AC question/problem.
 

Hello all, just almost baked myself due to schizofrenic behavior of my Climate control. It works perfectly in common summer temepratures - within 30 C. As this summer is very hot here, I am using it very extensively now. What happend to me was at 34 C it started to behave very strange. After starting engine, cold air blows for a while, than seems AC is switched off and I can get very hot air in. After while it goes cold again and than hot... It seems it works better in high revs but can not tell it for sure. Anyway run AC diagnostic and no error code. AC compressor works all the time so this is not weak point, cooling medium is there and as for diagnostic all sensors send correct data. As I wrote at the beggining it occurs only during very hot days.
Any idea?
I will try to change AC unit from my spare care to check but have strane feeling that it is working OK.
Can be caused by low presure of cooling media? What is right presure?
Petr

Sounds like everything is working the way it should (no codes, compressor engaged). I would inspect the A/C condenser to ensure it is clean. People have had them plug up with dirt, leaves, etc and cannot adequately cool the R12/R134. This would happen in stop and go traffic but is not an issue at highway speeds.

Petr

If you are having trouble with this you really ought to go to an Aircon specialist to get it checked.

Partly I say this because I know sweet fa about aircon. The other part is because in swopping components etc, you should recover the refrigerant for green reasons. For safety reasons also, if yours is R12, and it vents against a hot pipe, it could release phosgene gas, which is very dangerous.

There are two pressures while the system is working, the high pressure side and the low pressure side. I don't know what are the correct levels. Low should be about 20 psi I think, and the high pressure maybe 280 psi. the experts will know. There is a device called the trinary switch which sets three different pressure levels, depending on which mode is working.

If you are sure your compressor is working, then I suspect you may not have enough refrigerant in the system. Get it topped up at a specialist.

The other fault you could have is the possibility of dirt or contaminant in the system, that could be blocking valves on you. This can even include water, which if in the system could freeze up when the system is working hard, and block valves. Until the ice melts, you would be getting hot air.

These are just suggestions. maybe someone with better aircon knowledge will chirp in. Best advice, get the pressures checked with an AC specialist.

Joe

I let it clean and refill it as I did my engine work year and half before. It was done by local Subaru dealer who owes Toyota dealership and service with AC shop as well. Maybe try to check it with someone else. Definitely it is working in normal temps, it means compressor is working and system is cooling. It just occure as it seems it is overheated so no dirt or such a problem. If there is dirt or watter it would behave the same all the time, not only "overheated", does not it?
What I suppose there is problem with presure, ec not enough refrigerant, so if there is normal temperature is easy for system to cool but if there is extensive temperature and systems wants to use maximum power it can not deliver it as presure is too low. Is my logic OK?
Thanx Petr

Sure is OK. That is how I see the problem also.

The AC system is fairly complex, so it is also possible you have a valve that is sticking or blocking intermittently. Also you could have a bad relay that could be closing when the system is working hard, but is not seen as a problem when the diagnostic runs.

If you have a small leak, they put in dyes and see where the leak is coming from. Most likely your problem is low volume of refrigerant in the system which is causing lack of pressure, and so failure to cool in hot conditions..

Joe

Yep they had refilling it problems with leakage and have to fill it several times as couple of o rings went out, now it seems it is ok as I can see bubble there and it is cooling. I will go to another AC shop for test.
Thanx, Petr

gas gas gas
 

I would say I know less about this subject than Joe, (no offence old friend), but I would agree with Joe on the most likely problem been short of volume of gas. This seemed to be my problem a couple of years ago. It is still on R12 gas, the garage I took it to reclaimed the gas in the system, measured it (it was about 25%) and refilled with the correct amount. The system has a safety cut out so it won't run dry but if not the correct amount it will most likely run hot and cold........so I've been told.......saying all that an AC specialist would still be your best.

John from Scotland

NB A strange tlhing happened to mine with the heat.....it curled the blades on the near side fan that much it fouled the rad!...had to straighten them with a hot air gun.....and people think crop circles are weired!

Joe, any photo's of this years JAE.....I was well P****d I had to miss it...

I had a similar a/c problem on a V6 Honda, it was caused by the evaporator freezing solid with ice caused by unusually high humidity, this cut off the airflow. After about 30minutes it thawed out and the airflow resumed until it froze again. At one point I had snow blowing out of the air vents. Try using it at a setting above the coldest, say 20c.

Arthur