Automotive Air Conditioning Information Forum

Ordered one of these gauges,



Where do I mount it? Between the high or low service port and gauge set hose? Between the high or low gauge set hose and the manifold? On the hose to the vacuum pump?

I usually mount a gauge like that at the vacuum hose connection on the manifold.

That way I can start by checking the hoses and manifold for leaks before I connect to the system. As well as checking the vacuum pump itself.

Valves shut, manifold and valves are under test. Note the maximum vacuum your pump will pull.

Open the low side manifold valve with the service connector valve closed and the vacuum reading should return to the previous vacuum level if there are no leaks.

Open the high side manifold with the service connector valve closed and the vacuum reading should return to the previous level.

hi
1/ on manifold
2/ either the high or low port , vacuum thru the other port and via a dedicated vacuum hose .

My next micron gauge will have decay rate also . Allows u to be more accurate for micron rise .
CPS do more than one
Blue vac do 3 or 4


Hose quality/condition and diameter all will effect time required to get down to below 500 micron . A dirty hose is a hose not used for vacuum only
Beaware of what your vacuum pump can do ,ie check with micron . A good pump can pull 5-50 microns fairly quickly in minutes . Nothing else connected

My new set of analogue gauges get well below 200 microns once I had worked on them ......
** Its easy to see a leaking set of gauges with a micron gauge ,fluctuating readings when operating the taps
I recently upgraded mine big difference ,,at first the set could not get below 400mic so I removed the valves and applied silicon grease to all threads . Evacuated again microns stayed up so then I flushed gauge set with liquid refrigerant vac again all good microns 200 falling .

Vacuum test with an empty tank as doing the gauges by themselves a micro leak will cause a rise easily .

My friends who have Field Piece set praise them for good sealing etc etc but 5x cost

hi
its easy to get the sensor in a micron meter dirty . Use 99% isopropyl alcohol fill tip with syringe install cap shake once and empty . Let dry for awhile

I noticed that the pictured micron gauge apparently is set up for MVAC R-12 systems and also (I believe) residential A/C systems, which means it has quarter-inch flare fittings that won't work with MVAC R-134a and R-1234yf systems. Therefore, you'll have to purchase the appropriate adapters to use it with the latter two systems.

Got the gauge and connected it directly to the vacuum pump. After 15 minutes it reads between 7600 and 8200 microns. Isn't that too high? Should I run it longer?

This video says a pump can get down below 200 microns in seconds,

https://www.youtube.com/watch?v=z5LbUOWPHMk

"This video says a pump can get down below 200 microns in seconds,"
Correct.
Surely you have an air leak somewhere. Also, the oil level is low. Strongly suggest you change the oil, also, because it is most likely saturated with water vapor, and thus will not pull down very low. Be sure to use oil that is rated for vac pumps, it is special.

To test your system, you start with the gauge directly on the pump as you have done. The you add in components one by one and see what the microns do.

Not sure what I did before, but tried it again and got it down this low in a minute.

Next I put the gauge on the hose where it would meet the charge port. Got down to 360 microns in 5 minutes and after 15 minutes it was still the same. Shut off the pump and after 20 minutes it was still the same.



Will leave it like that and check back in morning.