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 Post subject: AC Repairs
PostPosted: Wed Aug 03, 2011 9:16 pm 
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Joined: Wed Nov 24, 2004 2:25 am
Posts: 18
Location: Central Texas, U.S.A.
In 1300 hours we have lost two AC compressors. The first one the internal parts of the compressor came apart. The second one the high pressure hose going into the compressor blew a hole and thus we loss all the freon, and then of course the compressor froze up and it too came apart. These are about $5000 jobs to clean out the system and replace parts.

Does not seem the high/low limit switch is doing the job it was intended. We replaced it with the new compressor.

Any ideas how we can use our AC and keep our third unit together in one piece?

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 Post subject: Re: AC Repairs
PostPosted: Thu Aug 04, 2011 3:55 am 
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Joined: Fri Oct 29, 2004 3:13 am
Posts: 56
Location: Niagara Falls Area
Can there be something blocking an orofice inside the condenser due to internal deterioration ?
(2 cents only)


 
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 Post subject: Re: AC Repairs
PostPosted: Thu Aug 04, 2011 1:28 pm 
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Joined: Wed Nov 24, 2004 2:25 am
Posts: 18
Location: Central Texas, U.S.A.
We replaced all evaporated valves and pulled all fittings to clean the system. Exactly my thoughts too. We talked about building some sort of filter to protect the compressor, but there is no information on this. We can only hope the new limit switch does its job in case of another failure!

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 Post subject: Re: AC Repairs
PostPosted: Sun Aug 07, 2011 11:12 am 
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Joined: Sat Oct 13, 2007 5:29 am
Posts: 8
I have heard of the limit switches failing before with the high pressure hose blowing of the compressor when the aircraft was parked with the propeller feathered.

My understanding is that the extremely high pressures occur when there is insufficient airflow through the condenser. According, our pilots ensure the air conditioner is switched off when either feather or beta is selected.


 
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 Post subject: Re: AC Repairs
PostPosted: Sun Aug 07, 2011 11:16 am 
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Joined: Sat Oct 13, 2007 5:29 am
Posts: 8
Also, once the systems have been open for an extended period, new filter/driers clog up very quickly. I have heard of engineers evacuating the systems for several hours, fitting an automotive drier, re-gassing, running the system for a while on the ground, then changing the drier to a new aircraft one, then evacuating the system and re-gassing before returning to service.


 
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 Post subject: Re: AC Repairs
PostPosted: Wed Aug 10, 2011 3:44 pm 
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Joined: Wed Nov 24, 2004 2:25 am
Posts: 18
Location: Central Texas, U.S.A.
Good replies. I have wondered about overheating the condenser on the ground with little or no airflow. By the way, both times the system blew we were in high humidity/high temperature conditions in the air.

Having repaired the AC in our plane two times makes me nervous each time I turn on the switch! Cessna should have hired General Motors to put in a system they use in their Suburbans. We have had six Suburbans over the last forty years and only one had AC problems. And my ten year old GM pickup
AC has never had a problem and it still cools like an ice box!

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 Post subject: Re: AC Repairs
PostPosted: Sat Aug 20, 2011 12:50 pm 
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Joined: Fri Oct 29, 2004 3:13 am
Posts: 56
Location: Niagara Falls Area
Thinking of the hot/humid maximum conditions, was the freon topped up anytime prior to it blowing up the first time ?

Like the Suburban example, my F250 AC had longeivity too, but early one season ( at 10-11 years old and 350,000km/220,000mi) I noticed it was weaker on the cold air. The advice then was to add only a small amount, ~ 1 lb of freon, to go easy on the older system / compressor. It chilled reasonable for our humid climate here in Ontario, reliable and adequate, ... forever after. (But our real hot days are few ... where it needs that little bit extra.)

Your AC was working on maximum because (as you have informed) cooling-demand was high. Keeping the freon on the light side (as we could) is likely out of the question. With the extreme heat this summer and that maximum cooling capacity needed in Texas last month, its easy to imagine that anything short of the peak performing air conditioner would be intolerable. Goodluck with it.


 
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 Post subject: Re: AC Repairs
PostPosted: Sun Aug 21, 2011 4:02 pm 
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Joined: Wed Nov 24, 2004 2:25 am
Posts: 18
Location: Central Texas, U.S.A.
PDW, I think the key is a good working high/low limit switch!

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 Post subject: Re: AC Repairs
PostPosted: Tue Aug 23, 2011 5:16 pm 
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Joined: Fri Oct 29, 2004 3:13 am
Posts: 56
Location: Niagara Falls Area
Safety switch malfunction is too bad ... when that scraps the whole system.


 
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