Hi Guys

1978 Pace Car L82 Auto

My A/C has been regassed, but only blows cold air for a couple of weeks, then eventually blows "less cold" (is that a thing) air until it's not blowing cold air anymore.
Back to the regas guy and he confirms the gas has indeed escaped.
Once regassed - back to nice cold air

This has progressively been getting worse over the last 5-6 years, in terms of the time between regassing has been decreasing - it used to be ok for the entire summer season and then regas the following year, but now it can't last more than the 2 weeks.

The odd thing is there SHOULD be evidence of the gas escaping, but there isn't.

This has my A/C guy and me stumped.

The Compressor is a replacement about 10 years ago, everything else is standard.

Just to confirm once regassed, the A/C works great.
It just degrades over time (now a very short time)
Then regas it, and its good to go again.

Any hints as to where to begin looking would be appreciated..

One thought I had, is if it's escaping inside the cabin, then we wouldn't necessarily see it?

All help appreciated!

 

My 81 did the same thing. The leak was a schrader valve.
Have him install UV dye, or get a sniffer, or find a better guy.

 

Try putting a sniffer sensor right under the compressor shaft. Also, try sticking the sensor in an a/c duct while its running to check for a hard to find evaporator leak. Schrader valves, as Big2bird said, are likely suspects.

VS

 

Don't waste your time with sniffers, they are obsolete.
The system needs recharged and uv dye put in.
Has it been upgraded to R134a? If so, have the lines been replaced with barrier hoses? Non barrier hoses will allow the R134a molecules to pass through the hoses and crimps.
Since you say this problem has been getting worse, I would suspect your 10 year old compressor may have a shaft seal leak. Just speculating there.
Once the system has the dye in it, run it for awhile. Could be 15 minutes, could be 15 days, but the dye will show at the leak points.
To check for evaporator leak, inspect the condensate tube for dye.
Also check the condenser core for pin holes.

As a side note, in my neck of the woods, it is illegal for me to re-charge an ac system I know to be leaking.

Good luck.
Jeff

 

I would also caution that your oil may be very low..most leaks are seen from the oil coming out..until you have none left after multiple charging without readding oil...
if you have not used gauges and just add...
i suggest pull out all vacuum, adding a little oil wont hurt..maybe even a flush..and start over..
assumes r134
also check your hot water shut off valve

 

Thanks for the replies guys - all very helpful

The refrigerant has been changed to the latest spec, so the "barrier hose" may be an issue.

Do any of the parts sellers: Wilcox/Ecklers etc sell a complete kit of "Barrier hoses" for a 1978?

I do recall we put dye in the system to look for leaks, but nothing was ever visible - so its either leaking in an inaccessible location or the gas is permeating (right word?) the original hoses...

More thought time and investigation required

 

I agree with jeffw

if oil in system it is where its leaking...very hard to see sometimes especially condenser..
again replace schrader valves ...
my compressor ran but oil was non existent..and was starting to shred

 

Never heard of 'barrier hoses'?? That is a new one on me.
Recently fixed brothers sube AC. Was a dried hard oring. Dealer wanted over $400 to fix. Has AC guy stumped?? As mentioned time for a different guy.

​​​​​​Put some dye in it. Evacuate and recharge. Autozone loans a UV leak tester

 

There is a good 90% chance it’s the front seal on the compressor. It will progressively get worse as your describing.
eventually you’ll see oil on the underside of the hood directly above the compressor.

 

?? You think if that was the case they could have found that leak then

 

if it’s bad enough, yes, but it usually leaks in operation the most. Not in operation it may not leak at all, or at least not detectable.
i’ve has several front seal leaks, most were not detectable until it got pretty bad.

 

sounds bad as fast as it is leaking down from his description

 

Your AC guy can check just about every component of the system except the evaporator coil with a soap and water spray bottle solution (I go to the dollar store and buy a bottle of kids blow bubbles) once the system is pressured up. You can eliminate just about every component except the evap coil this way. You have a couple options with the evap coil, you can make up a jumper hose with the needed fittings and pressure up just the coil and let it sit and watch for a pressure drop over time or get a GOOD leak detector (professional) pressure the coil up and let it sit over night then without turning on the ignition (don't want to have the blower start up) drop the detector wand into the vent closest to the coil, in the drain tube or pull the fan speed resister pack and stick it through there. A GOOD detector is the best option for finding leaks in an AC system and the fastest way when used correctly. Some leaks can be hard to find but stay with it and you'll get it. I have seen hoses that have become perforated and the soap and water solution was the way I found them, spray the entire system down and let it sit then look for foam to form at the leak.

Blowing the charge, evacuating and re-charging without fixing the leak is not the correct way to do it, fix the leak and it will work when needed form now on.

Neal

 

The compressor seal will generally have the tale tale sign of oil on the front of the clutch and on the underside of the hood if leaking, especially if leaking as bad as you describe. The compressor maintains a good bit of oil so when it starts leaking it usually has an oil patch at the leak.

Neal

 

My 'guess'..... bad Schrader valve with small leak or slightly cut/sliced O-ring at one of the fittings. But, the UV dye will tell all !

If the leak is thru the hose[s], they should show some faint indication of color under UV light (only) on the pressure-side hoses {this would be a new one on me, BTW}.