AC Leak detection

[dkamp]

I have a slow leak in my AC. (Not factory, This is a Vintage Air System). A visual check looks all good, no oil residuals I could find. Since I could not find any potential leak points anywhere, I replaced the O-Rings in every connection I could physically get to.
I then pulled a vacuum for 30 minutes and after turning the vacuum off, the gauge was reading 19 In Hg.
After 30 min it leaked to 12 In Hg. after an hour it was down to 8 In Hg.

What is a good method to track down this slow leak?
Is there any options other than adding the 134a and using a detector?

 

[OCG]

That's a big leak if it's losing more than half within an hour. I think you have to go with the leak detector if you can't see or hear it. At that rate of loss I would think there would be an obvious culprit. Have you tried listening for it (in areas you can't see)? How about the compressor, you give it a good look over?

 

[dkamp]

After digging in a bit, I found it was the AC Gauges that caused the leak.
I used one can of 134A to pressurize the system, then sprayed a dishwashing solution on the fittings and found that the High side quick release And the yellow line at the gauge was bubbling a leak.
The interesting thing is when I took the gauges back to AutoZone and attempted to warn/alert the guy about the leak, He said "Well what do I expect for a Free tool loan? hmmmm. (Dedicated employee of the month material).

 

[AMC Diplomat]

After digging in a bit, I found it was the AC Gauges that caused the leak.
I used one can of 134A to pressurize the system, then sprayed a dishwashing solution on the fittings and found that the High side quick release And the yellow line at the gauge was bubbling a leak.
The interesting thing is when I took the gauges back to AutoZone and attempted to warn/alert the guy about the leak, He said "Well what do I expect for a Free tool loan? hmmmm. (Dedicated employee of the month material).

Autozone is the worst these days