Air Conditioner

Im in the Atlanta area and have a flightline AC unit that needs repair. Can anyone advise of an air conditioner guru in the southeast that has experience with flightline Air conditioner units?

What is the problem?

Blows air, but not cold. I'm not a builder and know very little about AC but we've tested for leaks And filled with freon with no change.

I have Flightline's competitor's system ((air-flow systems), and it works great. The science itself isn't any different than it is for automobiles as the components are all the same.

You scare me a bit when you say "filled with freon" because inherent to that "filling" process is measuring the temperature drop as you go. Too much coolant is as bad as too little.

I would search out a mobile A/C repair service. There is nothing that would be foreign to an automotive tech and you just might find the right tech who would be curious and intrigued enough to work on an airplane to get you taken care off. Lots of FBO's could do it as there are several aircraft who have a/c, but they would be expensive and some who worked on early generation systems might tell you to just yank it out.

Good Luck. It's wonderful when it's working.

Have you checked to make sure the compressor engages and is working, the belt is tight, etc....... As a last resort, I would call John @ Flightline and run it by him as well as he would be good resource for troubleshooting your problem. My Flightline (in an RV-10) works great. Best of luck.

Thanks for the replies, I have been in contact with John from flightline and he was great, but it needs a "hands on" inspection. I also like the mobile AC idea if I can't find anyone else.

A couple of years ago my AC wasn't blowing cold. When I charged it, it would work for only a few days. The FBO mechanic was unable to find a leak, even using a sensor. While we were standing at a standstill, a year 20-? year old "kid" walks up and offers to help. Within seconds he says he hears a leak. I guess he did because when we replaced the hose to which he pointed the unit held a charge. Neither the mechanic nor I ever heard the leak. Find a kid.

The last thing I need is another kid!!!!!

tysonr said:

A couple of years ago my AC wasn't blowing cold. When I charged it, it would work for only a few days. The FBO mechanic was unable to find a leak, even using a sensor. While we were standing at a standstill, a year 20-? year old "kid" walks up and offers to help. Within seconds he says he hears a leak. I guess he did because when we replaced the hose to which he pointed the unit held a charge. Neither the mechanic nor I ever heard the leak. Find a kid.

Click to expand...

Or buy some Big Blu leak reactant and spray it on all the joints. Yes it's just "soap", but this stuff works better than any home-brew soap I ever made up.

regards

~Marc

AC

So........... No AC guru's out there? To answer a few questions, the compressor does kick on, we do get air blowing, we replaced the drier, replaced the shreader valves, no known leaks.

Is there a TXV valve in the evap coil? Maybe it needs to be replaced.

~Marc

Have you put gauges on it to check pressure differential between the pressure and suction sides? That will verify you have a charge and the compressor is working. When you replaced the dryer, I assumed you vacuumed the system down before recharging.

AC

There is a expansion valve that has been replaced(if Atis what's meant by a TXV). I have a AC guy helping me troubleshoot tomorrow, will keep you posted

Yes a "thermal expansion valve" is what I am referring to. In your typical cooling system, a TXV controls the amount of refrigerant flowing through the evap coil. I you already replaced it then that's probably not the problem.

regards

-Marc

Hi David,

Automotive/aircraft A/C is pretty simple in theory but it can be a bit tricky to diagnose, but I'll try and give you a quick run down on what you should be looking for -

If the compressor clutch does pull in, but airflow out of the vents is warm, then the first thing I would be doing is confirming correct refrigerant charge by connecting the gauge set. If the readings are low on both red and blue (hi and low pressure) gauges, then you're looking at a low refrigerant charge (possible leak), TX valve sticking open, or a tired compressor.

Checking for pipe temperatures at the inlet and outlet of the evaporator will help diagnosis here, both pipes should be cold to the touch, if the inlet (From the TX) is cold but the outlet (to the compressor) is warm, then you're probably looking at a low refrigerant charge or a lazy compressor, if both pipes are warm but the correct charge is present in the system then it is more likely to be the TX sticking open.

If you do open the system to atmosphere for repairs, which it sounds like you've done already, then you need to place it in a vacuum (using an A/C evac pump) for at least 20 minutes to rid the system of moisture - if there is any air or moisture present when you add fresh gas, it will cause the gauge set to do some weird stuff - and can harm the system long term. It is also prudent to replace the drier at the same time.

The best way to correctly charge the system after repair is by weighing the refrigerant as it goes in, making sure it gets the recommended system weight, but it can be charged correctly by an experienced person monitoring pipe temps and gauge pressures. Too many people just throw the gas in and hope for the best!

This is only a basic overview, and there are a few other less likely reasons for your A/C to not function correctly, but I could go on about it all day!

Feel free to list your observed pressures/temperatures here and I'll do my best to help!

Cheers

Hugh

Ac

Thanks everyone! I'm troubleshooting today and will keep you posted.

AC

Ok, I finally did some troubleshooting and found many leaks (the installer must have not liked the idea of O rings). As recommended I started out with about 16 OZ freon and the compressor kicked in, but only for a short while. Now the compressor does not kick in at all. The fuse is not blown, the dryer was replaced, there are no leaks (the system holds a vacuum for more than 24 hours). Any ideas???

There may be a built-in "switch" that locks the compressor out if the charge is low. check for voltage at the clutch. You should be able to energize the clutch and observe it working without the engine running.

~Marc

there is, or should be a high pressure and low pressure switches on the refrigerant lines or on the compressor that go to the relay that energizes the compressor clutch coil, no need to be running, check power at compressor clutch coil, then back to relay, then back to cut out and cut in pressure switches, these can be wired making power or ground for the coil in the relay, then back to panel switch and then fuse. you need at least 50ish psi in the system to close the low pressure switch, the high pressure switch usually opens around 300. a note about air, if any is present in the system, this is a non condensable gas and will cause both hi and low pressures to be higher and you will have less cooling, as mentioned above, a vacuum needs to be pulled any time a line is exposed to air.

I hope you can finally get it working right, Dave.