AIR CONDITIONING (Cont) - TM-55-1905-223-24-170217

TM 55-1905-223-24-17

Table 4-1. Troubleshooting - CONT

Malfunction

Test or Inspection

Corrective Action

AIR CONDITIONING - CONT

11.

Compressor motor hums but does not start.

STEP 1.

Check to see if compressor motor is defective. Replace if "short" or "open" in windings

12.

Compressor short cycles on high pressure cut-out.

STEP 1.

Check to see if compressor discharge stop service valve is partially closed (A/C-2;

accommodations). Turn valve fully (counterclockwise).

STEP 2.

Check to see if high (discharge) pressure control (solenoid) is defective. Check for

defective control. Replace as required (paragraph 4-14).

STEP 3.

Check for air or non-condensables in system. Purge, (Malfunction 4). If purging is not

successful, remove charge, evacuate, and recharge system with R-22 (paragraph 4-10).

13.

Compressor short cycles on low pressure cut-out.

STEP 1.

Check for shortage of refrigerant. Find and repair leak. Evacuate and recharge system

with R-22 (Malfunction 10 and paragraph 4-10).

STEP 2.

Check to see if suction stop (service) valve is partially closed (A/C-2; accommodations).

Turn valve fully counterclockwise.

STEP 3.

Check to see if suction strainer is clogged on semi-hermetic type compressor (A/C-2;

accommodations). Remove and clean debris from strainer (paragraph 4-9).

14.

Compressor runs continually.

STEP 1.

Check for shortage of refrigerant. Find and repair leak. Evacuate and recharge system

with R-22 (Malfunction 10 and paragraph 4-10

STEP 2.

Check to see if compressor discharge valve leaks (A/C-2; accommodations).

NOTE

A low discharge pressure (below 170 psig) combined with a high suction pressure

(above 72 psig) indicates a leaky valve plate.

4-10