AC system pressure checks - TB-9-2320-279-13-10053

DRAFT

TB 9-2320-279-13-1

FIELD LEVEL TROUBLESHOOTING INTRODUCTION - Continued

(e) The AC condenser receiver/dryer is normally at outside temperature. If the AC condenser receiver/

dryer is cool or cool spots form, a blockage has formed in the AC condenser receiver/dryer.

(f) A blockage at the inlet of the AC condenser receiver/dryer will cause high system high-side

pressure.

(g) A blockage at the outlet of the AC condenser receiver/dryer will cause low system high-side

pressure and little or no cooling.

(h) If the AC expansion valve is stuck closed, the AC expansion valve and AC evaporator core will be at

outside temperature.

(i) If the AC expansion valve is stuck open, the AC expansion valve and AC evaporator core will be

extremely cold and frost or ice buildup may occur.

(j) If ice is forming in the AC expansion valve, the system may stop cooling when the ice forms, and

start cooling when the expansion valve warms up enough to melt the ice, causing the system to

appear to cycle ON and OFF.

(k) A blockage in the AC evaporator core will cause low system low-side pressure and little or no

cooling.

(l) A leak in the AC evaporator core or AC expansion valve fittings may not be detectable with leak

detector.

(m) A restriction in a low system side AC hose will cause low system low-side pressure and little or no

cooling. Cool spots and frost may form at location of restriction.

(n) A restriction in a high system side AC hose will cause high system high-side and low system low-

side pressure and insufficient cooling. Cool spots and frost may form at location of restriction.

6. AC system pressure checks. In addition to the performance checks noted above, the troubleshooting

procedures for the HEMTT AC system will also include system pressure checks, using standard AC test

set recovery/recycling manifold gages. Before using the manifold gages to measure AC system

pressure, ensure that the system is fully charged and stabilize the system by ensuring that all cab

windows and vents are closed, personnel heater is OFF, and by running the system at high heater/

evaporator blower speed for 5 to 10 minutes.

d. Wire Repair.

Refer to TM 9-2320-279-20 for the repair of wire harness connectors. Wire harness repair

is limited to splicing and taping of wires at Field Level Maintenance. If a wire harness cannot be repaired, notify

Supervisor.

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