A/C problems and questions

[theterrells]

71 23' Land Yacht with Coleman A/C

The fan and compressor runs,but unit not cooling.

When unit is off pressure is 150lbs and when turned on the pressure slowly (5-10 seconds) drops to zero. Unit cools for the 5-10 seconds as pressure drops. Then just blows warm air as compressor continues to run.

Reference the attached picture:
Tube "A" frosts up from "B" to the evaporator cover
Tube "C" cools slightly
Pressure taken at valve "D"

Any help or suggestions will be appreciated.

Floyd Terrell
Saraland, AL

[Phoenix]

Symptoms and pressures sound like the system is low on Freon (or whatever coolant is used). If the refrigerant is low, you probably have a leak. So, repair will involve leak troubleshooting, leak repair, evacuation and leak testing, and refilling -- all of which requires special equipment.

Unless you have the proper manifold gauge set, are familiar with cooling system safety requirements and have done this before, this is probably a job for the professionals. Alternately, someone you know may work in the appliance industry and can help or do this for you. (RV units are more like your refrigerator/freezer than your auto air conditioner, especially regarding the refrigerants and gauges used.)

[perryg114]

It looks like it has a clamp on shrader valve and they are prone to leaking. I suspect it is low on Freon, like Phoenix said. Get a schrader valve sweated onto the low side and then look for leaks. You maybe talking more than it is worth before it is all over with. I gave up on mine and all it needed was some new caps and a fan motor.

perry

[GeocamperAS]

I agree with the leak. If you did not put on the "D" clamp on valve, that means it has been serviced before. Unlike an automobile A/C you can not just top off the freon. In this case the leek needs to be found and repaired before the unit will hold the freon. If the leek is in the evaporator or condenser coil, it can not be soldered. The coil would need to be replaced.

[Phoenix]

Note: Regarding your pressure measurements, there should be a plate or label that indicates the proper low and high pressures, and the refrigerant and amount used in the system. The high pressure sounds OK, but you measured this with the system turned OFF. You need to measure these with the system ON, and they should match the specifications on the label. Typical values might be (and these may be incorrect for your system), low side = 30-40 psi and high side = 120-160 psi

[HowieE]

If you have 150 lbs while the unit is off it is LOW on charge but NOT EMPTY. There is enough gas in the unit to look for the leak. First test is to look for an oil spot as oil is pushed out with most leaks or put AC leak detection soap on that clamp on valve and look for bubbles. If visual doe not give the answer a flame or electronic leak tested might work.

Test that vale before you toss it.

[GeocamperAS]

Originally Posted by HowieE

If you have 150 lbs while the unit is off it is LOW on charge but NOT EMPTY. There is enough gas in the unit to look for the leak. First test is to look for an oil spot as oil is pushed out with most leaks or put AC leak detection soap on that clamp on valve and look for bubbles. If visual doe not give the answer a flame or electronic leak tested might work.

Test that vale before you toss it.

Sorry Howie, but I would not use a flame for leak detection. Although it is a common practice, (when the flame turns green you found the leak) it is no longer recommended. Even though freon in non-flammable it will still burn. When the burning happens your blue flame will turn green. This burning of the CFC's produces a highly toxic gas called "Phosene Gas" and should not be inhailed.

[HowieE]

You are correct in everything you say about a flame leak detector but that may be the only option to some of us that have not advanced into the 21st century.

[perryg114]

I would check for gross leaks with soap before the flame detector for the reasons tiger mentioned above. I suspect you have a leak around the clamp on schrader valve and maybe some other place as well.

Perry