Table 2-1. Direct Support Troubleshooting Guide (Continued)
TEST OR INSPECTION
(c) Replace the switch if it cannot be adjusted (para. 2-27).
(d) If the switch is actuating correctly, check the accuracy of the gauge which led to this malfunction
19. Air compressor pressure switch does not work. (Ref. Schematic diagram FO-1, sheet 8, schematic line 824).
This switch is set to open at about 1775 psig. It stays open until pressure drops to about
1550 psig and then recloses.
Step 1. Remove connectors P12 (REF: Interconnection diagram FO-2, Sheet 15) and P11 (REF: Interconnection
diagram FO-2, Sheet 14) from the control panel. Check for 110-120 VAC across J11B and J12J (REF:
Interconnection diagram FO-2, Sheet 9). The compressor switch, SS5(REF: Interconnection diagram FO-2,
Sheet 11) must be on.
If voltage is not present, go to step 6.
Step 2. Check for continuity across P11B and P11C.
Bleed off air pressure until it is less than 1400 psig before testing.
If there is continuity across P11B and P11C, go to step 6.
Step 3. Remove connector P24(REF: Interconnection diagram FO-2, Sheet 14) from the switch panel. Check for
continuity across J24B and J24C.
If there is continuity, replace/repair the cable between P11 and P24(para. 2-28).
Step 4. Refer to the electrical schematic Appendix E-1. Check continuity, point-to-point, from J24A to J24C.
(a) Repair any loose or damaged wires (para. 2-28).
(b) Replace/repair connector P24 if faulty (para. 2-28).
(c) Replace PSH7 (REF: Interconnection diagram FO-2, Sheet 14), if it shows an open circuit (para. 2-27).
Step 5. Open the cover PSH7 and insert a non-metallic tool into the switch arm. Press lightly until the switch transfers
to the open position. Check that continuity is broken between J24B and J24C.
If the switch does not open, replace PSH7 (para. 2-27).
Step 6. Refer to air compressor wont start control circuit troubleshooting for further troubleshooting steps.
20. Air compressor is on at more than 1850 psig or, is not on at less than 1400 psig.
Relieve all system air pressure before opening any air tubing lines by opening a drain
valve on the air manifold.
Test product air compressor pressure switch (PSH7) (REF: Interconnection diagram FO-2, Sheet 14) for accuracy.
Disconnect P24 (REF: Interconnection diagram FO-2, Sheet 14) from the pressure switch panel. Disconnect the
pressure sensing line from the switch. Remove the cover on the switch and tag/remove the wires from the pressure
switch. Set a multimeter to the Ohms x 1 scale and attach the leads to the switch terminals that the wires were on.
Connect a dead-weight tester or another known calibrated pressure control device to the switch pressure (or inlet)
port. The multimeter should read zero resistance with no pressure on the inlet pressure port. Slowly apply pressure to
the switch. The switch should open on an increasing pressure of 1750 to 1800 psig. Slowly relieve the pressure. The
switch should close at 1500-1550 psig.
(a) Replace the switch if there is internal leakage (para. 2-27).
(b) Replace the switch if testing shows it is actuating outside of the above listed limits (para. 2-27).
(c) Refer to pressure gauge troubleshooting if the switch is actuating within the above listed limits.