Alternative A/C Test Methods

[1987 GMC Jimmy]

I’ve got the smallest A/C leak in the history of A/C leaks and wanted to see if y’all have ever had this happen to you. When the positive pressure slips below a certain point, the leak stops. Not enough pressure to kick on but doesn’t go totally empty. At rest, it reads 20+ PSI on the low, 25+ on the high. This is partially good because I know my new accumulator and o-tube aren’t ruined since it’s not open to the atmosphere, but it’s impossible to find the leak. It takes a few days to a week for the leak to stop. It’ll hold vacuum indefinitely so I know I need positive pressure to find the leak.

I don’t know if there’s enough leakage to register on an electronic refrigerant sniffer that I don’t currently own. I’m very hesitant to use compressed air and soap bubbles in this moisture-laden, Southern air but worry it may come down to that. Nothing found with a UV leak dye, and the R-134a o-rings, adapters are all new. What would you guys do? I don’t want to arbitrarily replace parts because everything works well, especially the compressor.

 

[yevgenievich]

Charge with 134 and try a sniffer. Otherwise inert gas to pressurize the system, but still need some way to identify the leak if it comes out

 

[Doppleganger]

I had a similar issue - added dye and found a seam in my condenser weeping when it pressurized. Otherwise, it would hold a vacuum/charge fine.

 

[yevgenievich]

I had an evap with same issue before. Eventually sniffer picked up on a leak coming from the air vents after sitting for a while

 

[CRM]

Use a sniffer (infrared type is preferred) and if you have no luck then inject it with dye.

 

[fast 99]

Yes on the dye. Our shop doesn't use sniffers any longer. Most leaks today are too small to locate that way. Add dye and charge it up. Use a black light to locate the leak. Usually a 1/4 ounce is enough for a single ac system. Run it for a while, look for visible green. If leak isn't located wait a day, run the system and keep checking. I can assure you it will become visible. Be sure and check the compressor especially on the bottom, use a mirror if needed. Have found many case seal leaks. Try not to spill any dye. Take a hose off or a schrader valve out and if needed hook up a vacuum pump to suck it in.

edit
Also look at the condenser very closely have seen a bunch with small holes or fractures especially at the inlet and outlets.

 

[bucket]

Yes on the dye. Our shop doesn't use sniffers any longer. Most leaks today are too small to locate that way. Add dye and charge it up. Use a black light to locate the leak. Usually a 1/4 ounce is enough for a single ac system. Run it for a while, look for visible green. If leak isn't located wait a day, run the system and keep checking. I can assure you it will become visible. Be sure and check the compressor especially on the bottom, use a mirror if needed. Have found many case seal leaks. Try not to spill any dye. Take a hose off or a schrader valve out and if needed hook up a vacuum pump to suck it in.

edit
Also look at the condenser very closely have seen a bunch with small holes or fractures especially at the inlet and outlets.

I agree with this 1050%. You may not find it right away, but you will always find it with dye.

 

[SirRobyn0]

Yes on the dye. Our shop doesn't use sniffers any longer. Most leaks today are too small to locate that way. Add dye and charge it up. Use a black light to locate the leak. Usually a 1/4 ounce is enough for a single ac system. Run it for a while, look for visible green. If leak isn't located wait a day, run the system and keep checking. I can assure you it will become visible. Be sure and check the compressor especially on the bottom, use a mirror if needed. Have found many case seal leaks. Try not to spill any dye. Take a hose off or a schrader valve out and if needed hook up a vacuum pump to suck it in.

edit
Also look at the condenser very closely have seen a bunch with small holes or fractures especially at the inlet and outlets.

Ya, I still have a sniffer, but it doesn't come out very often.

Remember to check the vents, the floor, even the water that drips from the evaporator if the leak isn't obvious with the die.

 

[GMC trucker]

Insure it’s not a leaking Schrader valve. It’ll hold vacuum for weeks as long as the gauge manifold is hooked to them. That would be a quick and easy fix if so.

 

[Turbo4whl]

@1987 GMC Jimmy If you cannot find the dye anywhere around the system, then the leak is in the evaporator. Locate the condensation drain, and shine the light there. If the leak is in the evaporator housing, the condensation will rinse it to the drain. Remember, black light, yellow glasses on your head.

 

[CRM]

The darker it is during the search the better.

 

[Finkaire]

The leak will appear as an oily spot, dye comes in handy when trying to distinguish one oil leak from another. As said earlier if no leak shows up on the engine side the evaporator would be suspect. Check the condenser and lines for any sign of oil at all. If the system has been retrofitted to 134a and a PAG oil was used, the PAG oil is a corrosive and may have taken out the evaporator, common problem when PAG oil was first introduced with 134a refrigerant

 

[wlwarnke]

If your test ports are vertical(ish) I like to fill them with liquid to look for bubbles. I have fought those damn schraders a lot. Even new ones.

Usually have to depress them a few times with a screw driver (be gentle!) to get them to seal up.

 

[Finkaire]

The cap Is the primary seal

 

[bucket]

The cap Is the primary seal

Actually no. The cap is a glorified dust cover. The Schrader valve (or rubber ball valve in many newer applications) is the primary seal.