Finding A Leak In A New System

[philipswanson]

I have virtually a new Trans Air system (all components rebuilt) in my motorhome. But when I evacuate, I get negative 28 pounds but it won't hold when I shut the suction line off on the gauge manifold. It gradually falls to 0 in about 3 minutes so I have a leak somewhere?? I don't have a recovery machine so I am wondering if I can put positive pressure on the system which might make this leak show up with a soap solution. Short of wasting a bunch of refrigerant, anybody know how I can track down the leak? The system is still empty except for the oil charge. Any tips?

[B52bombardier1]

A soap solution will hopelessly contaminate your system. Use some refrigerant with an ultraviolet dye color chemical in it. Charge the system and then use a UV light to see the leaky location.

Rick

[Cusser]

First make sure that the vacuum pump to gauge set connections, gauge set itself, and the hoses are not the problem.

[philipswanson]

I was not planning to contaminate the system. The plan is to put positive pressure on the system with shop air and spray the outside of the system with the soapy solution. Don't want to charge because I don't have a recovery system and all refrigerant would be lost.

[bohica2xo]

An ounce or two of refrigerant should give you plenty of pressure for a leak test. No need to fully charge the system.

Manifold valve leaks and service hose / connection leaks happen occasionally. More common on rental / loaner units...

[philipswanson]

I put a positive charge of pure nitrogen in the system of 60 pounds and sprayed down the connections with soapy solution. Nothing showed up but even the nitrogen charge gradually leaks down. Apparently it's a slow leak which is hard to find.

[Dougflas]

Did you disconnect the hoses from the fittings? You may have a leaky coil and need a sniffer (electronic) and some refrigerant and N2.

[philipswanson]

First make sure that the vacuum pump to gauge set connections, gauge set itself, and the hoses are not the problem.

I think this is my problem. I disconnected the manifold, gauges, etc. and put direct gauges (other ones) to the fittings. It is holding steady at 65 psi of nitrogen. That tells me it's not in the system but in the manifold hook up somewhere, I think. I put new valves on the manifold set up so we'll see what happens when I go back to evacuating the system.

[Cusser]

I've purchased new seals for my gauge fittings in the past.

[philipswanson]

Does your manifold/gauges take special o rings other than the a/c system itself?