IM 950-1 / Page 35 of 38
Troubleshooting
These items should be checked by a qualified service technician only.
Trouble
Cause
Cure
1. Blowers won’t operate on cool
2. Blowers operate on cool but compressor
does not start
3. Blowers run on cool and compressor starts but stops
after a short interval.
.
Blowers run on cool and compressor starts and runs, but
compressor occasionally stops (on overload device).
5.
Compressor starts and runs on cool but
blowers do not run.
6. Compressor starts and runs on cool, but fan motor starts,
then stops.
7. Equipment gives electrical shock.
8. Insufficient cooling capacity.
a.
No power
b. Faulty touchpad/thermostat.
c. Loose connections at push-button switch.
a. Thermostat set too high.
b. Heat valve is open and heat is on.
c. Low voltage.
d. Faulty touchpad/thermostat.
e. Faulty connection at touchpad/thermostat
f.
Defective wiring to thermostat.
g. Loose connections at compressor terminals.
h. Wiring to compressor terminals defective.
i.
Loose connections in compressor overload device.
j. Starting capacitor malfunctions (open circuited, short
circuited or loss of capacity).
k. Defective compressor motor (short circuited, open
circuited, grounded).
a. Operation of overload device due to overloading com
-
pressor motor.
a. Low voltage due to overload circuits within building or
throughout the local power system. Due to varying power
demands, this condition might exist only at certain times
during the day or on very hot days.
b. High voltage due to fluctuations in local power system;
usually occurs during low load periods of the day
c. Partial short circuit in compressor motor. Under normal
loading a compressor with a partial short circuit might
appear to be operating all right; increased condensing
air temperature might then cause a short.
a. Faulty touchpad/thermostat.
b. Open circuited blower motor.
c. Blower rubbing against its housing.
d. Bearings on blower motor seized.
e. Loose connection at touchpad/thermostat.
a. Operation of the internally connected overload device
due to a short circuit in blower motor.
b.
Windings, rubbing of blower wheel or lack of lubrication
in blower motor bearings.
a. Grounded electrical circuit.
a. Equipment standing too long without being run.
b. Insufficient airflow through condenser due to:
1) Dirty condenser.
2) 0bstructed louver on outer cabinet or wall box.
3) Condenser blower/fan not running.
4) Condenser blower/fan not up to speed.
5) Condenser blower/fan slipping on motor shaft.
6) Recirculation of condenser air.
c. Insufficient airflow through evaporator due to:
1) Dirty evaporator.
2) Ice on evaporator coils.
3) Dirty air filter.
4) Obstructed discharge grilles.
5) Evaporator blower motor not running.
6) Evaporator blower motor not up to speed.
7) Evaporator motor slipping on motor shaft.
d. Heat load in room exceeds capacity of equipment.
e. Windows and doors in room are open
f.
Compressor not pumping, indicated by:
1) Low wattage.
2) Condenser not warm, evaporator only
partially cool or not at all .
g. Restricted capillary or strainer.
1 ) Frost on capillary or strainer
2) Low wattage.
3) Condenser not warm.
4) Evaporator partially frosted, only partially cool
or not at all.
a. Check supply line fusses, circuit breakers, and be sure
the power is on. Blown fuses would indicate circuit over-
loading, a short circuit, or a ground condition in the circuit
Voltage supply to the equipment should be checked.
Voltage underload must be within 10% of voltage given
on date plate.
b. Replace.
c
Tighten.
a. Adjust Rotate control knob to “Cooler.”
b. Close heat valve.
c. Check as above.
d. Replace.
e. Tighten.
f.
Replace.
g. Tighten.
h.
Replace.
i.
Tighten.
j. Replace.
k. * Ship cooling chassis prepaid to nearest McQuay au-
thorized warranty station.
a. Check voltage supply. Clean condenser inside and out.
Check at outside face of condenser for recirculation of
condenser air. Put air “splitters” in, if missing. Check com-
pressor for short circuit. If defective, ship cooling chassis
to nearest McOuay authorized warranty station.
a. Run separate electric line to equipment Consult local
power company.
b.
Consult local power company.
c. If confirmed, ship cooling chassis prepaid to nearest
McOuay authorized warranty station.
a. Replace.
b. Replace.
c.
Adjust blower motor or blower wheel position.
d. Replace motor
e. Tighten.
a. Replace motor
b. Adjust blower wheel or motor, or replace.
a.
Eliminate ground.
a. If the air conditioner is allowed to stand for an extended
length of time without being run on cool, it is possible for
all the refrigerant to become absorbed in the oil inside the
compressor and refrigeration circuit. If this should hap-
pen there will be no cooling until the necessary working
pressures have been established. This will take about 5
minutes of continuous running.
b.
1) Clean.
2) Remove obstructions.
3) Check same as in the case of malfunctioning
condenser air blower.
4) Check for correct voltage. Replace blower motor
if necessary
5) Adjust blower position and tighten setscrews.
6) Correct as in No 3 above.
c.
1) Clean.
2) Turn equipment off to let ice melt (see last
two items of No. 9 “Too much cooling,” on page 37.
3) Clean or replace.
4) Remove obstructions.
5) Check as in No. 1.
6) Check for correct voltage.
Replace motor if necessary.
7) Adjust blower wheel position and tighten setscrew
d. Refer to original load calculations, recalculate heat load.
e. Close them.
f.
* Ship prepaid to nearest McQuay warranty
station.
g. * Ship prepaid to nearest McOuay warranty
station.
