Allis-Chalmers 7050 air conditioner

The original Frigidaire pump went 40 years, now smoking a pump once a year. The service man is installing pumps about 2/3 the length of the original... installed 1-wire internally grounded clutch, eliminating a little sensor on the condenser (I dont know what it does, other than it was the other half of the clutch circuit ).... changed refrigerant to 134... new dryer... new expansion valve. When he fixes it, it works... for awhile. Can the size of the pump be altered for this system? Anything else I should be looking for? Thanks Fritz

Are the high and low pressure switches present and working correctly or is it relying on the old style superheat switch?

Dave

I didnt think it would work at all if the switch was bad, but Ill ask him. I didnt want to mess with anything someone else worked on until he had a chance to do his own diagnosis. Cant believe it can have 3 bad pumps in a row... got to be something else wrong with this thing

I do not want to come on to strong here but you or your ..service man.. need to follow the common theme repeated here often; trouble shoot first then apply parts as needed. I am doing a lot of assuming here which can lead to trouble as well. This is because I do not know the exact configuration of the A/C system on that tractor. A sensor ..more like a pressure switch.. on the condenser monitors for high pressure. When a certain pressure is reached it opens the circuit to the compressor clutch. This helps avoid over pressure of the high side of the system as well as over load of the compressor and clutch. Being a tractor from the 70s it would have had an R12 system so I am guessing it has been converted to 134A. So even though 134A will work in the system, it is a fact that it raises the pressures in the system which adds additional strain to the clutch and compressor. If the ..sensor.. he took out of the condenser was for monitoring high pressure he needs to reconnect it. There is a possibility that switch needs to be replaced with one that has a higher pressure spec to avoid nuisance kick out of the compressor due to higher operating pressure of 134A. Also on a 134A converted system it is HIGHLY important to keep the condenser clean and the airflow across it at the optimum of its design. Doing that helps keep the high side pressures down. So there can be no hydraulic leaks up front on the coolers or steering lines collecting oily dust. Now Dave has a legitimate question about if the system is utilizing the ..Superheat switch.. that is a hole different ball game.

They should be changing the receiver dryer each time the compressor is replaced. Also when it was converted to r134a they should have flushed all system components individually. Id have flushed everything each time the compressor got changed also to guard against the possibility of system contamination. If you need to borrow my books text me Ive got a reprinted factory shop book for that series tractors.

Dave

Rereading your original post eliminating a sensor on the compressor thats likely the super heat switch lacking that the system NEEDS a set of high and low pressure switches to protect the compressor from damage otherwise the thermostat in the evaporator is the only thing wired to the compressor circuits and that wont protect from damage. My 7040 has high and low pressure switches and the Deutz 130-06 runs a super heat switch. Both work but I prefer the high and low pressure switches as I feel they provide more protection for the system.

Dave

Thanks Dave Ill pass that along to the owner and the service man. On unrelated subject, the owner got rid of his cows a few years ago and still has all the milk equipment; didnt know if you would be interested in any of that stuff. Hes about 6 miles from you.

At the moment Im not I need of any more milking equipment but Ill keep it in mind. Also I havent been over to see if the Claas square baler is still sitting.
Dave

I would also suspect the condenser is partially clogged or harboring shrapnel from failed compressors.

The entire system must be thoroughly flushed any time a compressor fails. The first place debris from the failed compressor go is the condenser, often trapping it in a manner that can't be removed by flushing.

If there is room, go with a larger condenser, it will work better with 134, and if it is prone to clog with chaff, even better. And do install a high-pressure switch.