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I know, I know, it's getting over whelming... Ac questions, ac not working, blah blah blah... But this one flat out has me stumped. Compressor makes a vacuum on the low side, but will not build pressure on high side... Replaced the compressor, dryer, and the expansion valve. High side is at 50-75, low side is anywhere from 0-(-20). Have around four cans in the system, no leaks. Vacuumed the system for over an hour. Held vacuum for thirty minutes. Warmed up the cans to get them in the system. 

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Ac hose coming apart inside causing a blockage?

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7 hours ago, MinnesotaFarmall said:

I know, I know, it's getting over whelming... Ac questions, ac not working, blah blah blah... But this one flat out has me stumped. Compressor makes a vacuum on the low side, but will not build pressure on high side... Replaced the compressor, dryer, and the expansion valve. High side is at 50-75, low side is anywhere from 0-(-20). Have around four cans in the system, no leaks. Vacuumed the system for over an hour. Held vacuum for thirty minutes. Warmed up the cans to get them in the system. 

 I'd suspect Faulty compressor 

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If compressor pulls into a vacuum the compressor is good that’s how we test them. You have a blockage somewhere have to take things apart one at a time and blow nitrogen through them I know everyone doesn’t have it air will work but I don’t recommend. I would start with expansion valve or dryer. Easiest way to tell if ya dryer is to see if line coming out of dryer is sweating. Should be a pressure port in top of cab before expansion valve to see what pressure is there it will be a r 12 or 1/4 flare. But those are the places I would start

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Did you flush the system before vacuuming?? Sounds like a blockage on the low side or at the expansion valve.  

But you would think your high side would read higher.....

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What type of fittings does this have for the gauge set, and does it still have the valves at the compressor?  Are you running an adapter?  Which type?  Pictures of them would help. Sounds like a blockage in the system, but things don't add up.  I'm thinking you have a couple issues, one of which is likely in the adapters you are running. 

 

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Ap air systems conversion kit. Comes with compressor, dryer, and expansion valve. All of which were replaced. Lines have all new stickers on them from about ten years ago. Would think it's hard to believe that it's a blockage because the high side never gets higher than 75. I agree that it isn't adding up anywhere.. I hooked my gauges up to another known good tractor, and they read fine, and fit the same. The fittings are 134 fittings, they are part of the compressor line adapters. 

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Your not removing any heat from system is why heard pressure is staying low hard to believe but basically your just using high side as a tank no different than a bottle of refrigerant. Saw it before. I would start at dryer or expansion valve. Never know expansion valve may have lost charge on sensing bulb or it got a knock it it and lost pressure on power head that’s the round top on expansion valve.

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1 hour ago, Binder686 said:

Your not removing any heat from system is why heard pressure is staying low hard to believe but basically your just using high side as a tank no different than a bottle of refrigerant. Saw it before. I would start at dryer or expansion valve. Never know expansion valve may have lost charge on sensing bulb or it got a knock it it and lost pressure on power head that’s the round top on expansion valve.

Yes I've had brand new dryers dump all the dessicant right into expansion valve. Plugs tight.

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1 hour ago, Binder686 said:

Your not removing any heat from system is why heard pressure is staying low hard to believe but basically your just using high side as a tank no different than a bottle of refrigerant. Saw it before. I would start at dryer or expansion valve. Never know expansion valve may have lost charge on sensing bulb or it got a knock it it and lost pressure on power head that’s the round top on expansion valve.

Very well could be... I'll just have to disassemble everything and start over again. 

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The AC line coupler / check valve behind the left lower front cab light may not be opening

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1 hour ago, MinnesotaFarmall said:

The fittings are 134 fittings, they are part of the compressor line adapters. 

So, they are new lines with the 134 fitting made on them then, correct?  No adapters?

I agree with the other guys that it sounds like you have something plugged up.  I'd say it's a ways down stream or head pressure would be higher.  

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Yes, all updated lines and adapters. No screw on adapters to convert from r12 to 134. 

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11 hours ago, Binder686 said:

Your not removing any heat from system is why heard pressure is staying low hard to believe but basically your just using high side as a tank no different than a bottle of refrigerant. Saw it before. I would start at dryer or expansion valve. Never know expansion valve may have lost charge on sensing bulb or it got a knock it it and lost pressure on power head that’s the round top on expansion valve

I took off top cover of roof panel. Looks like either evaporator or return is plugged. It is frost up right out of the expansion valve, but no temp change in the evap anywhere...

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It’s the expansion valve if you have frost at it

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If you have frost that is always the point of restriction or it will frost if under charged. The pressure is low enough the saturation point of the Freon is under 32 degrees. Best way to charge is with a 30lb can an weigh it in at 85% original charge of r 12. Or charge it to 35 psi on low side with fan on purge. I’m a commercial refrigeration mech so please don’t be afraid to ask or pm me

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20 minutes ago, Binder686 said:

If you have frost that is always the point of restriction or it will frost if under charged. The pressure is low enough the saturation point of the Freon is under 32 degrees. Best way to charge is with a 30lb can an weigh it in at 85% original charge of r 12. Or charge it to 35 psi on low side with fan on purge. I’m a commercial refrigeration mech so please don’t be afraid to ask or pm me

I ran into this problem on a 4440 Deere few years back. With a vacuumed system cans won't always work. My brother had about 10 lbs worth of cans before it would blow cold. We empty the system vacuumed again and charged with a 30lb canister. Correct amount and it was good to go.

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You guys think the brand new expansion valve is the culprit? Isn't it's job to cause the pressure change to creat liquid to gas to evaporate in the evaporator, thus soaking up the heat? 

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That or under charges yes it is supposed to lower the pressure to turn liquid into vapor but if it doesn’t allow enough thru it will cause the problem you described. The evap needs to run above 32 or it will freeze up I would try using a 30 lb can before I would rip it out.

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Should hold a little over 3lbs

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I am positive I have enough in there. If I hott wire the pump, no bubbles in the sight glass, it will flat out not gain any pressure. It just pulls into a vacuum within two seconds. I would hate to say I got a bad exp valve, but who knows... I could always recover the refrigerant and blow air through the evap just to make sure. I don't have nitrogen, I was taught in med/heavy that compressed air is a bad idea, but I don't have anything else. 

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Expansion valve is either plugged or inoperative. Remove it. If there is nothing in it replace it.

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Even though there is frost coming out of the expansion valve? It is started into the evap, but doesn't have temp change out of the evap. 

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Yep it’s lettig some thru just not enough 

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3 minutes ago, Binder686 said:

Yep it’s lettig some thru just not enough 

Ok. Any way to clean them? The last one I took apart and blew air through it just messing around. Could a guy pull the spring and pintle out of this one and clean it too?

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