Baffling Engine Air Conditioner Problem

[bathurstj]

2006 Kountry Star 3910 w/ Cummins ISL 350. Chassis AC worked great until last year (Jan 2012) on winter trek to FL. No cool air, suspected low freon, had a AC repairman look at it, checked for leaks, recharged it. Worked fine returning from winter trek (Mar 2012) Used the rig in September 2012, no cool air. Had my local AC guy look at it, found it was missing an "O" ring, said it appeared it never had one there. Installed "O" ring, recharged it Jan 2013 before winter trek. Never even made it to FL before it lost cool air. Said the heck with it would take it back to him when I returned in April 2013; used the roof mounted AC's with Generator (I believe it to be more cost effective fuel-wise anyway). Each time it was charged dye was installed, no one has been able to find a leak. Just got it back from my local AC guy (who BTW is a good mech and I trust him). He withdrew the Freon, only had 1/2 pound in it. Recharged it and ran it for several hours, crawled all over, under, inside and can not find a leak anywhere. Even put a rag under it to catch the condensation to see if it showed any signs of dye; no joy. He is baffled. I called and spoke with Newmar and they are baffled as well, They said they have never had a problem with the two hoses that run the length of the RV leaking, as they are mounted in the chassis by Spartan and are very carefully wrapped to withstand any rubbing, friction, etc. Thoughts to share would be greatly appreciated by this old retired Marine Grunt. Semper Fi Jim

[dickandlois]

Hi Jim, With your AC service tech checking the system, I would think he ran a vacuum test on it before refilling it with freon.

That just about covers the entire system for leaks.

The one item that can cause an issue and is very hard to find or detect is the high and low points in the systems used to charge and test them for proper operation are the schrader valves and their seats.

A small leak over time will allow the freon to escape. A bad valve or a bad seat that the valve seal sets in can cause the problem and is very easy to miss with standard test and charging setups.

Hope these thoughts help find the problem.

Thanks for your service! Rich.

[bathurstj]

He did do a vacuum test and it held. Thank you for your come back and your comments on service, Semper Fi; JB

[desertdeals69]

With the gauges hooked up it won't test the schrader valves.

[Briarhopper]

That much of a leak would either have to be somewhere you cannot see or somewhere the leaking is masked by other grime/oil/etc.

Not all leaks that leak with pressure will leak with vacuum.

Curious if anyone has used one of the electronic leak detectors on freon??

[bathurstj]

Electronic leak detectors?????

[Briarhopper]

Electronic leak detectors?????

Have seen ads for them like this for example: http://www.ueitest.com/products/ac-refrigeration/rld10

Assume they work, but have never heard anyone speak of using them.

[dickandlois]

Hi Stuart,

Thanks for the link. Took the time just now to look over their equipment line. Interesting and some other meters that they make look kind of neat. I will need to revisit the sight and look at some of the technical data sheets.

Been using the old style manifold for years.

Most shops that know they are dealing with a leak issue due run a vacuum and pressure test on the AC systems before recharging.

The one item that does get over looked are the schrader valves and a leak detector is one way to test them, but good old soap and water will find most of the pressure leaks.

Rich.