  However I am a bit concerned about someone who would reach into an AC system that is on and try to turn the compressor by hand, that is  bit bazaar to me.

 

There is a relay that turns on the AC clutch.  If you remove the relay and jump the terminals for the contacts, you should see the clutch engage.  If the engine is running, the compressor should start working, but you have to be very careful here, if the charge is too low, you will damage the compressor.  I would put gauges on first.

 

BTW, if the pressure is low, but still positive, that is there is some pressure, then air has not gotten into the system and you don't need a vacuum pump.  The vacuum pump is for systems that are completely empty and air may have gotten in, or the system is opened up.

 

If the system is very low, you should replace the schrader valves.  Some refrigerant will escape, but as long as you get the new valve in quick enough, air will not get into the system. You do not want to remove a schrader valve if the system is pressurized as you could be badly injured.

[outback_97]

I had a set of gauges from Harbor Freight but the connectors were so poorly manufactured that they did not fit on all the R134 systems that I had ...

 

I would get a set of these gauges if you are comfortable with working on an AC system.  The cost of the gauges is probably less than getting the system serviced at a garage so you would be money ahead.  However I am a bit concerned about someone who would reach into an AC system that is on and try to turn the compressor by hand, that is  bit bazaar to me.

 

...

 

Thanks for the reply.  To clarify, I was comparing the feel of hand turning the part of the A/C compressor that you see when looking at the front of the engine. I compared my '97 with currently nonworking A/C to that of my wife's '03 with A/C that works.  I was wondering if that difference in feel could be used to help diagnose the A/C.  They felt different when turning by hand with the engine turned OFF.  I like my fingers too much to stick them that close to belts and pulleys on a running engine!

 

Interesting feedback on the gauges, if I buy a set I will shop around to see what's available besides HF.  Thanks again.

[idosubaru]

Slow down and keep this simple.  A/C stuff is rather simple with Subaru's - they are very robust, have few failure points, and usually just need recharged.  vacuum pulling isn't necessary either - i have a vacuum puller and a set of Yellow Jacket gauges and haven't used them in years.  I've done gobs of Subaru A/C work and it's easy.

 

Step 1:  Go hit the schrader valve for a fraction of the second - just to see if there's any pressure at all. 

if it's busts out fast and some oil comes with it and it made you jump - it's still under nearly full charge.  that will require some follow up questions/testing.

if it barely pssssttt out, then it's basically all drained from leaking - this is the most likely outcome.

 

Step 2:  Take note - are the two hose fittings at the compressor wet at all?  A leak in the hose will pull some oil out with it and show itself by very minor wet marks and debris sticking to the oil. 

if they're wet - replace said hose.

 

I'm assuming it'll be nearly empty of refrigerant - you'll usually hear some residual pressure bleed off, but it's minor compared to a full system.

 

Option 1. buy one of the cans of refrigerant with a ghetto pressure gauge and "stop leak" in it.  fill it.  this is often effective at mitigating leaks.  i wouldn't do this myself, i'd do Option 2 below, but some people just want quick and easy.

 

Option 2  buy same can with the ghetto pressure gauge attached. 

buy one of the "A/C kits' that have all the orings in it.

replace the two orings on the hoses that bolt to the compressor.

add proper amount of refrigerant - two of the normal sized small cans works for all Subarus and i'll even add that without using gauges if it's an empty system.

 

***There is no need to pull a vacuum.  I've done it countless times on Subarus - it's way overhyped by folks that don't know what they're talking about or HVAC people that only know one way of doing it and make mad loot off a public that's terrified of A/C systems.

[Rooster2]

Option 2  buy same can with the ghetto pressure gauge attached. 

buy one of the "A/C kits' that have all the orings in it.

replace the two orings on the hoses that bolt to the compressor.

add proper amount of refrigerant - two of the normal sized small cans
works for all Subarus and i'll even add that without using gauges if
it's an empty system.

 

***There is no need to pull a vacuum.  I've done it countless times
on Subarus - it's way overhyped by folks that don't know what they're
talking about or HVAC people that only know one way of doing it and make
mad loot off a public that's terrified of A/C systems.

 

Grossgary,

 

I took your advise last Spring using Option #2. Your advise was spot on. I had to replace a leaking metal tube line. On a completely empty system, I started by adding about a half can of 134a. I then bled that out thru the Schrader to the atmosphere, thinking this would also pull out a good share of any moisture and atmosphere from the system. (Yea, I know the environmentalist don't like people venting 134a to the atmosphere, but then the same thing happens when your system develops a leak) So, I don't feel too guilty. Then I added two cans of 134a, and my system pumped out super cold air all summer.

 

Yea the gauge on a cheap hose attaching to a can is not terribly accurate, but it doesn't need to be.  To me "close" on correct amount is good enough, and I bet I have serviced some 50+ cars this way, with no problems.

[Fairtax4me]

It doesn't hurt to have a guage set IF you plan to do AC work on a lot of cars. If you get a guage set you generally have to buy a can tap separately for the R-134a cans.

A guage set certainly isn't necessary to recharge a system though. You can buy one of the recharge kits at the parts store. Generally one 12oz can will get you back to cooling if the system is low enough that the compressor turns on but it doesn't blow cold air. If the compressor doesn't turn on, you probably need 16-18oz.

A 12 oz can will usually do it for the newer systems that only hold 17-19 oz.

[outback_97]

OK, an update.  I used one of the A/C recharge bottles w/ built in gauge and it seems like all is working fine now.  How long it will keep working is hard to say.

 

The compressor started turning after I added some of the refrigerant.  Then I continued adding more until I was in the proper range according to the built in gauge.  The 18 oz bottle still has some in but I neglected to weigh it beforehand so it's hard to say how much material was used.  I'm guessing I used 50 to 75% of the contents of the bottle.

 

Thanks again for all the great advice!  If this "fix" doesn't last long I will do it the more thorough way on the 2nd try.  But for now it all seems to be working great.

[idosubaru]

like we all said - probably low on refrigerant.

 

which means it had a leak.

 

leaks are usually the orings on the compressor.  replace those if you need to attempt a fix.

[Cosstreck18]

Hi,

i just replaces my compressor. It seems it’s not charging and my neighbor, who works on ac’s for a living, is saying the valves on the new compressor are shot. So, i vacuumed the lines and tried to turn the compressor clutch with my hand, I got absolutely ZERO resistance. The lines are empty with no air or refrigerant in it. Shouldn’t I get a little resistance?

[forester2002s]

The AC compressor-clutch doesn't activate unless the signal-wire has voltage applied to it (this happens when the refrigerant is at the correct pressure).

If the compressor is removed from the engine, the belt-pulley should spin freely.