Automotive Air Conditioning Information Forum

andrew vanis wrote: ↑Tue Oct 24, 2023 5:46 pm

Tim wrote: ↑Tue Oct 24, 2023 2:46 pm

Those were in the test and read differently from each other....How did you know both worked as advertised?

Becasue with a 7.5 CFM dual stage vacuum pump. Depending on the vehicle, time of season, temp, and humidity, we would get micron readings anywhere between 400 and 800.

I'd ask, what answer are you expecting from the members here on why your results may not line up with what the MFG publishes or a perceived result? Maybe you're not asking that and just posting results. If that's the case great. Not sure what that means to the next person. As they could have one if not all the different variables I listed among others.

Tim wrote: ↑Tue Oct 24, 2023 6:12 pm I'd ask, what answer are you expecting

Good question. - I was expecting something that might explain the different readings under same test conditions because it is so weird that a number of gauges, several high end manufacturers, give different readings. Maybe there is something I'm missing because how would top manufacturers get away with such variance? What could it be?

For your conclusion that you had good gauges because they read 400 - 800 -

Did you have a chance to place both gauges on the same system to see if they read the same? Would you be willing to put both of your gauges on your pump and report what they read?

Then there is the more important and harder to test question, does indicated 400 really mean 400 actual?

Below are the results by reading. The closest grouping is D,E,F with only about 100 microns from one to the next one but say the middle one E at 2800 is still 860 higher than A which is a reading 44% higher than A. A is one of the gauges you cited.

My hope was to have a discussion that could explain the results and hopefully bring some experience secrets how to deal with/calibrate/ensure that the gauges we rely on are giving us accuracy.

The purpose of my test was to find gauges that are accurate and of those, see if there were cool features on some or especially good values. They were all between about $100-200 with most around $175 so really not a huge price difference. For features, some of them BT phone/graph which is kinda cool, some have temp compensation options for leak testing, etc. Pretty cool stuff but if the readings can't be trusted, its all for not.

So I guess so far for the reader, one can conclude that gauges, even from top manufacturers, may not be giving accurate results and there is no way to really know.

Gauge Microns Diff from prior lower % diff of this line
A 1940
I 2180 240 11.01%
B 2340 160 6.84%
D 2710 370 13.65%
E 2800 90 3.21%
G 2900 100 3.45%
C 3300 400 12.12%
H 4425 1125 25.42%
F 124306 119881 96.44%

We sold our shop in 2015.

How do I know it worked? We were a business with many different cars over many years using micron gauges. When you start the vacuum pump with a very high range, let's say 8K. And it pulls down to 500 microns. In my book, using top-of-the-line equipment. It's working. I don't need to know anymore. As the gauges would also show, it was pulled into the proper vacuum. Micron level would hold or not, depending we charged the vehicle and sent it down the road.

Tim, ever hear the expression about beating a dead horse. I'm out

hi
Experience of your micron gauge for small leaks eg manifold o ring leak and what u would expect to see on the gauge to represent that

swampy 6x6 wrote: ↑Wed Oct 25, 2023 8:19 am hi
Experience of your micron gauge for small leaks eg manifold o ring leak and what u would expect to see on the gauge to represent that

Thanks for the reply. I cannot follow what you are trying to convey. Can you please restate?

hi
Early in the am probably tired .
Experience with your own micron gauge goes along way . Once u have seen how the gauge responds to leaks of various causes eg r134a coupler or manifold o rings etc . First thing i do if gauge is not performing is to alcohol clean and retest . Once you become familiar with the gauges response ,this goes along way to verify its accuracy .
I vac test hoses 1x at a time .Say 6 hrs each on the pump and asses
I then test the manifold with hoses ,no couples just blanked off and asses
Then attach couplers and try on vehicle and asses

compressor shaft seals can react the same as manifold o ring leaks
Recently I vac straight off the pump with micron gauge on opposite port ,,works better than going via manifold ie more potential leak points

The other day I changed an evap core on gut feeling and sure enough UV dye on the core but not the drain . Even pressure tested and gas detector did not pick it up either . Would the micron test be revealing dont no .
Some times the brain needs to be used .

We calibrate brand new tools all the time. I have had to send out brand new Fluke meters for Calibration stickers before I could use one.

If you have enough cash to buy $1500 worth of gauges, pick one you like and send it out.

Or is this experiment going to produce 8, "open box" used returns that vendors will have to eat?

bohica2xo wrote: ↑Fri Oct 27, 2023 7:04 pm We calibrate brand new tools all the time. I have had to send out brand new Fluke meters for Calibration stickers before I could use one.

Curious, did they tell you how close it was out of the box?