Automotive Air Conditioning Information Forum

Morning y'all. I've been browsing HVAC forums and many pros vacuum down systems without a manifold gauges. Why you may ask? The reason is to minimize all potential leak points. Leaks can occur at every seal, every connection and a manifold has many connection points.

I'm wondering if I can vacuum and fill safely without going by high/low gauges (eliminate the manifold entirely basically. I have a micron gauge and am filling by weight anyway.

Buy a quality set of gauges and this won't be a problem.

Tim, thank you. I bought quality tools to do the job once but I tend to err on the OCD and anal-retentive side of things. Maybe that's why my sleep has been s#it lately

I bought all new for my AC overhaul:

-JB Industries Platinum DV-85N 3cfm two stage vacuum pump
-Yellow Jacket R134a specific 3-way manifold gauge set
-Appion MegaFlow vacuum rated hose with VCRT
-Appion AV760 Micron gauge

I figured buy once, cry once applies for MVAC/HVAC as I have mini-splits at home I could use these tools on.

Using a micron gauge is a great way to monitor the precise vacuum while evacuating a system. I use one all the time. But I wouldn't want to forego a good manifold gauge set while servicing a system to monitor both low-side and high-side system pressures while charging and afterward. It will tell you a lot about whether the system is working properly. In my opinion, it's an important diagnostic tool that shouldn't be eliminated.

Appreciate the insight John, will go ahead and do it the conventional way with a manifold gauge set!

I went ahead and vacuumed down the system last night and recharged the system. It's working great and I am getting 40 degree vent temps and pressures on manifold appeared normal during the recharge.

Now I screwed up when I went to fill with the second can of straight R134a. The first can I purged the primary line right where it meets the manifold and got my hand blasted with refrigerant! Fortunately I had thick gloves on. Now when it came time to connect the second can, I forgot to purge the line again.

Essentially I sent a line of air into a system I prepped long and hard for. Everything is working great (for now) but how detrimental (generally speaking) is a line of air going into the system? I'm hoping to keep the car for a few years so if the AC system can stay solid for 45K miles, I'd be more than happy. This was a great learning experience for an amateur like me so big lessons learned for all future work!

EDIT: I just realized I got no air in!!!!!! Since I was using R134a cans with the self-sealing cans (not sealer inside formula), the can tap does not allow air in as I simply screwed the first one off and then next one on. How did I realize this?! I just went to unscrew the main charging hose from the manifold (other end of hose connected to self-seal can tap) and I got a nice blast of refrigerant to my hand again.