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1486 AC


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My neighbor uses his uncle's 1486 and spent "buckoo" bucks on it. I can see the compressor has been replaced but what else I don't know. It is converted to 134a. I cleaned the radiator, first with compressed air then with a pressure washer and it looks very clean. I also shut off both heater hoses at engine and set cab to recirculation and still could only get about 65 degree temp from the vents. So I put my gauges on it and it had 35-40 lbd on low side, about 150 on high side. Is this normal? One mechanic I talked to said to shoot for under 30 on the low side and could see up to 350 on high side on a humid day. The temp ewas about 75 when I checked it, so I figured it was overcharged???? Or does these pressures indicate a problem??? Is there anything that can be done to make these tractors cool better, as our 1086 doesn't cool near as well as my 1586 does??? Thanks, Rob

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What you have sounds pretty normal for 134A on a 70 degree day, between 25 and 30 on the low side would be ideal but where you are should cool just fine. 350 on the high side :blink: thats dangerouslly high 150 (where yours is) is normal. If you see 350 the clutch should cut out on the compressor otherwise somthings gonna blow. The cause of the high pressure is typiclly a pluged condensor.

Now for what you might have, first things first your pressures sound good and you cleaned the condesor. How are the cab air filters? check them they can restrict the air flow through the evaporator and cause warmer than average temps. If they are good and clean check the evaporator, is it good and clean or dose it have alot of dust collected on the fins? If it dose clean it with compressed air also. The evaporator should be located under the roof. If it still has trouble then you have an issue with the refrigeation system itself such as a bad expanssion valve, or a saturated reciever dryer if it has one at all. Once you eliminate the simple stuff you will need to recover the system and go from there with testing.

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Welcome to the wonderful world of retrofits....lol

There are a number of things that could be wrong....

First thing I'd do is pull the roof cover off and check to see if the foam sealing strip that seals the core to the roof hatch is still there and in good shape. Lots of times those are missing and that allows the air to bypass the evaporator core.

Also check the location of the sensing bulb for the expansion valve (if applicable - later serial numbers used a block type expansion valve that was bulbless). Make sure it's in good contact and properly wrapped with insulation tape (dum dum).

Next thing is to fire the tractor and AC unit up with the roof cover off....check the evaporator core's temp as well as the frosting pattern on the core. If you have a core that is only partially cold or froze you could be looking at a undercharged system.

134 typically runs much higher pressures then r12, especially under high heat/humidty conditions. Compare temp/pressure relationship charts for both r12 and 134 and you'll see what I mean.

The new replacement high side cut out switches that CNH provides have a higher cut out pressure to guard against unnessisary shut downs due to the different refrigerants higher pressures.

Hopefully the tractor had a complete new set of new style barrier style hoses rated for 134 installed when it was retrofitted....otherwise you'll always be chasing leaks. Typical retrofit will involve all new hoses, new expansion valve, receiver/dryer, and complete flushing of the cores. The old style pumps (square york style) are very prone to shaft seal leaks even with brand new replacement units. The higher working pressures of 134 accelerate shaft seal leakage even further....a Sanden replacement unit is highly recommended.

If I had to venture a guess at this point....if the tractor cooled properly when it came back from the ac shop to begin with.....I'd guess you looking at a low charge of refrigerant. Ambient temps that you are talking about will generate high side readings of 200-225psi in my experience (in our area/elevation at least).

Let us know what you find out when you pull the roof hatch off.

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Thanks, guys. I am just a young farmer trying to help out a few neighbors for a little extra cash. The only school I went to was the university of hard knocks. I learned what I know from my dad when we repaired the junk we have and some from working at a Ford dealership for a year and a half, so I definitely don't knoe it all and very much appreciate your help. I'll check the evap core and see what it looks like. If the cab is on recirc, is there a filter? The hoses were not replaced. I'll check further later today maybe. Thanks, Rob

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