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Using a Manifold Gauge Set
When using a manifold gauge set to diagnose, recharge, or service the tractor air conditioning system:
1. Be sure that all equipment hose lines are fitted with shutoff valves or check valves within 30 cm (12 in) of their
ends and that the valves are closed. This will ensure that only minimal quantities of refrigerants escape to the
atmosphere, and that only small amounts of moisture and other contaminants can enter the system.
2. Be sure that all equipment including the connecting hose lines and manifolds are:
- Compatible with the refrigerant in the air conditioning system;
- Free of all contaminants;
- Used only for the same type of refrigerant in the system.
3. Be certain that all shutoff valves are closed tightly before connecting them to the air conditioning system or charging
source.
4. Connect the manifold gauge set to the unit according to the instructions supplied by the gauge manufacturer.
5. Perform the desired diagnostic and service operation.
6. Close the shutoff valves on the service hoses.
7. Disconnect the hoses from the system.
NOTE: Attach the hoses to recovery or recycling equipment whenever disconnecting the manifold gauge set from
the air conditioning system, emptying refrigerant from it, or moving the center hose to another device which cannot
accept refrigerant pressure. Remove the refrigerant, lubricant, and contaminants from the hoses.
Checking Refrigerant for Excess Air
At times you may question whether or not a container of refrigerant has been recycled. One check which can be done
in the shop is to determine if there is excess air mixed in with the refrigerant. This check is a simple comparison of
the container pressure with theoretical pressure at a known temperature. If the pressure is equal to or less than a
theoretical value of usable purity established for R134
NOTICE: Using R134
with excess air will result in higher system operating pressures and may cause damage to the
A
air conditioning system.
Do this check in the following manner:
1. Store the container for at least 12 hours at a known temperature of 18.3 °C (65 °F) or higher. The container must
not be in direct sunlight or under the influence of any other direct source of heat.
Carry out all of the next steps in the same area in which the container is stored, as it is very important that the
temperature of the container remain stable.
2. Attach an appropriate pressure gauge to the container. This pressure gauge should read in increments of 6.9 kPa
(1 psi)
3. Use a calibrated thermometer to measure the air temperature within 10 cm (4 in) of the container surface.
4. Compare the pressure in the container with the pressure shown for the temperature of the tank for R134
pressure in the container is equal to or less than the pressure in the table, the refrigerant in the container meets
the requirements for excess air.
If the pressure is greater than shown in the table, you may still be able to use the refrigerant by proceeding to step
5.
5. If the pressure exceeds that of the table, connect the tank to recovery or recycling equipment in such a way as to
allow you to continue to monitor tank pressure.
6. Bleed a small amount of vapor from the tank into the recovery or recycling equipment until the tank pressure is
below that shown in the table for the temperature at which the tank was stored. Close the shutoff valves in the
recovery/recycling equipment service hose.
NOTICE: This process may cause the temperature of the tank to drop.
7. Allow the tank temperature to stabilize at the temperature of the storage room by shaking it and allowing it to sit in
the same spot for up to another 12 hours.
INTRODUCTION
, the container does not have excess air.
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. If the
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