Air Conditioner

working on a john deere 4040 tractor air conditioner. system is 134A but is has only 5 lbs on low side, compressor will not turn on. How do i get the compressor to cycle?

What psi is on the high side?

Well the smart butt answer would be... Fill it with freon!!!! The low side will never be below 30-40 PSI on a completely charged system. IF it is at 5 psi when the compressor is not running then it will drop to zero or lower when the compressor kicks in.

If you are filling it you really should have a real gauge set not just those little throw away low side guages you get at the Auto supply stores. If you have a guage set and are filling it out of a thirty pound can then just open the low side to the can and start filling the system. It will pressurize enough to get above the low side switch. If you are using the little cans it still should not need the compressor to be running when starting to refill the system.

If you do need the compressor to run then just take a jumper wire and hot wire the AC clutch engaged. BE CAREFUL and don't put too much in while you have it hot wired because the high pressure switch is out of the circuit too while it is hot wired.

High pressure is 0.

Thank you. Yes, trying to fill it with freon, but don't have a bottle, just cans. Have a guage set and was trying to get the compressor to come on to charge up enough to kick on. tractor AC has not been used in couple of years.

I usually just empty at least 2 cans into the accumulator (liquid can upside down) then start the engine, turn the air on high and continue. The compressor will run longer and longer as the system gets full. Most 134a systems will stop taking freon when full.

Hello JD4040,
I would not count on the system to stop taking freon when full AUTOMATICALLY!. 134A runs a lot higher presuures then old freon systems.The charge and presures both depend on ambient temperature, and charge the system with vapor only when running!
Post the ambient temperature and i'll post the pressures in 5 degrees F. increments.
Guido.

Did the system have 5 Psi before you started??? If it did you MAY be able to just charge it and have it work. Systems usually have leaks and will not hold the high pressure. They will leak down so far and quit working. Then they will hold low pressure for a long time.

When you get it full check all the fittings and lines for leaks. Spray bottle with dish soap and water works fine. The usual problem is the cab corner lines on the left rear cab post. They are wrapped in insulation. That holds moisture in and they rust through. On any tractor that is 15 years or older and still has the original line I just replace them before even trying to get the system to work. 99% of them are rusted. So even if they are not leaking now they soon will be. Started doing this when R-12 got expensive and have kept doing it. I have fewer recharge calls since I started doing this.

On my own tractors I have two that we use only in the spring and fall. These have slow leaks, usually takes them a month to leak down. I just charge them up and run them. So far I usually have enough reclaimed freon that it is not costing me too much to do it that way.

DO NOT put any of that freon stop leak in the system. NEVER EVER use it!!!! It will mess up the compressor and expansion valves after it gets some age on it. Plus it will ruin anyone's tools if they try to repair the system later without flushing it. Good friend messed up his reclaimer on the stuff. If I find it I replace all the lines, compressor, have the condenser and evaporator sent out to a radiator shop to be boiled out. The owner just made a line repair cost himself big money!!!!

GUYs understand that most repairs in a can are just SNAKE OIL!!!!!

(quoted from post at 08:30:35 06/25/12) Thank you. Yes, trying to fill it with freon, but don't have a bottle, just cans. Have a guage set and was trying to get the compressor to come on to charge up enough to kick on. tractor AC has not been used in couple of years.

Click to expand...

A system that has been down for two years should be vacuumed free of moisture. As the system leaks, any filling will be a temporary stop gap measure. It's time for at the minimum of rePlacing o'rings and the dryer receiver. Odds are there is a leaking line and a failing comPressor seal.

Temp. will likely be around 95.

Yes it had 5 psi on low side when i first put the gauges on, 0 psi on high side. The system is only about 5 years old. I will need to figure out the leak, but i was hoping to get it charged and last for a month or so before taking it to someone to get it fixed.

Hard to read 5psi on a high side gauge.
System should be equalized on one that hasn't been run for a while.

Sounds like it is out of freon and the thermal fuse next to the compressor is probably blown. These tractors do not have a low pressure switch and will run with no freon until the thermal fuse burns out.

The bozos at the lube shop "checked" mine last year and broke the low pressure port, so all the juice leaked out.

When I tried a can of recharge/lube/leak-stop, the compressor would not run. I had to hold the trigger for a LONG time with the can upside-down, then suddenly the compressor started clicking on for a second, then two seconds, then five seconds, then ten seconds, until it finally ran constantly and the needle showed in the high green.

Of course that all leaked out again in 3 days. Busted schrader valve. Had to get a pro to change the valve, vacuum out the air and moisture, and recharge with a real manifold.

Hello JD4040,
At 95 degrees F. the low side should be between 50 and 55 P.S.I.
The high side should be between 275 and 300 P.S.I. Both sides of the system needs to have a gauge on the service ports while charging..
Remember to charge through the low side, gas only(CAN UP), and keep shacking the can as the refrigerant goes in.
Let us know how you make out,
Good Luck....................Guido.

Just remember..any time the compressor is not running when the Low-Side Pressure is 50, it is NOT because of any need for R-134..
Above that and many will kick the compressor OUT..

Ron..

Amen ,,that stop leak /sealer is death to charging/ reclaimer machines. I use an identifier kit to see if there is sealer in it , also ask customer ,,if there is it's big bucks to straighten system out right . Also on nother post here
,,R134 systems will NOT stop taking freon when full ! Unless you call blowing the pressure valve off on the compressor .

put 4 cans in, pressure around 25 and 250 at around 90 degrees. 55 degree air coming out vents but tractor was in shade. tried to check for leaks with soap/water in bottle but not finding any(took the roof off and checked up top). shut down for awhile and system leveled out at around 95 psi on high and low.

That is only true if it has not been updated to R-134 compressor or had the thermal switch removal kit installed. 90% of the tractors around here have the thermal fuse removed and the update kit installed. The up date kit does have a low pressure switch.

The system is still not full. The low side should be up around 50-55 PSI even when the compressor kicks in. You need to add a little more. It also should have a sight glass by the re-dryer. You may not be able to see through it.

Hello JD4040,
Now that you got it working, here is what you do.
Put the fan at its highest setting, monitor the temp out at one of the vents.Keep putting freon in it as long as the temperature keeps going down or you reach 55 Lb. on the low side and 275 Lb. on the hi side.
Guido.