Usage:
Air Conditioned Caterpillar Machines Equipped With R-134a Refrigerant
- SUPPLEMENT: 10/31/94
Service Magazine; August 22, 1994; Page 12; "New Hi/Low Switch Is Now Used On Certain Air Conditioned Machines".
Additional effective Product Identification Numbers (PIN's) should be added to the chart for the 114-5333 and 114-5334 Pressure Switches.
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Reference: Service Manual, Air Conditioning And Heating Systems With R-134a Refrigerant, SENR5664-01.
Description of Change: A new air conditioner hi/low refrigerant pressure switch is now used. The switch is connected in series with the compressor clutch coil to prevent compressor operation when the refrigerant pressure is too high or too low.
The new switch has a reduced "low" setpoint to enable the air conditioner compressor to operate at lower ambient temperatures. This allows customers to defrost or defog operators compartments in early morning, or cool operators compartments when the ambient temperature is low but heat load from the sun is high. The new setpoint provides open contacts below 170 kpa (25 psi) and closed contacts between 170 kpa (25 psi) and 275 kpa (40 psi) on pressure rise. On pressure fall, the contacts will open between 275 kpa (40 psi) and 170 kpa (25 psi), and stay open below 170 kpa (25 psi). The high pressure setpoint has not changed. Also, the new switch has a high current contact while some of the former switches had a low current contact.
If the machine has a Sanden compressor, the hi/low pressure switch is mounted into a special fitting on the rear of the air conditioner compressor. If the machine has a Harrison compressor, the hi/lo pressure switch is mounted in a port located on the discharge side block fitting.
Adaptable To: The new 114-5333 and 114-5334 Pressure Switches are in effect with the machines shown in the chart. The 114-5333 Pressure Switch has a 2-pin Deutch® DT connector and is a direct replacement for the former 3E-6043 Pressure Switch. The new 114-5334 Pressure Switch, has a 2-pin Sure-Seal® connector, is a direct replacement for the former 103-8530 Pressure Switch. Both of the former switches are no longer serviced.
