Air Conditioning Cutting In/Out 1995 Impreza

[myellin]

Toward the end of last Summer my 1995 Impreza Wagon with 180,000 miles starting having strange problems with the Air Conditioning.

 

1. When I turn the A/C on, sometimes it will work great and blow nice very cold air. But sometimes when I turn it on, it just blows air that is hotter than the outside air, and the air is not dehumidified.

 

2. If the A/C does blow cold air when I turn it on, it doesn't last. After a random amount of time ranging between 30 seconds and 15 minutes, it will switch over gradually (over about 20 seconds) to blowing air that is hotter than the outside air and not dehumidified.

 

3. If I let the A/C blow the hot, not dehumidified air, after a random amount of time (anywhere from 5 minutes to never), it may start blowing cold air again (or not).

 

4. If I turn off the A/C when it is blowing hot, not dehumidified air, wait some amount of time (1 Min, 5 min, whatever) then turn it on again, I'm back at square one. It may work, or it may not.

 

I've asked the dealer to check and fix this problem during three separate visits (for other routine maintenance), and each time they have told me that not only can they not find the problem, they have not been able to reproduce it. So I go out to the parking lot, jump in my car, and get a few miles down the road and... hot air. My dealer's maintenance dept has been great in every other area, and they have told me that they have run it for long periods of time in the shop, and I believe that they have tried.

 

So I conveniently forgot about this problem during the Winter, but now it is Summer again. I was going to try to tough it out rather than replace the car, but I've just gone through my first stop/go traffic jam in 85 degree weather. It wasn't much fun with only the windows and the hot air vent. Since the dealer hasn't been able to fix it, I don't see any hope in taking it elsewhere, and also since the car has 180,000 miles on it, I certainly don't want to sink a lot of money into it.

 

More notes of interest. I'm the original owner. I think they added A/C coolant once over those 10 years. If I turn the temperature knob to "hot" I get Heater air right away. If I then turn it back to cold, it doesn't give me cold air (unless it had already been blowing cold air). It doesn't matter what position I have the vents in (i.e. A/C, Max A/C, DEF, etc..). They all have the same problem. If I have the defogger blowing when this changeover happens, it really does a number on my windows. Since the air goes from being cold and dehumidified to being hot and humid, my windows fog up within seconds. I usually have to switch it over heater to clear it, or grab a towel... anyway, you get the picture.

 

Does anyone have any ideas? I'm not a car mechanic, but what occurs to me is a loose wire, flakey switch, or bad sensor? Since it blows really nice cold air sometimes, I don't suspect low coolant, but my neigbor says that if it is borderline it could be fooling a sensor into shutting the system down automatically?

 

Thank you in advance for any ideas,

 

Myellin

[Cougar]

I would suspect the air blend door is changing and causing this to happen. The door motor is controlled by a vacuum from the engine. There may be a small leak in the system that is causing this to happen. When the door is in the wrong position it will let the heater air in.

[Tiny Clark]

Ditto on what cougar said, must be the flapper. A lot of newer cars don't use a valve to close off the hot water going to the heating core, they just divert the air inside the ducting.

[Setright]

The valve in the cabin heater is extremely old-tech. Many manufacturers abandoned this when cars were given fixed roofs.

 

If the flap door is to blame, the air would be hot, but still DRY.

 

Your coolant level may be fine, what I would worry about is you refrigerant level. Has the system had the wrong type of gas added? Mixing them can cause them to thicken and loose effect.

 

The cooling element in the cabin should have a temp sensor on it. If this is too close to the element it may overeact and tell the compressor to shut off. The idea with this sensor is to avoid freezing the element, but if the sensor is loose it may occasionally come into contact with the element.

In fact, I would check up on this temp sensor first. Access shouldn't be too tricky from below the dashboard on the passenger side.

[Cougar]

If the flap door is to blame, the air would be hot, but still DRY.

 

Setright,

 

The way I understand the operation of the door is it selects either the heated outside air or, the air conditioned, dehumidified air. The air flowing through the heater section doesn't get dried, if I understand the system correctly. It just flows through the heater core and into the cabin. When the AC mode is selected this area is normally shut off by the door and air from the AC section is allowed to flow.

 

We may be talking about two different doors due to the differences in our idea of what is the cause of the problem.

[avk]

The ventilation controls on a '95 Impreza are cable operated, except the recirculation actuator which is electric and of course the compressor switch. If there's enough refrigerant in the system, I would suspect a faulty switch in the control panel, the one operated by the dial, that should be closed in "AC" and "MAX AC" positions.

[myellin]

This weekend my neighbor took a look at my Impreza with me (he does some home auto work). He put a pressure gauge on the refrigerant line, and said that looked fine. We ran the A/C for about 15 minutes with the car sitting in his driveway and it ran OK the entire time (which is what the dealer was experiencing). We didn't have time for me to drive around to get it to fail, so he showed me where the compressor clutch is, and he told me that the next time it acts up, to pull over and take a look to see if the compressor clutch is engaging at all. He also showed me the refrigerant pipe? He said I could feel that metal feed pipe to see if it is cold.

 

I'll check these things out to get some additional data points and keep you all in the loop. Your comments have been helpful and appreciated.

 

Thank you,

 

Myellin

[rcoaster]

Hmmm.. It could be a relay going bad causing the compressor to cut out. Another thing to check is the pressure switch. That could be going bad, thinking that there's no freon in the system and causing the A/C to cut out to prevent damage to the system.

[Setright]

Cougar, the air is routed through the air-con heat exchanger, then the cabin heater. Unless the door routes it past the cabin heater. Meaning that if the door is in "heat" position, the air will be drawn in, cooled and dried and then heated.

 

Only if the air-con heat exchanger is not cold will the condensation evapourate again and hot wet air will enter the cabin.

[Cougar]

Thanks for the clairification Setright. So does this mean that the AC comes on whenever the heater is used? I have heard that the AC is used for the defrost mode but not the heater mode.

[Setright]

Not in my car, but yes, in some models the aircon comes on along with the defrost setting.

[myellin]

I've been driving around for the past two days with the A/C on as much as I can stand it (the weather here has been under 60 degrees F for the past two days). I had some long trips (over 1 hour) and It hasn't failed again yet. It has been producing consistently cold air. My neighbor says there is nothing he poked or prodded during his investigation under the hood that would have magically 'fixed' it, so now I'm wondering if the outside temperature also somehow has something to do with the problem.

 

He also suspected a vacuum leak, and he asked me to see if there is any link between acceleration and the failure (he said the vacuum differs depending on the demands on the engine). It has failed in the past on the highway as well as in stop/go traffic situation, so I don't think that is a link, but I'm watching that closely regardless.

 

The rest of this week is supposed to be cool, but I'll keep running the A/C as much as possible. When it eventually fails again, as it will, I'll be ready to jump out and check the compressor clutch and refrigerant line temperature.

 

The funny thing is that on the really hot days, when I really need it, it runs on its own schedule, while now, on cooler days, it's cranking out consistently frigid air. I guess that makes sense that I wouldn't notice that before, since I don't normally run the A/C when it is cold outside - I would normally just use vent or a hint of heater.

 

Thank you,

 

Myellin

[Setright]

If the now working AC is too cold, just dial in some cabin heat. No need to freeze yourself.

[myellin]

Here's some additional Information:

 

The A/C failed again on a day this week that was slightly warmer, so I stopped the car, kept the engine running and the A/C going (blowing non-cool air) and popped the hood.

 

1. I watched the compressor clutch for several minutes, but it did not turn at all even though the A/C was on full.

 

2. I felt the refrigerant line, but it was not cold.

 

Note: When the A/C has been working, the compressor clutch spins periodically, and that refrigerant line is cold. Thanks to my neighbor for having me check those two items in a working and nonworking situation.

 

I'm hoping this helps narrow down the possibilities a bit more.

 

Any thoughts are definitely appreciated.

 

Thank you,

 

MYellin

[Setright]

Maybe the AC clutch is worn. Is there a lot of red dust around the AC compressor?

 

OR, the compressor is not being told to switch on. Meaning a loose connection or a faulty sensor. Please have a look at the heat exchanger inside the cabin vent system.

[Cougar]

I would check for power getting to the clutch. If there isn't any then I would suspect the relay as the problem. The symptoms you describe make it sound like a faulty relay, though it could be other things, but that is the best bet in my book.

[myellin]

After some testing, it looks like the problem is the compressor clutch.

 

We put a circuit tester on the clutch, and saw that voltage was being sent to the clutch, but it wasn't moving. We then gave the clutch a slight helping 'whack' in the right direction, and it started turning.

 

The visible part of the clutch is very orange in answer to an earlier question. I don't see 'dust' separate from the unit, but the surface of the clutch is very orange.

 

Interestingly, when we had the compressor turning (and the A/C) going, then I turned off the ignition, the compressor clutch started jerking erratically backwards for several seconds. My neighbor thought that might be due to pressure within the compressor and could be perfectly normal. Anyhow, it looked unusual so I thought I'd share.

 

To fix this, does it mean replacing the compressor and the clutch, or just the clutch? My neighbor thought they looked like one unit. This looks way beyond my capabilities, unfortunately. I'm going to give my local repair shop a call to see what it would cost to repair. I was kind of hoping in the back of my mind that it was just going to be a loose connection somewhere... oh well. :-(

[avk]

It might be a matter of re-adjusting the gap in the clutch. If it became too wide, the electromagnet can't pull it in against the return spring. Special tool may still be needed for this job.

[myellin]

I talked to my dealer and he said they would approach it by replacing the AC compressor. He said that part is about $575, plus about two hours of labor. That's too pricey considering the age of the car (1995) and the mileage (185,000). If I have the car in for other servicing (i.e. oil changes) I'll ask them to take a look at the spacing/gap (thanks for the suggestion).

 

I may look around to see if anyone sells a refurbished or less expensive part (suggestions would be welcome), but at this point I think my Subaru is about to become my official Winter driving car, and I'll look for something newer for my primary car (the heater still works great even if the AC doesn't).

 

Thanks to everyone for all your help in figuring out the AC problem!