M7040 Expansion Valve Replacement
- Thread starter beefmaster
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BAP
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Equipment
2012 Kubota 2920, 60MMM, FEL, BH65 48" Bush Hog, 60"Backblade, B2782B Snowblower
Do you have the proper equipment to suck out the gas, then put a vacuum on it afterwards before putting gas back in? Do you have a new dryer too?
Ditto what BAP says.
The new refrigerant has an oil that rapidly sucks in moisture to the system.
The dryer will need replacing as noted.
The system needs a triple evacuation down to 500 microns. Break 1st two evacs with dry nitrogen. You will need a pressure regulator valve for the small nitrogen tank, but the nitrogen itself is even available at Home Depot.
When you valve off the vacuum pump after getting down to 500 microns you can watch the electronic vacuum gauge for moisture coming out of the oil.
Moisture in the oil results in formation of acids which will harm the compressor and the expansion valve. Moisture can also affect the ability of the expansion valve to operate properly.
The new refrigerant has an oil that rapidly sucks in moisture to the system.
The dryer will need replacing as noted.
The system needs a triple evacuation down to 500 microns. Break 1st two evacs with dry nitrogen. You will need a pressure regulator valve for the small nitrogen tank, but the nitrogen itself is even available at Home Depot.
When you valve off the vacuum pump after getting down to 500 microns you can watch the electronic vacuum gauge for moisture coming out of the oil.
Moisture in the oil results in formation of acids which will harm the compressor and the expansion valve. Moisture can also affect the ability of the expansion valve to operate properly.
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Yes, I have A/C equipment - gauges and vacuum. Replaced drier and compressor (after compressor locked up) a while back. My mechanic thinks that when replacing compressor, some gunk got into the expansion valve as it went from working well to not quickly. system was vacated properly, but no nitro purge. compressor hoses are both hot to touch implying that the gas expansion isn't happening in the valve. I'm also suspecting a small leak some where under the seat so will use this to verify. Pressure just seems to vary too much over time. My helpers are and a/c guy and a long time service writer for a dodge dealership and maintains same tractor for owner. Expansion valve isn't expensive so though it would help. I'm more mechanic than a/c guy so am relying on advice by others. I just know that I need the a/c to work!
Even though the drier is new, should I replace it again? Only $25.
BTW, your recommendation of -500 microns is half what the Kubota shop manual calls for, that is -30 PSI, whereas -500 microns is half that. - thoughts?
Even though the drier is new, should I replace it again? Only $25.
BTW, your recommendation of -500 microns is half what the Kubota shop manual calls for, that is -30 PSI, whereas -500 microns is half that. - thoughts?
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Back in the day of R12, you just loaded a can of gas in and rolled.
The oil for R134a sucks up moisture 100 times that of R12's.
It's a three-prong approach for R134a. Vacuum does not remove enough moisture. The drier must be replaced every time the system is opened and is considered disposable. And a dry inert gas is used for additional drying.
Vacuum standard is now 500 microns. However, Tecumseh recommends 200 micron for their products using R134a. Vacuum is to be pulled from both low and high side at the same time. Once pulled down to target (200, 300, 500 micron) wait at least 10 minutes while observing the pressure. Moisture will cause the gauge to go up (towards atmosphere). Because vacuum is not sufficient by itself, dry nitrogen is added to further remove moisture and to break the vacuum for another attempt.
Only after the pressure stabilizes should an attempt be made to charge refrigerant. It may take as long as it takes.
I would try to find that leak before changing the expansion valve. Once the leak is fixed, then replace the components and leak test by pressure from the nitrogen and watching the gauge. Then nitrogen can be released to atmosphere (EPA allowed, no animals hurt during this) and vacuum pump started.
Your A/C guy may need some extra hoses and fittings if he does not usually use nitrogen. Once used for R134a, they can't be used for other refrigerants (because of the oils).
The oil for R134a sucks up moisture 100 times that of R12's.
It's a three-prong approach for R134a. Vacuum does not remove enough moisture. The drier must be replaced every time the system is opened and is considered disposable. And a dry inert gas is used for additional drying.
Vacuum standard is now 500 microns. However, Tecumseh recommends 200 micron for their products using R134a. Vacuum is to be pulled from both low and high side at the same time. Once pulled down to target (200, 300, 500 micron) wait at least 10 minutes while observing the pressure. Moisture will cause the gauge to go up (towards atmosphere). Because vacuum is not sufficient by itself, dry nitrogen is added to further remove moisture and to break the vacuum for another attempt.
Only after the pressure stabilizes should an attempt be made to charge refrigerant. It may take as long as it takes.
I would try to find that leak before changing the expansion valve. Once the leak is fixed, then replace the components and leak test by pressure from the nitrogen and watching the gauge. Then nitrogen can be released to atmosphere (EPA allowed, no animals hurt during this) and vacuum pump started.
Your A/C guy may need some extra hoses and fittings if he does not usually use nitrogen. Once used for R134a, they can't be used for other refrigerants (because of the oils).
Change the valve and pull a good vacuum and not worry so much about moisture. But if you change the valve a d still have problems then you may need a new condenser. Done a few with these new multi flow condenser that when the compressor goes it fills them up with trash and you can't get it flushed out. The result is when you charge it the high side is high and the low side to low and it want cool. I have been doing a/c work only on heavy equipment the last 22 years and when I charge one most get vacuumed down 5 to 10 minutes and then chagred. And only time i change a drier is when compressor gets replaced or its stopped up. I never have any problems with moisture and live near Atlanta and its always humid here in the summer time.
I was unaware oil utilized with R134A absorbed more moisture than mineral oil. I had to replace the reman compressor on my JD 4255 3 times in a short period of time because of a fitting on compressor. I did install new receiver drier each time but I didn't purge with nitrogen during any of the disassembly. My 4255 AC blows cold air.
What's driving the new procedures is minimal release of refrigerants.
Moisture in the new oils forms acids. The acids attack the compressor and expansion valve. So maybe six years down the road the system needs new compressor, dryer, etc. If it had been charged with minimal moisture, maybe it will make 10 years before service.
So moisture will not show (normally not excessive) as a performance issue. Everything cools fine. It's the time between service that is the intent.
Moisture in the new oils forms acids. The acids attack the compressor and expansion valve. So maybe six years down the road the system needs new compressor, dryer, etc. If it had been charged with minimal moisture, maybe it will make 10 years before service.
So moisture will not show (normally not excessive) as a performance issue. Everything cools fine. It's the time between service that is the intent.
Glad you're not working on my equipment.
And if it's done right in the first place with quality equipment, no service required and 20+ years without need to enter the system.
Thanks all, after talking to my buddies - the a/c guy (not vehicles BTW) and the mechanic, the plan is to replace the expansion valve and drier, clean the evaporator since I'll have the seat off, check for leaks - dye and bubbles, draw a vacuum over several hours, recharge and see what happens - hopefully blowing frigid air again! We'll bleed off the existing Freon slowly so as not to lose too much oil, replace an ounce or so. I don't plan on a flush as I don't want to remover compressor unless I have to. I don't see any leaks I the front end so hopefully a new expansion valve (if old one is plugged) will show that the pressure is stable and where it should be.
Next weekend is D Day
Next weekend is D Day
I can't say I agree with your decision not to flush the system at this point, but I guess time will tell.
Hope you come back after a few weeks run time once this is all done and let us know how it all worked out
Hope you come back after a few weeks run time once this is all done and let us know how it all worked out
A few more recommendations.
Check the hoses and see if they are rated for both charging and vacuum. If you are going to hold a vacuum you will need vacuum rated hoses.
After you finish running the vacuum pump replace its oil. Acids from the system will pull into the pump oil and start eating your vacuum pump.
200 microns is the bottom floor for vacuum. More vacuum than that level will change the refrigerant oil which is bad.
Check the hoses and see if they are rated for both charging and vacuum. If you are going to hold a vacuum you will need vacuum rated hoses.
After you finish running the vacuum pump replace its oil. Acids from the system will pull into the pump oil and start eating your vacuum pump.
200 microns is the bottom floor for vacuum. More vacuum than that level will change the refrigerant oil which is bad.
thanks, I may flush, just not sure yet. will need to disconnect compressor but that's not hard at all. Since I'm replacing drier, could also flush condenser - a point where obstruction is common.
So, Jim you're saying don't take it down to -30 psi?
So, Jim you're saying don't take it down to -30 psi?
At -29.9 psi it's not possible to measure accurately using psi. An electronic gauge which will read microns is what is needed. The gauge needs to be away from the vacuum pump and closer to the system, with short hose.
Realistically, I don't think that it will be possible for you to get as low as 200 microns. I think that you will find that after shutting off/ valving off the pump that the pressure will rise. Some of this will be water evaporating, some will be leaks in the fittings and hoses. That is why a good hose set is needed which is rated for vacuum, and keep hoses as short as possible. This is also why manufacturers recommend three separate evacuations instead of one long one.
Keep the gauge up so that oil cannot get into it. If the port gets oil you won't have the accurate readings required.
Also do not use a large vacuum pump to hurry up. It will be counterproductive as the rapid pressure drop will cause moisture to ice up and block the flow.
If you're thinking of flushing you might want to test for acid first. Your A/C buddy should be able to get a test kit at his supplier.
Realistically, I don't think that it will be possible for you to get as low as 200 microns. I think that you will find that after shutting off/ valving off the pump that the pressure will rise. Some of this will be water evaporating, some will be leaks in the fittings and hoses. That is why a good hose set is needed which is rated for vacuum, and keep hoses as short as possible. This is also why manufacturers recommend three separate evacuations instead of one long one.
Keep the gauge up so that oil cannot get into it. If the port gets oil you won't have the accurate readings required.
Also do not use a large vacuum pump to hurry up. It will be counterproductive as the rapid pressure drop will cause moisture to ice up and block the flow.
If you're thinking of flushing you might want to test for acid first. Your A/C buddy should be able to get a test kit at his supplier.
OK, flushed entire system (minus drier and compressor) twice. Replaced drier and expansion valve. When taking out evaporator, the heat sensitizing tube fell out! So, I put it back into the holes I though it came from - plastic prong outside fins, metal one inside.
Fixed small leak but not one I was expecting - it was caused by using skinny O-rings that came with drier, substituted fatter ones and no leak.
drew couple of vacuums and was ready to refill. I don't have a big tank and scale so using 20oz cans. filled up nicely about 1/4 can, but no more. pressure gauges equal around 100 psi. rechecked expansion valve/heat sensitizing tube - no apparent problems.
Compressor will not kick on. mechanic or ac friend coming over this evening to jump low pressure switch in hopes of starting compressor.
Should I keep putting Freon in? thoughts? Trying to do this myself as whisky is getting expensive having buddies over.
Fixed small leak but not one I was expecting - it was caused by using skinny O-rings that came with drier, substituted fatter ones and no leak.
drew couple of vacuums and was ready to refill. I don't have a big tank and scale so using 20oz cans. filled up nicely about 1/4 can, but no more. pressure gauges equal around 100 psi. rechecked expansion valve/heat sensitizing tube - no apparent problems.
Compressor will not kick on. mechanic or ac friend coming over this evening to jump low pressure switch in hopes of starting compressor.
Should I keep putting Freon in? thoughts? Trying to do this myself as whisky is getting expensive having buddies over.
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BTW old expansion valve appeared really dirty with what the mechanic called "black dust" which he believes came from the failed compressor I replaced.