I put a can of Freon in the Saratoga's AC yesterday and it made a big difference. I have only owned the plane for a month now and the previous owners said they would have to put a can in about half way through summer. It has to be leaking somewhere, how do I find it?

Hi Mike,

Most GA A/C systems are stone simple, but require a certain amount of fussing to chase down leaks due to the way the systems are plumbed.

If I recall the Piper system, you've got an engine compressor and those lines run to the back to the evaporator & condenser in the back. That's a lot of tubing to chase.

The standard way to chase leaks is to evacuate the system, and set it up to hold a vacuum and watch it for 24/48 hours. Finding none, you when want to pressurize the system with N2 for the same period. Sometimes it will hold a vacuum, but not pressure.

If you see a leak down anywhere, time to get the soapy water and chase them. Unless you get lucky, that probably means pulling the interior. No one I've talked with thinks that UV leak testing is worth it, but that's also an option. Pay special attention to elbows and flex lines.

Hope this helps.

Best,
Rich

The electronic leak detectors work well

look for wetness....oil will be escaping with the Freon and leaving residue.

Sounds like I maybe happy just putting 2 cans in it a year!

No, my avionics guy use to do heat and air so he has all the gauges and sniffer. Maybe we can find the leak fairly easy. When the system is gassed up it works very well. I do loose some speed when the condenser door opens though.

before you put any more gas in it....charge it with 400 psi of nitrogen....and spray all the fittings with soapy water....and look for bubbles.

Evacuate the system and fill with nitrogen, 150 PSI. Spray soapy water around fittings and look for bubbles. They are very slow filling bubbles. Look in the easy places first such as around the compressor fittings, fittings to evaporator, evaporator itself, fittings to receiver/dryer, and condenser and its fittings.

Also look around the front seal on the compressor, they can leak. Also the seam on the compressor where the backplate fits on (not all compressors are designed like this) can leak.

Any pressure switches can leak and should be sprayed to look for bubbles.

UV is often a waste of time and sniffers often beep at everything especially with small leaks.

Do not use anything that says it will seal the leak, that will just clog everything and make a mess.

All above comments good, also a black light can also help find leaks as the oil in the system will leak out with gas and can sometimes be seen with black light. Compressor seals are common leak areas and on all PA 28/32/34/44 series aircraft one of the more challenging areas to check are the lines running from compressor to rear of aircraft to condenser and evaporator. These lines are routed from the firewall into the keel beams along the belly of the aircraft, virtually no access to these, capping and pressure checking is one method of checking this area. Piper did not use the best hose for this installation.

I have done various air conditioning hoses

Flare to Flare
Flare to male oring adapter
37 flare to 45 flare

Today I received a set from early baron

Previous shop had a 37 flare and the compressor was 45 flare .

This is why he has seepage

There is a difference......

GB

I assume the system is R12. The best way to find a leak is to evacuate the system, pull a vacuum, add florescent dye for auto ac systems and recharge with the proper amount.
Run the system as you normally would and when it stops cooling as it should, use the pair of yellow glasses and a black ultra violet light to see the dye stains were it came out.
The stains will be a brownish color easy to see. You should be able to buy a kit with all needed
parts to do this at a car parts store. If not, call your car repair guy. He should be able to help.

I wouldn't keep adding R12 (assuming it's R12). If there's a leak it'll continue to leak and refrigerant is expensive. My experience has been fixing aircraft AC is not a quick process, but it's not hard. Like most things cutting corners or thinking it is good enough will lead to disappointment.

I don't recommend using dye after the interior of friend's P-Baron's interior was stained from that stuff leaking/spraying. Once it got everywhere it became hard to find leaks. 50/50 mix of dawn dish soap and water just works.

Having fixed my PA-46 Malibu's system, start with Nitrogen. Take it up to about 200psi with a very good set of gauges. Now take 50/50 mix of water and dawn dish soap and soak every fitting using a spray bottle or brush it on. Even the smallest leaks will be very easy to see. My final leak was about 5psi per day and it was still easy to find.

Fix the leak and repeat.

Once you get the system to hold 200psi of N2 for a week you've solved your problem. Make sure you take note of the ambient temperature when you start the week as PV=nRT still applies and the final pressure needs to be adjusted for any temperature changes in your hangar.

I forgot if it was Beechtalk or elsewhere, but MidState Aerospace were able to make DOT approved aviation flared A/C hoses for me. http://midstateaero.com/ On someone's recommendation I did use Del Fitting seals for the flared connections. Also the "rubber" seals do wear out on the schrader valves and around the pressure switches over time, if you do need to replace them make sure they are compatible with your refrigerant and oil.

While it's apart with the nitrogen verify your hi/lo pressure switches are set correctly and working. Before you charge it, you should install a new dehydrator, pull a vacuum and charge per the maintenance manual. Make sure the right type and amount of oil is in the system.

While I was doing this, I did befriend a local hose shop to look at my hoses. While he refused to make aircraft hoses he noticed one of my female ends wasn't sealing correctly and it turns out a semi-hidden male fitting at the forward pressure bulkhead was deformed.

I did this all about 4yrs ago and nothing like having cold A/C at the flip of a switch (used it yesterday).

Unless you get lucky, that probably means pulling the interior.


Best,
Rich[/quote]


One of the few nice things about the Piper is the Freon lines run through the HAT channels on the belly so you won't need to pull any interior.

I find alot of the leaks on the Pipers can be traced to bad service port core o-rings

One of the few nice things about the Piper is the Freon lines run through the HAT channels on the belly so you won't need to pull any interior.

I find alot of the leaks on the Pipers can be traced to bad service port core o-rings[/quote]

Hi Bill,

Interesting.

My only other comment would be to repeat what I said above. Don't assume new flexible hoses work. We went through 3 sets of flex hoses to the condenser before we found a set that didn't leak like a old garden hose.

Best,
Rich

The one's from mid-state where much better built the the old Piper hoses I took off the plane. I'd have to check but IIRC mid-state pressure checked their hoses. Unfortunately or fortunately all my hoses were built to order using the old hose tags (i.e. wait or pay to be put at the front of the line).