Looking to get a micron gauge for auto a/c

[purplezr2]

If your A/C system can't hold a vacuum for even 10 minutes then there is absolutely NO WAY the system will hold refrigerant. If the A/C machine won't hold a vacuum, then it needs to be repaired. It's hard to properly fix broken cars with broken tools.

I think you missed the point of what I was trying to say.

I didn't say anything about the merits of how long the system could hold vacuum. I was referring to how long a typical vehicle AC machine actually pulls vacuum prior to the filling process.

 

[theoldwizard1]

It's obvious you don't know much about this topic but you still couldn't stop yourself from dropping a smart *** comment. lol.

That's fine. This is a discussion forum. You're welcome to post a comment in any thread on this entire site. But when you make youself look silly, don't be suprised by the replies that you might get. That is all.

About 50 years ago I worked at a large Sears garage. I didn't do A/C work, but I could see the guys that did.

They used standard A/C gauges. They pulled the vacuum down until the gauge read zero. Then they turned off the pump and went on a break or worked on another vehicle. 15-30 minutes later, they add the Freon (yes, it was Freon back then).

 

[atikovi]

I put in 150 psi nitrogen. In half an hour it was at 100 psi. Found this leak at the upper condenser line. I assume it's a bad 0-ring?

I replaced the o-ring and pressurized it again to 175 psi at 7:30 pm yesterday with 76°F. Do I still have a leak or are these readings normal?

9:30 pm 72° 145 psi
11:00 pm 71° 145 psi
7:30 am 67° 140 psi

I can assume the overnight drop of 5 psi is from the drop in temperature. What about the 30 psi drop in the first 2 hours? Is that just the nitrogen migrating throughout the system?

 

[American Locomotive]

pump it back up to 175 and see if it holds.

 

[atikovi]

At 10 am it was still at 140 so that was enough for me. Connected the vacuum pump for 2 hours and just charged it. Will wait an hour for the freon to flow throughout the system before starting it up.

 

[AA/FC]

I think you missed the point of what I was trying to say.

I didn't say anything about the merits of how long the system could hold vacuum. I was referring to how long a typical vehicle AC machine actually pulls vacuum prior to the filling process.

Oh, gotcha... That length of time is typically set by the operator of the machine. Most shops (NOT ALL) cut this time down to the bare minimum (or less) because time IS money. When I do A/C in my home shop I run the vacuum pump for roughly an hour.... sometime 45 minutes..... but I've ran it longer, too. The bottom line with vacuuming an A/C system is this - the longer, the better. There is no downside to letting the vacuum pump run as long as you have time for. And on a side note, the vacuum pump oil needs to be changed frequently in order to acheive those extremely low vacuum levels that on a micron gauge can read.

 

[engineer2]

the vacuum pump oil needs to be changed frequently

My wife's employer sells lab equipment and she can get vacuum pump oil at cost. Bought a gallon and wife said they were puzzled as to what I was going to do with a gallon of vacuum pump oil. They could not fathom someone working on their own vehicles.

 

[AA/FC]

About 50 years ago I worked at a large Sears garage. I didn't do A/C work, but I could see the guys that did.

They used standard A/C gauges. They pulled the vacuum down until the gauge read zero. Then they turned off the pump and went on a break or worked on another vehicle. 15-30 minutes later, they add the Freon (yes, it was Freon back then).

Then you really shouldn't be giving advice or commenting about a topic that you don't know anything about. I mean, you certainly can... but it's obvious to others who do know about the topic..... You might think it's funny to knowingly post BS info in a thread but someone else could potentially take your post as fact and get steered the wrong way.

"Freon" was a brand name trademarked by Dupont Corporation. So yes, R-12 was actually "Freon" if it was manufactured by Dupont. I still have a 30 pound tank or R-12 refrigerant in my shed. It's not Dupont branded so it's technically not "Freon", it's R-12 Refrigerant.

 

[AA/FC]

My wife's employer sells lab equipment and she can get vacuum pump oil at cost. Bought a gallon and wife said they were puzzled as to what I was going to do with a gallon of vacuum pump oil. They could not fathom someone working on their own vehicles.

It's surprising how fast nice clean vacuum pump oil can turn to a disgusting milky gray liquid... I usually buy it by the quart from the local tool dealer. (luckily we have a local brick and mortat tool dealer here in town)

 

[atikovi]

What's this about changing vacuum pump oil? My pump is probably 6 or 8 years old and may have 20 or 30 hours run time. The oil looks like new on the sight glass.

 

[engineer2]

Mine stays pretty clean too, but I only do one to three cars a year. If it get brown or milky, it gets changed. New vacuum oil looks like cooking oil.

 

[428PI]

Right.... but according to "theoldwizard1" nobody uses nitrogen for testing A/C system in the automotive world.

I've never seen it used in the automotive world and I've worked on air conditioners since around 1980 but I'm sure there are some that are. My brother used it on tractors. I used it on my mini split. I'll tell you a little secret that will make some people turn their nose up. We were always told that under no circumstances to use any stop leak in ac systems. Well, my 2003 tbird had a leak and I couldn't detect where it was coming from. I bought a freon detector, used soap and water, didn't try nitrogen though. The compressor was replaced when I bought it and I replaced the manifold and tube assy because one hose was leaking. It was using a can a month or so. I finally bought a little of the stop leak and wouldn't you know it. Added it in 2018. May be a tad low now in 2023.

 

[AA/FC]

I've never seen it used in the automotive world and I've worked on air conditioners since around 1980 but I'm sure there are some that are. My brother used it on tractors. I used it on my mini split. I'll tell you a little secret that will make some people turn their nose up. We were always told that under no circumstances to use any stop leak in ac systems. Well, my 2003 tbird had a leak and I couldn't detect where it was coming from. I bought a freon detector, used soap and water, didn't try nitrogen though. The compressor was replaced when I bought it and I replaced the manifold and tube assy because one hose was leaking. It was using a can a month or so. I finally bought a little of the stop leak and wouldn't you know it. Added it in 2018. May be a tad low now in 2023.

Like we mentioned earlier in this thread.... testing with nitrogen is a relatively new thing. There was really no reason to test with nitrogen back when refrigerant was dirt cheap. That all changed when prices went through the roof

You're right... NEVER use stop leak in an A/C system. That's a good way to make sure your A/C never works properly again. lol. Oh, don't get me wrong, I know if you dig deep enough you'll find plenty of success stories with A/C stop leak, similar to your story..... But that doesn't make it a good product, it just means that you are one of the lucky ones. lol.

I know some guys who own stop leak detection equipment and if they detect ANY stop leak present in a system at all, they will refuse to connect their A/C machine to that system and refuse all A/C repair work on that vehicle. The stuff ruins everything. Including A/C recovery and charge equipment. (potentially)

 

[AA/FC]

What's this about changing vacuum pump oil? My pump is probably 6 or 8 years old and may have 20 or 30 hours run time. The oil looks like new on the sight glass.

A lot of guys never even think about their vacuum pump oil.... as long as the pump works, it's good enough, right? Well, not really.

Just like most guys don't use a micron gauge, most guys think the small vacuum scale on the gauge set is accurate enough to properly vacuum the system. It gets you close. But if you REALLY want to do a good job there is not enough resolution on those analog gauges to see a proper deep vacuum. The purity of the vacuum pump oil affects the level of deep vacuum your pump can achieve. You'll probably never see a difference in vacuum pump oil if you're only using analog manifold gauges.... but you CAN see the difference when vacuuming with a micron gauge. Clean Vacuum pump oil is required to achieve a deep vacuum.

For example:
29.00 inches of vacuum = 25,400 microns = moisture will boil at 80 degrees F
29.95 inches of vacuum = 1270 microns = moisture will boil at 6 degrees F
29.99 inches of vacuum = 254 microns = moisture will boil at (minus) -24 degrees F
(numbers above are pulled from a random chart I found on the internet)

I'm sure some guys will see this post and tell me getting this low of a vacuum on automotive A/C systems is overkill. Well, that's debatable. I had another guy tell me one time that I was a hack for not getting down to the 500 micron level. lol.

I have found getting below 750 microns on a vehicle is hard to do. It is not a hermetic system like a home A/C compressor. The compressor shaft seal on a vehicle always seems to be the weak point in automotive air conditioning. If I can get to 1000 microns then I am generally pretty happy. This is the level that I shoot for when vacuuming and charging automotive A/C systems. It's about trying to do the best job that I can.

 

[428PI]

The stuff ruins everything. Including A/C recovery and charge equipment. (potentially)

That's what we were all told but maybe it's just an ole wives' tail type of thing. Heck, Pioneer who markets my mini split actually sells stop leak for their systems.

 

[American Locomotive]

Stop leak hardens when it comes into contact with air. Many AC systems have leaks that are too large to be stopped by stop leak. Air then gets into the system. Stop leak hardens in the system.

 

[AA/FC]

Feel free to use all the stop leak you like. I don't care...

 

[Milton Shaw]

Remember that you will have to use adapters with micro gauges to hook to R134, and all the other newer models. Those adapters always leak a little from what I have seen. The Fieldpiece with the built in micro gauge does take care of that connection.

 

[pcmeiners]

"Would argon work? I have a large bottle for Tig welding and it would be cheaper for occasional use than buying a nitrogen bottle."

Argon is larger than Nitrogen, not by much. So it is fine for leak testing, especially
considering the 410a molecule is 1000x times the size of nitrogen , most refrigerant gases are very large molecules. Argon is almost 4x nitrogen's price as a 125cuft fill in my town.