[t3hWIT]

Last week, while driving to NJ to pick up a header, I noticed that I was loosing more power than usual with the A/C on. When I kept the throttle steady, I started to feel the car surging, and the air coming from the vents getting warmer and warmer. I pulled over, popped the hood, and saw the compressor clutch engage... disengage... engage... disengage over and over. I thought that maybe it was due to a loss in refrigerant, so I left the A/C off for the rest of the trip.

I tried it again the next day and it worked properly so I didn't think much of it, but the problem returned later in the week.

On Sunday, I decided checked the pressure in the system, and it was slightly low on the generic gauge I have, cycling between 20 and 35psi. I know there's a small leak at one of the fittings, so I just topped it off and let it go.

Today I noticed a massive loss in power when I turned the A/C on, I had to be around 30-35% throttle to maintain speed, where I'm usually fine with 17-19%. The A/C barely puffed any cool air, and after a minute or so of no power, the CEL light up solid. I did what any self respecting gearhead would do, and I decided to slap it around a bit and romped on the gas pedal. The CEL went away, only to return after a few minutes of normal driving.

I was going to take a video of the compressor acting up and the gauge readings, but the A/C was finally acting normal just idling in the driveway. I did however notice that the low pressure line from the evaporator and the compressor was ice cold and was collecting condensation. I checked the pressure and it's cycling between 25 and 40psi, but again the compressor is acting normal. I haven't had the chance to check the pressure yet while the system is acting up.

I'm coming to the conclusion that the refrigerant isn't boiling completely in the evaporator, the loss of power is because the compressor is trying to compress liquid refrigerant, and the CEL is just a side effect.

What I don't understand is why the refrigerant isn't being held in the evaporator long enough to boil. I was wondering if there is too much refrigerant in the system. The pressure is within the generic range on the gauge, but maybe Subaru's run at lower pressures? Any advice or suggestions?

C/N: Read the last two paragraphs and look at the pictures.

 

[t3hWIT]

The car in question is a 1995 Subaru Impreza. The only modification related to the A/C is an underdriven crank pulley, which is turning the compressor slower.

The most recent work I've done to the A/C system was last fall, when I changed two leaking O-rings. I pulled vacuum on the system, held it, and filled it with refrigerant to the weight listed in AllData.

Two years ago I had the system open for a couple weeks while I was polishing components, and I didn't change the receiver/dryer. I never had a problem with the system before, so I don't think it's related, but I'm not ruling anything out yet.

 

[t3hWIT]

Nobody?

 

[Not-Ewrx]

I'm having some of the same problems. I tryed to top off the system and it did the same thing, kicked on and off, bucked and still isn't running right. I wonder if the system doesn't just need a full recharge. Or the compressor might be shot. Or there is too much water in the system.

 

[MattB]

My car started doing the same thing recently. I can't drive down the highway with the A/C on because I can feel it go on, off, on, off over and over and the power surges making the ride extremely jerky. I haven't seen any CEL's as a side effect yet however. Just my regular misfire and P0420... Lets hope there is an easy fix for this...

OH and just so you know this is happening on a stock AC/pulley system that hasn't been left open for weeks or anything. So it isn't caused by your mods.

 

[Supers587]

My car started doing the same thing recently. I can't drive down the highway with the A/C on because I can feel it go on, off, on, off over and over and the power surges making the ride extremely jerky. I haven't seen any CEL's as a side effect yet however. Just my regular misfire and P0420... Lets hope there is an easy fix for this...

OH and just so you know this is happening on a stock AC/pulley system that hasn't been left open for weeks or anything. So it isn't caused by your mods.

Ditto.

MattB, tell your car to stop copying all my problems...

Maybe they're twins and we don't know?

 

[MattB]

LOL, we really do have ALL the same problems. My O2 sensor came in the other day. I am putting it in this weekend

I need to get rid of my P0420 long enough to get inspected...

 

[Supers587]

LOL, we really do have ALL the same problems. My O2 sensor came in the other day. I am putting it in this weekend

I need to get rid of my P0420 long enough to get inspected...

I completely understand. Try putting in premium fuel for a couple of tanks. That seems to rid my system of the P0420 long enough so I could pass. It's back on now because my header is cracked, but I passed so it doesn't matter :lol:

Sorry t3hwit for the :hijack:

Back on topic!

 

[t3hWIT]

No problem, it's better than no response at all.

I did a bit of searching, and someone posted a pressure similar to mine, but apparently the specs called for 18-28psi. No rpm or ambient air temp specs were listed though, and I can't verify this with any of the PDF service manuals I have. I'm debating just venting some of the pressure and seeing if it helps.

I really think that it's just the pressure too high since it seemed to get worse when I put more refrigerant in it, or maybe I didn't notice it as much before. I can't find the specs though and I'd like to see those before I mess with anything. I really need to get this figured out though, I'm taking a nice long drive to South Carolina next week and would like to be able to use the A/C.

 

[MattB]

I was thinking about it and maybe there is TOO much refridgerant?

It sees it get really cold so it turns the AC compressor off, then it gets warm since its not flowing so it comes back on, then it sees really cold so it goes off...and so on. Possible?

I don't have a clue I am just throwing shit out there...

 

[t3hWIT]

Well I had a class on air conditioning systems, but it's been a year and I'm not digging out my notebook until I move. I was thinking that maybe there was too much in, but again, I'm looking for the pressures first. I know that the system pressure and weight of refrigerant aren't the same thing, but the pressure specs will at least give me an idea of where to start.

 

[MattB]

My friend is an HVAC guy...but not for automotive specific stuff... I will ask him if he has any ideas.

 

[Not-Ewrx]

Well I had a class on air conditioning systems, but it's been a year and I'm not digging out my notebook until I move. I was thinking that maybe there was too much in, but again, I'm looking for the pressures first. I know that the system pressure and weight of refrigerant aren't the same thing, but the pressure specs will at least give me an idea of where to start.

I do think the system has too much pressure in it. I had mine doing the same thing and let some of the pressure out and it got better. It still acts up when it gets really hot.

My friend is an HVAC guy...but not for automotive specific stuff... I will ask him if he has any ideas.

I took thermodynamics last semester and I am tempted to pull my book out and see if I can make figure something out.

 

[t3hWIT]

I'm pretty sure that the CEL and A/C problems are not related. I haven't used the A/C at all today, but the CEL returned randomly, but disappeared when I downshifted and gave it hell. I think that the MAF is dirty. I heard that it's a problem with people using the HKS foam filters, and sure enough, I found dust on the velocity stack when I removed the filter. I'll be cleaning the MAF on Friday when I can get to my tools.

 

[Supers587]

MAF

:lol: :lol: :lol:













That is all.

 

[t3hWIT]

:curse:

 

[Not-Ewrx]

I can't believe no one has any ideas how to fix this. It has to be a common problem.

 

[t3hWIT]

I'm going to purge some of the refrigerant when I get home, I'm thinking that might be the problem.

 

[aresbykes]

did that help with the ac issue? if not, you should drain your whole system and re-fill it....

idk there used to be a place in my town that would do that pretty cheap.


no one likes to kill the environment

 

[t3hWIT]

Just an update, I let quite a bit of refrigerant out of the system, and it's been working good since. It's blowing cold and it went the whole trip from PA to SC without shutting off on me.

The CEL was because of a gummed up oxygen sensor. I just replaced it recently, but it started reading out of range and a new one from Bosch solved the CEL. I got my power back, as well as my gas mileage.

Thanks to everyone for their advice.