Freon (134A) leak

[Woody]

After spending many $ at both Liberty and Prevost Jax analyzing the OTR air system we charged it with 20# 48 hours ago and today when checking to ad an additional 5# per Prevost --- it was all gone.

We spent a lot at Jax and they couldn't find a leak although it wouldn't hold a nitrogen charge.

We had our bus company in Maine search and then charge the system with 20# - this held for 3 months.

WHO IS THE BEST COMPANY TO FIX IT FOR GOOD??

Thank God for global cooling.

All advice will be appreciated.

[Jon Wehrenberg]

Woody,

The answer you may not want to hear is Prevost. Nobody knows the routing of lines or the location of fittings and components on the OTR system better than they do.

Having said that, to lose that much Freon in such a short period of time is a substantial leak. Using the bubble solution or a leak detector that size leak should be readily apparent.

In our OTR systems, I suspect most leaks are going to be the seal on the compressor behind the clutch. If that is the leak you will not need bubbles or a leak detector because it will be an oily mess. The fix is less than $100 for the parts related to the seal repalcement, and a couple of hours of labor. If that is the source of the leak I would take the coach to a Carrier dealer. Anyone who works on large commercial AC units or the refrigeration units on trailers will have the expertise.

[johnklopp]

It sounds like you are getting the run around by part time refrigeration technicians. Any qualified technician should be able to locate and repair a leak of less than 1.0 ounce per year. I would consider anyone working on busses as marginally qualified compared to a Carrier or other full time refrigeration air conditioning mechanic as suggested by Jon.

The probability of having a leak in a concealed line run in the coach is typically slight although possible. There are dye solutions than can be added to the refrigerant oil that circulates with the refrigerant through the entire system. The dye will show up under an ultraviolet light and is typically used on very large systems with runs measured in hundreds of feet. Our busses are actually small systems when compared to one in a small commercial building or a large house.

Leaks will typically occur at seals or joints. If you are adding 20 Lbs. or refrigerant and looking for the leak with bubbles you are wasting money and it’s actually illegal subject to a substantial fine for the technician doing the work. A technician should have an electronic sniffer detector capable of finding leaks as small as 1/10 of an ounce a year. The system should be tested with a pound or so of refrigerant and then pressurized with dry nitrogen to several hundred pounds of pressure. If they are actually using soap bubbles, find another technician.

If the leak is indeed in an inaccessible location, the technician will begin to isolate components and piping runs in much the same way you would look for an air leak in your air suspension.

After you select a local refrigeration air conditioning technician to locate the leak, require him to prove the leak has been eliminated by pulling a vacuum on the system to at least 500 microns or lower. If his vacuum pump won’t pull the system down that low, it’s still leaking. Close the valves on his charging manifold and verify on his digital vacuumed gauge that the vacuum pump is capable of going below 100 microns without your system connected.

[Jon Wehrenberg]

Woody seemed to suggest that Prevost couldn't find the leak in a system charged with nitrogen. Admttedly 134 will escape where R12 may not, but a loss of 20# in 48 hours is a leak so large you should be able to see the refrigerant oil around where it is leaking.

Ditto on the vacuum, and I question why they couldn't find a leak that large. If not the only leak I'll stick with my guess that some of not all is at the compressor seal.

[ToyMan]

Woody, I think your system was originally R-12. Have the hoses been changed to support R-134A? R-134A will leak in a system designed for R-12.

I had a compressor seal replaced at Coach Worx on my R-12 system. No leaks at all.

[AmeriStar]

John is exactly right. A properly trained automotive ac tech will take the steps that John described to determine your 'leak'. It is seldom that a small repair shop will have this level of technician on staff. Don't be afraid to ask the shop you choose to show you their certifications. More often that not, fixing the problem correctly is more costly up front, but best in the long term.
AC is quite simple after you have a basic knowledge of how it works.