A/C Fluctuates Between Warm and Cold

Hey, I just recently bought a 2005 Legacy GT with auto climate control and ive noticed that when I'm just driving around with the a/c on it will fluctuate every 10 or 15 seconds to a little warmer temperature and then get colder again and continue doing this. Then at a stop it will get warmer again. I've tried it on auto and just on the manual control and it still does it.

This is the normal poor performance of the AC in all Legacies.

this is the normal poor performance of the ac in all legacies.

 

+1

It cycles the AC compressor on and off, and you can feel the difference. Otherwise it seems to work alright in my experience.

My Legacy does not fluctuate between warm and cold. I hate AC, I'm an windows open man, but when I have AC on it stays cold the entire time. The only time it gets warm is when you floor it, triggering the AC compressor to shut off. I have found the HVAC system in this car to be rather awful though. I NEVER use the "auto" mode.

Set a full cold 65, manual mode, it will still cycle the compressor at a very frequent rate. If you aren't set on recirc it's even more annoying -- especially here when you're blasted by hot, humid outside air for 5-6 seconds out of every 30.

 

Other cars cycle the compressor but it's almost unnoticeable inside the car. I don't know why it's so obvious when the Legacy does it.

Set a full cold 65, manual mode, it will still cycle the compressor at a very frequent rate. If you aren't set on recirc it's even more annoying -- especially here when you're blasted by hot, humid outside air for 5-6 seconds out of every 30.

 

Other cars cycle the compressor but it's almost unnoticeable inside the car. I don't know why it's so obvious when the Legacy does it.

I also don't get why it's not obvious to me in my Legacy .

 

I'll have to turn the A/C on when I get in later and see. It's been super humid and in the mid 90s these past few days, so I have been using the A/C a little bit and still haven't noticed it doing this.

So I had an appointment with the dealer to check it out but they won't be able to do anything then I guess. Thanks for the responses

if it's really bad, it could be the low pressure switch, or try pumping some more freon in there

The cycling when its on is partially annoying... the airflow whens it off is even more so to me, I've tried turning it off with different settings etc but there always seems to be substantial airflow from the last used vent.

Press the recirc button after turning it off to prevent air from being forced through the vents.

My car does not fluctuate cold air temp.

Yeah my '06 doesn't fluctuate either. Maybe it needs some refrigerant? Maybe you pissed off your car?

I've experienced the same rapid cycling issue in my '08. As stated above, using recirculate helps a lot.

one reason why the air will get warm is due to the AC clutch. When the engine speed is increasing, the compressor disengages to free up power, and this also protects the compressor from high rev damage. And at contsant engine speed the compressor will engage and disengage periodically for fuel saving.

I think that Subaru was overzealous in their cycling of the AC compressor. They made it cycle way too often and disengage too easily. All of my previous cars, including several with 4-cyl motors NEVER did this obvious AC cycling and would get the cabin ice cold in just a few minutes. This should be fixable with a simple software update to the ECU.

I'm going to let them do a recharge on it to see if that helps at all. But the strange part is it gets worse when I'm at a stop vs driving down the road.

...the strange part is it gets worse when I'm at a stop vs driving down the road.

 

Same here.

 

Let us know if the recharge makes any difference.

 

Thanks.

I think the "off time" increases while stopped, and also perhaps the fans don't move enough air across the condenser to keep the air cold.

 

The very first Eclipse (1990) cycled the compressor when in "economy" mode (it also had an always-on mode) and you never felt temp fluctuations like in the Legacy. You'd think AC technology that was 15 years newer would be an improvement.

All modern cars are required to have fresh airflow into the cabin even when the HVAC system is turned off.

So in the summer, when the HVAC is off, you're always going to have nice warm engine air coming through whatever venting you have it set on.

Nice in the winter, not so much in the summer.

And to flog a horse that if not dead is at this point in mortal danger of expiring, the hot AC air cycling is normal

 

 

Sure... but my other 2 vehicles, and other vehicles in my household are no where near as bad.

Well, they were most likely engineered and manufactured in very different ways.........

And it still happens in the other cars you own/have driven so..........

Not sure what you're getting at

 

That other vehicles have airflow, but passengers do not ask all the time if I accidentally have the heat turned on. There is a difference between the cabin not being "sealed" and it feeling like the fan is still running.

I'm going to let them do a recharge on it to see if that helps at all. But the strange part is it gets worse when I'm at a stop vs driving down the road.

 

 

I have an '08 that's going in on Wed for the same thing. I've never had a complaint with the AC until about 2 weeks ago. As others have mentioned, I get 5 or so seconds of warm air followed by cold air. It's rather annoying on hot days.

 

According to my thermometer, the air coming out of the vents is between 55 and 60 degrees with it set on 65 and recirc. I never use the auto setting as I think it's worthless. The dealer says that it should be colder than that so they're going to check it.

 

I will post their findings as well..