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A/C goes off, returns with restart


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22 replies to this topic

#1 sajara

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Posted 22 August 2009 - 11:07 AM

Hi all,

I've read a zillion A/C posts on here, but didn't find anything quite like my situation. My A/C goes off (starts blowing warm air) about five minutes or so into a car ride. If I switch the engine all the way off and restart the car, the A/C begins working again, but only for about five minutes or so. When this issue first arose, the A/C lasted a lot longer before going out; now we are down to a few minutes.

I recharged the A/C, and the freon was really low, but that did not stop the problem.

Any ideas?

Thanks!!

--Natalie
2002 LLB Outback

#2 Fairtax4me

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Posted 22 August 2009 - 11:27 AM

I'm gonna guess that its a faulty pressure switch, or compressor clutch relay. Both of those are fairly easy to test with a multimeter. To do a quick test of the relay, just swap it with another relay in the under hood fuse panel like the fan relay and see if it starts working normally again.

#3 nipper

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Posted 22 August 2009 - 11:57 AM

Ild check the pressures first, you may be borderline low on your pressures.


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#4 sajara

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Posted 23 August 2009 - 12:55 PM

Great -- I will follow those suggestions. Where is the pressure switch located on a 2002 LLB Outback? Thanks!! :)

#5 Scoobywagon

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Posted 23 August 2009 - 06:19 PM

Low pressure would not cause this problem. If low refrigerant pressure was the problem, it wouldn't come back on at restart. It would still be low.

As for the pressure switch...its usually located on the receiver/dryer, but not always. I'd have to look up the application at work. I don't feel that is your problem either. Those switches are very simple. They either work or they don't. They don't care whether the car is running or not.

have you put a set off guages on the car? If not, how did you determine that your refrigerant was low? If you have, what were the high-side and low-side pressures with the car running?

Here is my thought...If the system builds up too much pressure, it will turn off so as to keep the compressor from eating itself. If your car has the automatic climate control system, and most of the LL Bean cars that I've seen do, the computer may be seeing the high pressure and turning off the compressor. And for safety reasons, it may be keeping the compressor off until you restart when pressures are normal again.

The other possibility that occurs to me right this moment is that your climate control system is having some sort of problem.

Of the two, I'd much rather have the first problem. That should be pretty straight forward to track down and most of the parts you'd need to correct any of the several causes of high pressure are inexpensive. The CCS problem is easy enough to track down, but that control unit is expensive!

#6 sajara

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Posted 24 August 2009 - 06:23 PM

Well, when we first starting trying to figure this out, we checked the pressure by putting a gauge on as part of one of those DIY a/c rechargers from a parts store, although I couldn't tell you exactly what the pressures were. I know everything was low, and we filled it to the proper amounts.

Today we went to check again so that I could report on the pressure, but it started making a really weird sound and the compressor cycled on & off like maniacally fast. Since I'm headed on a road trip Wednesday, I dumped it off at a local shop.

They called & said it was fixed; we had overfilled it this morning so the pressure was too high, so they normalized that. Also said there was a bad valve (Stracher valve? something like that), so they replaced that. I picked it up, drove it around, and. . .same problem.

I took it back in & they looked some more. Now they believe they have identified a loss of power to the relay. It was about closing time, so I'm to bring it in again tomorrow morning to see if they can determine the cause of the power loss.

I will keep you posted, and thanks for all the ideas & guidance!

#7 nipper

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Posted 24 August 2009 - 07:22 PM

Well, when we first starting trying to figure this out, we checked the pressure by putting a gauge on as part of one of those DIY a/c rechargers from a parts store, although I couldn't tell you exactly what the pressures were. I know everything was low, and we filled it to the proper amounts.

Today we went to check again so that I could report on the pressure, but it started making a really weird sound and the compressor cycled on & off like maniacally fast. Since I'm headed on a road trip Wednesday, I dumped it off at a local shop.

They called & said it was fixed; we had overfilled it this morning so the pressure was too high, so they normalized that. Also said there was a bad valve (Stracher valve? something like that), so they replaced that. I picked it up, drove it around, and. . .same problem.

I took it back in & they looked some more. Now they believe they have identified a loss of power to the relay. It was about closing time, so I'm to bring it in again tomorrow morning to see if they can determine the cause of the power loss.

I will keep you posted, and thanks for all the ideas & guidance!


NEVER EVER EVER rely on those gauges from a DIY refill kit. they are crap. They get more people in trouble with thier AC system. Also to properly diagnose an AC system you need to read the low pressure, high pressure along with air temp. For those pressures you need the proper gauges.


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#8 ferret

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Posted 25 August 2009 - 05:54 AM

Natalie,

Read the following similar post and see what I have found to be the culprit on page 2 post #11. Yours, and many others, are falling into this age.

http://www.ultimates...ad.php?t=102171

#9 sajara

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Posted 25 August 2009 - 06:57 AM

Nipper -- well, good to know! I guess what else would I expect for $29.99??

Ferret -- thanks for the cite. After reading that whole thread, I think I may decline any work on the system if the shop's first plan doesn't involve the relay!

Dropped it off this a.m.; will keep you posted.

#10 sajara

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Posted 25 August 2009 - 12:01 PM

Just got a call from the shop. They have identified the revolution sensor on the compressor as the culprit, stating that it keeps going out. Cost of replacement part and labor is $296.

Does the diagnosis sound logical? And the cost reasonable?

Thanks for any input!!

--Natalie

#11 hohieu

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Posted 25 August 2009 - 01:12 PM

There's really no such thing as a revolution sensor -- only a wire that provides power to the magnetic compressor clutch. The pressure sensor closes the circuit to the clutch when the pressure falls within a certain range.

Diagnosis of AC issues takes some time, but actual replacement of the pressure sensor takes 5 minutes plus the time it takes to capture, evacuate, and recharge the system.

#12 grossgary

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Posted 25 August 2009 - 03:11 PM

If that sensor is really bad I would replace it with a used one. They almost never fail, not worth "new prices" and they're easier to replace than changing oil. Super easy.

That price is really high for a part that almost never fails and takes 2 minutes to replace, but the problem is they are pricing a new one.
A used one would probably cost very little, there's probably tons of folks on here that have one they'd sell. I even have a few lying around.

#13 Scoobywagon

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Posted 25 August 2009 - 05:22 PM

I'm not real sure what they are talking about when they refer to a "revolution sensor". HOwever, I am looking at the diagram and there DOES appear to be an electrical connection other than just the power for the clutch. It looks like it might be a little inductive pickup to tell the computer if the compressor is running or not. That way, if the compressor were to seize, the computer can turn off the ac so as to minimize other damage. It protects little things...like the belt that runs your water pump. This part is, in fact, called the "revolution sensor". The Subaru Part number is 73190AE000. It retails $120. Labor looks to be about an hour or so. The diagram is a bit unclear as to what all has to come off to get to this thing. So at my shop, you'd be looking at about $200 to change the sensor, plus $78 for evac/recharge plus any refrigerant.

#14 sajara

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Posted 25 August 2009 - 06:00 PM

Thanks, all, I really appreciate the input. Based on Scooby's analysis, I will conclude that I'm getting a fair deal.

Too bad my roadtrip will have to be sans A/C since the part won't come in until next week, but hell, it's upper Michigan, so there will probably be plenty of A/C outside. :)

Again, thanks to everyone for walking me through this & shooting me your ideas -- this forum is so very valuable!! :)

--Natalie

#15 Fairtax4me

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Posted 25 August 2009 - 06:53 PM

I'm not real sure what they are talking about when they refer to a "revolution sensor". HOwever, I am looking at the diagram and there DOES appear to be an electrical connection other than just the power for the clutch. It looks like it might be a little inductive pickup to tell the computer if the compressor is running or not. That way, if the compressor were to seize, the computer can turn off the ac so as to minimize other damage. It protects little things...like the belt that runs your water pump. This part is, in fact, called the "revolution sensor". The Subaru Part number is 73190AE000. It retails $120. Labor looks to be about an hour or so. The diagram is a bit unclear as to what all has to come off to get to this thing. So at my shop, you'd be looking at about $200 to change the sensor, plus $78 for evac/recharge plus any refrigerant.


This is good to know. Any way to tell what years had/have this sensor?

#16 Scoobywagon

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Posted 25 August 2009 - 07:21 PM

I'm fairly certain that most cars that came FROM THE FACTORY with AC have that. I say this because I double checked a couple of parts cars. The ones with aftermarket or dealer option air just have the connection for the clutch. The factory units all have this little hall-effect pickup on them. If I had to guess, I'd say there are probably 4-5 different part numbers for variations on year and what type AC you have.

#17 hohieu

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Posted 26 August 2009 - 06:59 AM

Great info., Scoobywagon. However, the wiring diagram for my '99 Forester shows no such switch. I do see an evaporation thermoswitch.

On my 2.5 SOHC, the AC belt in isolated and runs no other accessories. There's another belt that runs the alternator and power steering pump, while the timing belt runs the water pump.

On the H6, does the AC belt also run the water pump?

#18 Scoobywagon

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Posted 26 August 2009 - 09:00 AM

I'm not entirely certain what drives the water pump on the H6 as it has been quite a while since I looked at one. I'm going off the diagrams, here.

So far as your forester goes, if you don't have that little pickup, then you may be the exception. I say this because I've seen the same pickup on XT6's and some Loyales as well as Imprezas and Legacys. I can't come up with a good reason for Subaru to mix and match, as it were, with some cars having that part and others not.

#19 ferret

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Posted 26 August 2009 - 05:24 PM

H6 water pump is Chain Driven.

Foresters didn't have that rotation sensor. They used the Zexel only compressor. ( 98 may be different as it was in many ways )

The Calsonic clutches , IIRC, were the systems that used that sensor. And the clutch plate face has 3 or 4 tabs that stick up to pass by the sensor when the clutch engages. Similiar as most automobile A/C systems are, but one of the differences between them.

Early 90 legacy's I think also used the Zexel compressor as did the SVX.

#20 Fairtax4me

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Posted 26 August 2009 - 05:53 PM

So basically nything with the Zexel compressor will not have it. Mine doesn't have anything there, neither did any of the Legacies I looked at in the junkyards the past couple trips. All in the 94 - 99 range.

#21 nipper

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Posted 26 August 2009 - 07:53 PM

I am not sure about the price but yes. That is the clutch RPM sensor thingy. What it does is check to make sure the AC compressor is spinning when it is on. This is to catch a seizing compressor so it doesnt snap the belt.


I forgot that subarus use these, as its been a while since someone had a problem with one.


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#22 squirrely_1

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Posted 05 March 2012 - 07:52 PM

where can i buy the sensor online for my 2002 h6 3.0 outback sedan ? i have the TSB with this part # 73190AE000 , i want to order it ..But i cannot find it? Is a dealer only item ?

#23 mxmikie

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Posted 06 March 2012 - 08:45 AM

the problem is caused by a bad expansion valve




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