Operating instructions

TM 11574A-OI
3-64
u. No evaporator air flow or restricted air flow.
(1) Evaporator coil blocked.
Step Probable Cause Remedy
1 Frost on coil. Refer to section 3-11d.
If fault is not corrected proceed to step 2.
2 Dirty coil. Refer to section 3-10b(11).
If fault is not corrected proceed to step j(2).
(2) No or partial evaporator air flow.
Step Probable Cause Remedy
1 Evaporator fan motor internal protector open. Refer to section 3-10b(12).
If fault is not corrected proceed to step 2.
2 Evaporator motor(s) defective. Refer to section 3-10b(12).
If fault is not corrected proceed to step 3.
3 Evaporator fan(s) loose or defective. Refer to section 3-10b(12).
If fault is not corrected proceed to step 4.
4 Evaporator fan motor contactor defective. Replace evaporator fan motor contactor
IAW 3-10b(11)(b)
v. Thermostatic expansion valve malfunction.
(1) Low suction pressure with high superheat.
Step Probable Cause Remedy
1 Low refrigerant charge. Check refrigerant IAW 3-10b(2)(e).
Recharge refrigerant IAW 3-10b(4).
If fault is not corrected proceed to step 2.
2 External equalizer line plugged. Open external equalizer line IAW
3-b10(10)(e).
If fault is not corrected proceed to step 3.
3 Wax, oil or dirt plugging valve or orifice ice
formation at valve seat.
Refer to section 3-10b(10).
If fault is not corrected proceed to step 4.
4 Superheat too high. Refer to section 3-10b(10).
If fault is not corrected proceed to step 5.