Make: JOHN DEERE
Engine Size: DIESEL
Refrigerant Type: 134A
JOHN DEERE 4400 COMBINE WITH GM A6 COMPRESSOR
I AM SWITCHING OVER TO 134a.
THE CURRENT SYSTEM HAS NOT BEEN USED FOR A LONG TIME. I PULLED A VACCUM AND OVER A 10 MINUTE PERIOD MY GAGES DID NOT DROP ANY. OVER ABOUT 3 HOURS IT DROPPED FROM 29 TO 25. SINCE I AM FLUSHING THE SYSTEM, CHANGING DRIER, CHANING OIL TO DOUBLE END CAP PAG 150 AND EXPANSION VALVE SHOULD, I REPLACE THE FRONT SEAL ON COMPRESSOR, SINCE IT HAS BEEN PROBABLY 6 TO 7 YEARS SINCE IT HAS BEEN USED?
THIS SYSTEM DOES NOT HAVE A LOW OR HIGH PRESSURE SWITCH SHOULD I ADD ONE?
DOES THIS MEAN COMPRESSOR DOES NOT CYCLE?
ANY HELP OR ADVISE WOULD BE GREATLY APPRECIATED.
I might take some time to get down to 29 Hg depending on how much moisture is in the system.
Does the system hold vacuum, gauges don't return to zero when you shut the pump off or isolate
it from the gauges?
Edited: Mon August 25, 2008 at 6:08 PM by MOrbid
Replace the big rear O-Ring in that compressor or it's gonna leak.
WITH THE GAUGES HOOKE UP IT WENT FROM 29 TO 25 AFTER ABOUT THREE HOURS WITH THE PUMP SHUT OFF. I HAVE ALWAY HEARD THAT THE FRONT SEAL ON AN A6 PUMP WOULD GO BAD IF IT WAS NOT USED.
WHAT DO YOU THINK ABOUT NOT HAVING A HIGH OR LOW PRESSURE SWITCH, SHOULD I ADD ONE?
If the pressure was all the way down to zero when you started, assume that there is a leak somewhere. It is more accurate to test under pressure not just vacuum. You can use air, nitrogen, or a small amount of R-134a. Using refrigerant makes it possible to "sniff" for leaks with an electronic detector.
A high/low switch should be added. High pressure situations are very common on off-road equipment as the condenser air side gets clogged with dust and debris. AMA sells a simple HPCO kit that screws onto your high side port and also doubles as a port adapter for R-134a gauges. I think this unit is a "trinary" switch that will also cut out on low pressure to protect the compressor if the refrigerant is all gone.
THANKS FOR ALL THE HELP.
ONE MORE QUESTION, CAN I GET AWAY WITH USING MY OLD HOSES? I HAVE READ ON HEAR THAT THEY MAY LEAK IF THEY DO NOT HAVE A BARRIER? I WOULD LIKE TO SAY WITH WHAT I HAVE IF AT ALL POSSIBLE.
Your old hoses will be just fine, as long as they are in good condition.
Your 70's vintage A6 will probably sling a bit of oil, the nature of the beast. You absolutely should install a HPCO switch, this is required for all 134a conversions.
I would be inclined to flush out the old mineral oil, drain & flush the A6 with the oil you intend to use. Compressor flushing suggestions are located in the FAQ's. Once you clean everything up, add the required oil charge to the sump on the A6, install a 134a compatible dryer, add some dye & put things back together. Evac & charge with 134a.
Charge level should be around 80% to 100% of the R12 charge, depending on the system. Charge the system, & run it for a few days, then use a UV light for a leak inspection. Follow every line, check every fitting. Check the condensate drain on the evaporator. On a 30 year old system, it could leak almost anyplace - or not. Easy way to find out is to try it.
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
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