Air Conditioning Kicking Out

[docket]

Here's one for the experts and I think it is probably simple.  The airconditioning works fine in the plane on the ground but does not seem to work very well up in the air.  My guess is that at higher rpm something is going on -- any ideas.

[rbharvey]

I am assuming it is the engine driven compressor and not the early electric system in the Bravo? If so there should be no reason it works better on the ground than in the air. Have you verified outlet temperatures in the air vs the ground or it just your sense that it is worse? Id verify that first

Bob

[carusoam]

Docket,

Rookie advice on this one.....AC is not that popular in the north east.

Consider checking your refrigerant pressure.  Make sure the coils are not blocked.

Most AC units have a controller that is full of safety cut offs to keep the system from damaging itself.  Compressor side temperature may be getting too high (less cooling at altitude) causing the compressor to be cut-off.

These are the most simple typical maintenance things you can do for AC.

As Bob Harvey put it, check the temperature leaving the vents, if it is the same as your OAT gauge, your AC compressor has been turned off.

Best regards,

-a-

[docket]

I know it is very cold on the ground as down here in Houston the OAT over the last week is of the egg cooking variety.  It is the engine driven compressor.  I know that the coils are not blocked and my guess is that we have too much freon in the system and it is causing the compressor to turn off.  I haven't measured it with thermometer but it is pretty clear to tell when it is running and when it is not.  The oddest thing to me is that it works fine on the ground and just seems to shut off indisciminately on climb out and down in the pattern.  I will troubleshoot around on it over the weekend and see if I can find the problem.

[carusoam]

Too much freon would make sense from an over pressure situation.  Acceptable pressure is detected on the ground, but as altitude increases, a higher pressure differential would be detected resulting in a high pressure cut-off.  I am not familiar with having too much freon, but I guess that's possible.  (pressure gauge reading compared to printed range - POH?)

Did you have to to refill it lately?  If it had all leaked out, there could be air in the line causing you some hassle.

Is it possible that it is programmed this way intentionally?  Keep things cold on the ground, followed by cutting it off at an altitude that is supposed to be cold enough to use OAT vents???

That would be nearly smart....  For Houston in the summer, the intentional cut point should probably be 9,000 feet.

-a-

[N9937c]

I fly an R model some and the a/c works great. The owner flies it and gripes about the a/c not working. It turned out he had the fresh air vent in the overhead on full open. The ram air was WAY more than the blower fan could overcome.        Just a thought.

larry

[docket]

Quote: N9937c

I fly an R model some and the a/c works great. The owner flies it and gripes about the a/c not working. It turned out he had the fresh air vent in the overhead on full open. The ram air was WAY more than the blower fan could overcome.        Just a thought.

larry

[docket]

Quote: carusoam

Too much freon would make sense from an over pressure situation.  Acceptable pressure is detected on the ground, but as altitude increases, a higher pressure differential would be detected resulting in a high pressure cut-off.  I am not familiar with having too much freon, but I guess that's possible.  (pressure gauge reading compared to printed range - POH?)

Did you have to to refill it lately?  If it had all leaked out, there could be air in the line causing you some hassle.

Is it possible that it is programmed this way intentionally?  Keep things cold on the ground, followed by cutting it off at an altitude that is supposed to be cold enough to use OAT vents???

That would be nearly smart....  For Houston in the summer, the intentional cut point should probably be 9,000 feet.

-a-

[roundout]

Quote: docket

 Larry, I wish it was that simple but alas it is not my overhead being open. 

[roundout]

Quote: docket

 Larry, I wish it was that simple but alas it is not my overhead being open. 

[docket]

Well, I have been through the system and my bet is that the dryer is failing and moisture is in the freon side of the system.  With a set of manifold gauges on the unit the pressures look rational.  It may also be the fan on the evaporator but I don't want to just throw money bombs at it quite yet by just replacing parts especially when it is still working (just not quite right).  Anyone know a good air conditioning guy in the Houston, Texas area.  Don Maxwell has already taken a swing at this one and he is stumped at the moment.

[docket]

Quote: roundout

 Larry, I wish it was that simple but alas it is not my overhead being open. 

[Mcstealth]

Do you have the specs for each the low side pressure, and the high side? I would start there. If the high side is wrong because of excess refridgerant, that would be easily diagnosed.

[ovation0219]

I am certified in auto ac and have only worked on 2-3 airplane units. but I would suggest you get an ac Guy to conect to the test ports in the tail and run hoses into cabin so you can view them during flight and see what is changing. this will tell you if it is a freon problem or a compressor cutting off, etc.