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2004 Forester
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Discussion Starter · #1 · (Edited)
This is the 2nd summer that my 04 Forester (145,000 mi.) has had this AC problem, and the third mechanic look-see, this time at the dealership. Works fine most of the year (use it to dehumidify), until it gets hot - 83 degrees or so. Then it cuts out. The fan still works, but no cool air. Sometimes stopping the car (like at a stop sign) and then starting up again will kick it back on. Occasionally will start up again with no apparent ambient changes. Always suddenly off and on. Every time I've taken it in, they've all noted that it's "slightly low on refrigerant," but either reproduce the problem, when it happens, they can't tell where the problem is. Two have recharged the system but couldn't find leaks. (Also said the amount it was down would affect the temp of the cooled air, but not this problem.) The dealership is speculating on an evaporator temp thermistor, but says they can't test it - that it would be a leap of faith, and $650. They said they checked the electrical system. We're driving through South Dakota in this thing in a couple of weeks - it was miserable last year. Help!
 

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Discussion Starter · #3 ·
Thanks, ferret. My problem is totally related to the ambient air temp. It doesn't cycle off and on frequently (at least doesn't sound or feel like it) when it's running - just doesn't want to work much at all when it's hot. Does this behavior suggest the same problem?
 

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2014 Impreza Ltd CVT
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You can always try swapping the A/C relay in the under hood power box with one of the others there ( like one of the fan relays ).

This would prove if it might be the relay, and if it is, then replace the culprit.
 

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Discussion Starter · #5 ·
Since it's at the dealership now, I may ask them to do this one last, little thing. I printed out the whole intermittent thread (w/pix!), so we'll see!
 

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A common problem on all compressors w/ on-demand clutch is failure of compressor to engage due to wear of clutch plate, causing clutch plate gap to become too large. This gap results in coil magnetic field being too weak to pull the plate in against the spring. You can verify if this is the problem by rapping the clutch plate sharply w/ a stick when AC should be running. If the clutch plate closes and AC works, you've verifed that clutch gap is too large.

Fix is easy also. Remove clutch plate (usually a 10mm head size bolt) and remove a single thin shim from beneath the clutch plate. Measure clutch gap w/ a feeler gauge to verify it is w/i spec, usually 15-25 mils.

PS, your auto shop should know about this issue, so perhaps something else but your symptoms are classic for too large clutch gap. The reason it is heat sensitive is 1) gap may be slightly larger under higher temps and 2) clutch magnetic field will be reduced w/ increased temps.

good luck
 

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Were you able to confirm a solution to this problem? I have the same issue.

My mechanic has checked that the AC is engaging and replaced the relay, but that did not fix the problem. He suspects at this point it is a temperature sensor that's behind the dash. The problem is, it's a significant amount of labor to open up the dash to get at the part and he can't even order a new one ahead of time because the Subaru dealer can't locate the part number for him. So he's reluctant to get into it at this point in case we find out that's not the problem.

Any suggestions?

Thanks
 

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Discussion Starter · #8 ·
Unfortunately Vors, we've been traveling a lot lately, and my regular mechanic is busy as well (added a school bus maintenance contract to his already packed schedule), so I haven't been able to get to it.

I didn't run into anything about a temp sensor behind the dash. When I do get into see my guy, I'm going to have him check into that clutch plate gap issue, but may just go ahead and have him replace the evaporator, which includes a thermistor that that someone mentioned to me on the Car Talk forum. (I'm sure you can find my post there.) Although not cheap, it's fairly straightforward. Like most things, you have to get to it to test it (if testing would reveal anything), so it's a gamble.

This problem is ugly, and obviously a weak link with some Subes. It's starting to get cool here in WI, and my Sube uses the AC to dry the interior air, but it's not working very well (yes, it's starting to malfunction at lower temps too), and my windows are often all fogged up on the inside. Who knows - maybe there are 2 things going on.

Let's stay in touch.
 

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You don't have to be a mechanic to rap the clutch plate sharply w/ a stick. If this causes clutch plate to engage (starts spinning), the clutch gap is too large.

good luck
 

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Well, it's a little too cool now to verify the fix, but my mechanic did find a problem.

I spoke to him about the clutch plate, and he said they had ruled that out by manually triggering the relay, which engaged the A/C just fine. So they knew it was being caused by the computer shutting off the A/C for some reason. Before spending a bunch of time digging into anything too complicated, he wanted to check the freon level, as that was easy. Turned out to be down to 50%, though he couldn't find a leak (seems plausible it lost that much over 5.5 years).

Won't find out for sure if that fixed it unless we have some more hot days so I can see if it happens again, but for now I'm going with that and hoping.
 

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2004 Forester 4EAT
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Anyone thinking of a bad highside safety switch? This happened in my Honda. Compressor would just turn itself off. It was building too much pressure do to a clogged expansion valve. (stupid name, but it's a filter inside the line near the dryer) Check for voltage to compressor clutch while unit is not working.
 

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Discussion Starter · #14 ·
To put my particular problem to bed, I went back to my old (BP station) mechanics, who took everything I told them into consideration, but also thought the compressor looked totally shot - wrapped in rust. They located a used one in like-new condition with a 90 day guarantee for $300, I agreed, they popped it in and it's been working great for more than 2 weeks now. They said that the clutch plate gap was likely a major contributor to the on-off behavior, but the unit needed to be replaced. How the other two entities (including the dealership) that looked at it didn't think the compressor was the problem, I'll never know - it looked like giant, rusty bird's talons were wrapped around it. Although the car's not new, and cause I live in the country, it gets beat up, I think I'm going to blame this on acid rain damage. The car was classified that way when I bought it new (had been on a lot down south, next to chemical spewing smokestacks), and there have been some things that I had to have replaced early on that the same BP guys said looked "older" (drier, warped, corroded), than they should have been. Thanks for all your wisdom! Vors, good luck with yours. Might want to consider the obvious.
 

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Glad to hear it's finally fixed !!!! But I have to agree, Texasforester nailed this back in post #6.

These Zexel compressors use a clutch that is a wear item. As the clutch wears, you see more and more rusty looking dust under the hood. You usually only have 1 shim to remove to adjust this. It also requires a special tool to remove the clutch plate. Nice thing IF you have the tool, you do NOT have to remove the compressor, or open the A/C lines and loose your charge.

I know I will have to do this soon, as when I had my relay problem, I measured my gap at .0022". The spec is .0010"-.0014" when adjusting it. The running check is .0010"-.0020", so I am just beyond that at .0022". But mine would NOT engage when I tried to tap the clutch plate, so I knew it was missing voltage.

Replacement compressor, but more important, finding someone who KNOWS WHAT THEY'RE DOING is better yet.

Thanks for posting back your fix for others to find.
 

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Hi, thanks everyone for this information. I'm experiencing the same thing and am hoping for an easy fix. Replacing the relay I understand as ferret talked about it. However, I'm still new to certain parts of car repair - when you all say to tap the clutch plate to see if it engages.. where in the engine do I hit? :)

I know where the a/c belt is and therefore the compressor, but I'm just not familiar with what the clutch looks like. Then again, I haven't looked yet either, but I thought I'd see if there's someone online who can help me know what I should be looking for.

Thanks!
 

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Clutch plate is at the end of the compressor. When clutch plate is pulled towards compressor by magnetic field and closed, the belt/pulley is engaged and turns the compressor. No clutch plate closure, no cool air. Rapping the plate temporarily jars the plate enough to close. If this happens, see fix in above post by ferret.

If bolt holding clutch plate is readily accessible, you can remove w/ "impact method". Put a ratchet or better a breaker bar w/ 10mm socket on bolt head, and rap the ratchet sharply w/ hammer. Inertia provides enough restrainst to loosen the bolt. Tighten same way, but not too tight.

good luck
 

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Thanks for your response and help! Sorry I haven't been able to get back to this until today.

I tried swapping out the AC Relay and the problem remains so I was going to try and remove that shim from the clutch. I loosened/removed the AC belt and was able to remove the 10mm bolt by creating a jig to hold the clutch plate while I turned the bolt. The jig was just a long strip of heavy gauge metal with 2 machine screws put in it at 1.25" apart. There were 2 holes that this would line up with on the plate so I could hold it still.

The problem now is I'm not sure how to get the clutch plate off the compressor. Does that make sense? Am I in over my head here and should take this to a dealer? I tried a couple flat head screwdrivers to pry it off but I don't want to mess anything up and it seems to be on there pretty good. I heard there was a special tool needed for this, but I thought maybe it was just to hold the plate still like my jig did.

I'd really appreciate any help on if I should keep going (and how to best do that) or just put it back together and not break anything.

Thanks! Also, if someone replies and could tell me this too.. I'm not sure what the shim looks like I'm trying to remove or how to remove it. So the more information the better!

Thanks as always!!
 

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Glad to hear it's finally fixed !!!! But I have to agree, Texasforester nailed this back in post #6.

These Zexel compressors use a clutch that is a wear item. As the clutch wears, you see more and more rusty looking dust under the hood. You usually only have 1 shim to remove to adjust this. It also requires a special tool to remove the clutch plate. Nice thing IF you have the tool, you do NOT have to remove the compressor, or open the A/C lines and loose your charge.

I know I will have to do this soon, as when I had my relay problem, I measured my gap at .0022". The spec is .0010"-.0014" when adjusting it. The running check is .0010"-.0020", so I am just beyond that at .0022". But mine would NOT engage when I tried to tap the clutch plate, so I knew it was missing voltage.

Replacement compressor, but more important, finding someone who KNOWS WHAT THEY'RE DOING is better yet.

Thanks for posting back your fix for others to find.
I think you mean the hub air gap is .010-.014", i.e., 10-14 thousandths of an inch, not 1-1.4 thousandths, correct?
 

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2014 Impreza Ltd CVT
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I think you mean the hub air gap is .010-.014", i.e., 10-14 thousandths of an inch, not 1-1.4 thousandths, correct?
Good Catch ..... and after all this time .... Yes I stand corrected !!!


AND WELCOME to our board .... 1st post ..... sit down and relax..... feel free to hop in anywhere. There are a few of us here for almost 10 yrs ..... others come and go.
 
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