AC work

Ey guys i'm scanner danner premium channel subscriber from Brandon MB. CANADA. I'm new with the AC and i just get certified by provincial governement to perform AC work. My question is when the both low and hight sides are Low which are 19psi on low and 30psi on high. Obviusly under charge based upon my weather station. My next move would be recover the refrigirant and perform vacuum. If the gauge stays 28" of mercury or so without changed then i know i don't have a leak or if it does change and drop to zero then i know i have a leak. Then my next move would be pressurize with nitrogen but how much can i pressurize it and are all my steps are right. I need some input from u guys as i said i'm new with this. However i have taken courses how the system works. Just unfamiliar right now how to tackle this and needs more experiance. Thank u all
Pee Jay S.
brandon MB. Canada

I, usually, pressurize with shop air. I pressurize it with as much pressure as I have, 175 psi. Then, I use a soap and water spray bottle and look for bubbles.

Here is ScannerDanner doing this. Start at the 14:00 minute mark.

The video pole71 is fantastic, definitely worth watching.

Personally, I don't put a ton of faith in the vacuum decay test. I've seen many systems seal vacuum but leak pressure, strange as it may sound. IMO, all the vacuum decay test tells you is that there are no gaping holes in the system.

Adding dye to the system (if it isn't there already) while under a vacuum is a good idea, before adding the refrigerant charge. Letting this circulate in the system for bit will (hopefully) make any leaking components obvious. You can also shut the system off to raise pressure on the low side as the system equalizes.

Service ports are always suspect, too. You can test for these by attaching a vacuum gauge to the port itself and watch for pressure building, or use soapy water in the port bore.

Agree with Tyler their, we've got the lazyman's automatic aircon machine at our shop instead of a set of gages, it performs a leak tester after charging the system and if it defects a leak pulls the gas back out. However vehicles rarely fail this test and yet I've had come backs when systems have leaked the gas out slowly under running conditions, the dye is a real help in diagnosing leaks just make sure to check around and clean off any old dye from previous issues so as not to end up chasing your tale. Another school boy error I've made in the past, 2 wasted charges.

Man I've made it sound like I'm solely responsible for global warming....

Rick

Lol people in hotter climates will disagree with me but I live in Ohio and I'm all for global warming!

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I am not a big fan of vacuum testing either , small cracks tend to close up under internal vacuum.
I used soap solution bubble testing a lot when I did LPG conversions but changed to using specialised sprays because soap solution caused brass pipe fittings to tarnish.

What sprays do you use? I have a bottle and brush of leak detect but it's so hard to get to the all the connections an aerosol would certainly be easier.

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PH Gas leak detector spray

See attached normal pressure chart from a typical modern system. The Hi pressure switch on my Mazda is set to open at 484 PSI. You can safely crank up your test pressure to 150 psi, which is more that enough. Nitrogen is best because it does not contain water vapor.
Pulling vacuum on an a/c system main purpose is to get rid of water vapor that gets inside when a component is open or removed. Once total pressure gets to 0 psi, ambiant air containing water vapor will seep inside and will get trapped. If not removed, this water may freeze exiting the expansion valve and clog the tiny orifice, due to low temperature caused by the evaporation of the refrigerant in liquid state, in this area of the system.
Under hard vacuum, water will boil around 40 F, (instead of 212 F at atmospheric, sea level pressure) which is normally below ambiant temperature. This is why it is recommended to run the vacuum pump for about 30 minutes, to get rid of this water vapor. It is also strongly recommended to change the filter dryer.
Vacuum for testing leaks will probably work for cracks due to damage. But, for seals, o-ring and the like, it may not work because these components won't seat the same under vacuum or under normal operating pressure.

If your gonna do a/c work often I would suggest a micron gauge for evacuation. There's a whole nother world below where your gauges leave off. Right now I'm using a bluvac micro,small accurate and cheaper than..well,just cheap. Like, mechanic cheap.

Rockyroad wrote: If your gonna do a/c work often I would suggest a micron gauge for evacuation. There's a whole nother world below where your gauges leave off.

I've heard of using a micron gauge, can you expand on its use? Genuinely curious. Most of the training info I've come across just talks about vacuuming systems for varying lengths of time. :huh:

Right now I'm using a bluvac micro,small accurate and cheaper than..well,just cheap. Like, mechanic cheap.

Hah! We do love our cheap tools, don't we. :lol:

After taking the MACS 609 cert.. ( I think it was 609) I realized there's a lot more to it. So did a lot of research on hvac forums. Basically you want to get below 500 microns were it's REALLY boiling out moisture, close your valves and watch it climb. It will come up, or"lose vacuum" but, you want it to stop hopefully under about 1500 micron. Some people say 800-1000. If it keeps going there is moisture still boiling off. Turn the vacuum pump back on for a little bit and get it back down under 500. If the gauge just keeps climbing you have a leak. I do this after pressure testing,we're most leaks are found.

Thanks, sir. I'll have to do some more research. Is this the gauge you're using?

www.trutechtools.com/BluVacMicro

I have so many questions! :woohoo: :lol: If I'm using a typical HVAC RRR machine, how should I go about installing this gauge? In line with the low side?

Have you found this to be better for detecting leaks than just going off the low side gauge? I'm not a fan of using vacuum decay as an indication of system sealing, but it sounds like this may be more accurate?

I was using a vacuum tree on my pump just to put the gauge inline and be able to ball valve off the pump and shut it off and just watch. However, I discovered a Leakey gauge set and was driving me crazy. So I got a better gauge set. I think next I'm gonna get a valve core tool with side tap to put the gauge on and completely isolate the system from the gauges. I find not so much for leak checking, although it has identified a couple really small leaks, but colder temps from better evac of all moisture, you can "see" it. If you just suck for a certain length of time you have no idea if there's still moisture in there. Search YT for some vids you'll see what I mean, there's a lot of room for moisture before your low side gauge ever moves.

Oh yeah, that's the exact gauge and supplier, good purchase experience from them.
I don't know if you would experience the full benefit of the gauge if your machine is automatic. It probably has a vac decay cycle that's acceptable for automotive much like pcm evap cycles. But not necessarily the BEST for ice cold temps. If you can control your machine manually it will work fine. You can put it anywhere in the system really. I use ball valve hoses and some extra fittings to block things off. I vac everything hooked up gauges, refrigerant tank ect.. the block off with ball valves.

Rockyroad wrote: Oh yeah, that's the exact gauge and supplier, good purchase experience from them.

Good to know.

I don't know if you would experience the full benefit of the gauge if your machine is automatic. It probably has a vac decay cycle that's acceptable for automotive much like pcm evap cycles. But not necessarily the BEST for ice cold temps. If you can control your machine manually it will work fine. You can put it anywhere in the system really. I use ball valve hoses and some extra fittings to block things off. I vac everything hooked up gauges, refrigerant tank ect.. the block off with ball valves.

The machine we have at work can still be worked manually, and still has high/low shut off valves. I DEFINITELY like the idea of maximizing vent temps. I'd need to gather the right fittings to get this gauge to work, but I'm sure it can be done.

I also wondered about potentially saving myself vacuum time? As in, I'm usually vacuuming for 45 minutes after a repair but before recharging. Did it NEED all 45 minutes, or was I just adding to the pump run time? Or, do I need to keep going? It seems like this gauge could answer those questions.

Yep, a very big reason why I started using it. I had issues with a txv system being a little erratic. Long story short it was freezing up(cause like a dumb ass I didn't feel like changing out the drier). A tiny bit of moisture in an orifice tube system not as big a deal. Especially with a/c systems I like to know I got it right the first time and now with the micron gauge, I know. I keep refining my setup to rule out any inconsistencies with gauge readings, that's where the micron gauge really shines. Without the valve core in place you'll get better and faster evac times. I need to buy the robinair core tools with side taps. I have the strap-on set to change the core while pressurized but can't tap on to it.