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Allis Air conditioning

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Hurst

07-24-2005 18:16:27




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I have an allis chalmers 7000 with r134 A/C. Now that it has gotten to be about 95 degrees, I am noticing that the A/C isn't cooling too well at higher rpms. It cools a little better at lower rpms, but not too well there either. I have kinked the heater hose, so will try that out tom, see if it makes a difference, when it is hot that is. With just a low side pressure guage, I have about 10-15 psi after adding 1 can at higher throttle. At idle, I have about 20 psi. Would it be safe to add another can to get it up to about 35 psi?

Thanks
Hurst

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NC Wayne

07-24-2005 19:38:48




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 Re: Allis Air conditioning in reply to Hurst, 07-24-2005 18:16:27  
Ten to fifteen psi on the low side in a R134 system is quite a bit low. The pressures are gonna vary somewhat depending on the system, as well as the outside temp and the humidity. I checked one of my shop manuals which has a chart for the "average" pressures in a 134 system and here's what it says. I'll give you the readings at both 90 and 100 degrees and you can hit a happy medium for 95. At 90 degrees, low humidity, low side is 31-37, high is 170-220----with high humidity the readings are 37-45 low and 210-290 high. At 100 degrees low humidity, low side is 35-44, high is 195-245. With high humidity, low side is 38-48, high is 230-320. Check the pressures with the engine turning at high idle, or at least 1500 RPM. The reason it's cooling some is at a lower speed the compressor isn't sucking as hard and the low side pressure is higher so the clutch is probably cutting in and out on the compressor allowing it to cool for a minute before the pressure drops and the safety switch drops it out. At high RPM the compressor is sucking harder so the pressure drops lower/faster and the safety switch keeps compressor clutch from engaging. For a quick fix you can add enough to get it back to working again, but if the pressures are still that low after adding a complete can the system probably has a pretty sizable for that much to be gone. I'd have it leak checked and also let the guy opened it up and have reciever drier replaced. If the pressure got low due to a leak then refrigerant leaking out also means moisture can get in, so the dessicant in the drier is probably saturated. A new one is probably gonna run you $50 to $75 (give or take) and that's a small price to pay for the insurance it's right. Good luck.

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Hurst

07-24-2005 20:09:27




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 Re: Allis Air conditioning in reply to NC Wayne, 07-24-2005 19:38:48  
I will add another can, then see what it does. I don't know much history on the tractor, so as far as I know it may not have been properly filled when the conversion was done. If this doesn't help with the cooling and the pressure drops, then I will get some dye and find the leak, then see what I need to do then. Thanks for the help. I added some of the stuff with a little oil and leak stop, so that may have helped seal up some o rings that dried out from lack of use? Thanks for the help.

Hurst

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JMS/MN

07-24-2005 20:36:20




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 Re: Allis Air conditioning in reply to Hurst, 07-24-2005 20:09:27  
Is there a shutoff valve on the hose that goes to the heater? Might be open.



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Hurst

07-24-2005 20:49:19




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 Re: Allis Air conditioning in reply to JMS/MN, 07-24-2005 20:36:20  
there is a valve in the top of the cab, but before I open that up again, I kinked the heater hose to see if I get any results? It started to get noticeable when a)weather got hotter and b)after I turned the heater on to unfreeze the evaporator. Thanks

Hurst



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