TM 9-2320-361-20 Table 2-4. Electrical Troubleshooting (Contd). MALFUNCTION TEST OR INSPECTION CORRECTIVE ACTION END OF TESTING! 37. LOW AIR PRESSURE WARNING SYSTEM DOES NOT COME ON BELOW 60 PSI AND DOES NOT GO OFF ABOVE 66 PSI Test low air pressure switch operation. Air pressure switch should open and close between 54 and 66 psi. Step 1. Step 2. Step 3. Step 4. Step 5. Turn accessory/ignition switch to OFF position. Turn air reservoir draincock to left and drain reservoir (TM 9-2320-361-10) to less than 54 psi. Close draincock. Turn accessory/ignition switch to ON position. Buzzer should operate. Start engine (TM 9-2320-361-10) and allow air pressure to buildup in air reservoir. Warning buzzer should turn off at 66 psi and above. If air pressure switch fails either test in step 3 or 4, replace air pressure switch (para. 4-25). END OF TESTING! 2-133