The coach is in the shop for A/C troubles.
Tech said the unit is empty of Freon, but yet the system held vacuum all night.
Can anyone speculate as to why this can be.
Thanks in advanced.
Maybe the vacuum compresses whichever seal or component is leaking, while the pressure of the freon creates a leak? I would think they need to do a dye test to figure it out.
I have chased that situation before, and as stated above the vacuum will suck an o ring or seal and hold vacuum. Then when pressurized the system leaks. Dye or gas sniffer is what I use to find them.
my Freon leak turned out to be a loose cap for the hi pressure charging port. I must have left it loose after adding Freon.
The charging port cap is more of a dust cover than a cap. Your leak may have been an intermittent issue with the schraeder valve under the cap. When the schraeder valve is working correctly, the system should hold pressure without the cap. I'd keep an eye on it and maybe replace that valve.
I have bought the 2 tools one for R-12 and two for R-134 that change the valve core without losing the freon.
Amazon.com: UTOOL R134A Valve Core Quick Remover Installer High Low Pressure... (https://www.amazon.com/UTOOL-Remover-Installer-Pressure-Conditioner/dp/B07DS77C7D/ref=asc_df_B07DS77C7D/?tag=hyprod-20&linkCode=df0&hvadid=385178051407&hvpos=1o1&hvnetw=g&hvrand=739004591884731562&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=&hvtargid=pla-825705213511&psc=1&tag=&ref=&adgrpid=78533818717&hvpone=&hvptwo=&hvadid=385178051407&hvpos=1o1&hvnetw=g&hvrand=739004591884731562&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=&hvtargid=pla-825705213511)