It seems there is always something on the farm that needs AC service so I would like to learn how to do more than keep adding freon. Does anyone have a good recommendation? Are there good online courses? Or good manuals, something like AC for dummies? A lot of book on Amazon, but most seem geared for residential/building HVAC. I am not a great mechanic but am able to do most needed repairs but am clueless when it comes to air conditioning. Thanks in advance!
Learning AC Repair
- Thread starter ChrisB2
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Mrcopier
Well-known member
I have often tried to talk my son into doing this. I lost, but great idea, I don’t think it requires many tools, some gauges. The heat isn’t going away, good luck and post what you find. There has got to be online stuff to find
I'm interested as well. I can handle all the electrical stuff, just the rest of it is a problem.
Air conditioning is such a simple process. It all makes perfect sense. Until it doesn’t work at which time it tends to completely baffle me.
chevytaHOE5674
Well-known member
Hayes has an OK book to give you the basics. Worth a read to wrap your head around it. It's a fairly simple system really.
https://www.amazon.com/dp/1563929139?tag=cattletoday00-20
Some of the info in the book is R12 vintage but the basics apply. Some of the pressures and expansion valves are different for R134a but a quick Google search can give you the info you need.
At a minimum you need a set of good gauges, a good vacuum pump, a good precise scale, a "Macs" certificate to buy 30lb pigs of R134a, I like a leak sniffer (but not necessary), and a bottle of nitrogen is handy as well.
If your working on charged systems you really should have a AC machine to recover and recycle the refrigerant.
https://www.amazon.com/dp/1563929139?tag=cattletoday00-20
Some of the info in the book is R12 vintage but the basics apply. Some of the pressures and expansion valves are different for R134a but a quick Google search can give you the info you need.
At a minimum you need a set of good gauges, a good vacuum pump, a good precise scale, a "Macs" certificate to buy 30lb pigs of R134a, I like a leak sniffer (but not necessary), and a bottle of nitrogen is handy as well.
If your working on charged systems you really should have a AC machine to recover and recycle the refrigerant.
Little Joe
Well-known member
I'm an HVAC guy of 22 years, from my experience too many people add freon to their tractor when it's not necessary. A lot of times the coils need a good cleaning. They will blow out their condenser coil but not their evaporator coil, airflow is everything with HVAC. A dirty filter or evaporator coil will give the same symptoms as low refrigerant. Also a lot of guys are charging using low side port only, very bad idea, you need to know that head pressure. I'm not an expert on automotive or tractor ac, my experience is residential and commercial hvac but the concept is the same. Also checking superheat and subcool will tell you a lot about what the system is doing. Superheat is the difference between the low side saturation temp, which is indicated on your gauges, and the low side line temp. Same for subcool, difference between high side saturation temp and high side line temp. I would be glad to help anyone in any way. Like I said, my experience is not tractors so knowing where a component is might be a problem but the way it works is the same principle when it comes to the refrigeration side.
chevytaHOE5674
Well-known member
It can be very hard to get accurate line temperatures on many pieces of equipment because of the proximity to heat sources (think 1000° exhaust manifold), buried lines, also line material.
chevytaHOE5674
Well-known member
Should mention that you should keep an assortment of Schrader valves and caps on hand. They sometimes don't seal after being touched. The cap is a crucial part of the seal.
Also they make a tool to replace the Schrader valves without discharging the system. They are worth every penny.
Also they make a tool to replace the Schrader valves without discharging the system. They are worth every penny.
Just fixed the AC on my Kubota tractor. I had a leak on the low side hose at the crimp were the rubber meets the metal line crimp. (I used UV dye in the system and a blue light to find) I replaced the hose, dryer, expansion valve and done about an hour vacuum at which time I shut off the manifold gauges and came back an hour later and they were still on zero which indicated no leaks. With the vacuum I got all the moisture and air out and then refilled through the gauges. Always check ambient temperature on reading the gauges as it can vary, and the max pressure tells a lot. The most important thing is to not over fill. There is a label that tells min and max freon needed and you need to stay within that. The last can I weigh to get very close. Also, I add a couple oz. of Pac oil to lube the compressor and more if replacing condenser or evaporator as the compressors usually come pre charged. Mine also has a sight glass and you need to see a little not a lot of bubbles in it with the AC going as that shows it is not over filled. Agan I will stress to not overfill and never add a can just out of the blue unless like little Joe said you have already cleaned the filters, condenser and evaporator. Also, it is still a good ideal to attach the gauges and check as it only takes a couple minutes.
AC s is pretty simple to work on, but the problem on vehicles if the evaporator is leaking the dash has to be removed to replace on some. Also the compressor can be hard to get too.
AC s is pretty simple to work on, but the problem on vehicles if the evaporator is leaking the dash has to be removed to replace on some. Also the compressor can be hard to get too.
chevytaHOE5674
Well-known member
After a hour your vacuum gauge was at zero?
Perfect vac is 30inhg. If you vac it down to say 25inhg and shut it off after an hour it should still be 25inhg if it shows zero then you have a leak.
Perfect vac is 30inhg. If you vac it down to say 25inhg and shut it off after an hour it should still be 25inhg if it shows zero then you have a leak.
If it moves after a few minutes, then you have a leak and hopefully it is a big leak because small leaks are hard to find.
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chevytaHOE5674
Well-known member
I vac down and make sure they will hold vacuum for at least an hour. If it moves at all then I go back and look for the leak.
Little Joe
Well-known member
Actually a perfect vac is 500 microns or less, have to have a micron gauge or digital gauges. If you take the EPA test for refrigerant handling that will be one of the questions.
chevytaHOE5674
Well-known member
I've never heard reference to a micron reading in any automotive/equipment related application. Every test I've taken and book I have references inHG.
Just looked thru the Macs 609 complaint book and test and everything is in inHg.
Just looked thru the Macs 609 complaint book and test and everything is in inHg.
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MurraysMutts
Well-known member
It's been a long time since I certified in a/c
The first thing that helps the MOST is understanding what state the freon is in, at any given point throughout the system!
That helps proper diagnosis and so forth. Without understanding what's going on inside the system, your lost....
The first thing that helps the MOST is understanding what state the freon is in, at any given point throughout the system!
That helps proper diagnosis and so forth. Without understanding what's going on inside the system, your lost....
TdJ
Well-known member
Been repairing electrical side of AC for years, have an old R21 heat pump system I needed to recharge. Got EPA certified using an app called SKillCat, free and pretty easy. YT'ed videos that show how to check pressure at various temps and recharge the unit (can share links if you want). Bought the yellow jacket gauge set, fieldpiece for testing caps, learnt how to bypass a failed heat pump board this summer & recently replaced just before it got cold. Whole learning / cert process was worth it.
I have an AC trade school in Houston and we teach a "Fast Track" program for contractors from all over the country
It's 10 days long and about 65% hands on. We can get you enrolled in it if you'd like. There is some stuff on you tube if you just figure out the pieces and parts you want to do but as in everything you tube you will find a lot of hacks and shortcuts up there that are done by guys that kind of know some things to do so just keep that in mind if you attend Youtube University
Little Joe
Well-known member
There are 25,400 microns in 1 hg, to assure all moisture is removed from a system you must reach a vacuum level of 500 microns or less, many manufacturers want 400 microns. Analog gauges are not accurate enough to read that. A lot of people don't use a micron gauge and I have been guilty myself when in a hurry, but that is the correct way to assure all moisture is out of the system and moisture is a problem in a refrigerant circuit, especially with many of the new oils like POE and PAG that absorb moisture. The old refrigerants and oils were more forgiving.
