10 
 
B. The Thermostat (temperature control) –In the 
cooling mode, the thermostat regulates the “ON” 
and  “OFF”  temperature  setting  at  which the 
compressor will operate. 
For  “Heat/Cool”  models,  the  thermostat  also 
controls the “ON” and “OFF” temperature settings 
of the heater assembly (See Figure 1). 
C. Louvers –The louvers are located at both ends 
of the ceiling assembly and are used in directing 
the discharge air from the unit. 
iii. OPERATION 
I. For Cooling (Refer to Figure 1, page 9). 
A. Turn the selector switch to the “LOW COOL” or 
“HIGH COOL” position. 
B. Rotate the thermostat (temperature control) to the 
position that is the most comfortable to you. The 
thermostat will turn the compressor on when the 
temperature of the air entering the heat pump 
rises a few degrees above the setting you have 
selected. When the temperature of the air 
entering the heat pump drops below the selected 
setting, the thermostat will turn the compressor 
off. The Heat pump, while in the cooling mode, 
will continue to cycle the compressor on and off 
in the above-mentioned fashion until the selector 
switch is turned to another mode of operation. 
C. Position the louvers to the desired direction the 
discharge air is to flow. 
NOTE: The fan operation is constant, only the 
compressor cycles on the thermostat. 
II. Operation During Cooler Nights (Cooling 
Operation) 
It is important when the outdoor temperature drops 
in the evening or during the night to below 75°F, that 
the thermostat (temperature control) be set at a 
midpoint  between  “Warmer”  and  “Cooler”.  If  the 
setting  is  at  “Cooler”,  the  evaporator  coil  may 
become iced-up and stop cooling. During the day 
when the temperatures have risen above 75°F, reset 
the thermostat switch to the desired setting. 
NOTE: Should icing-up occur, it is necessary to let the 
cooling (evaporator) coil defrost before normal cooling 
operation is resumed. During this time, operate the 
unit  in  the  “HIGH  FAN”  position with the system at 
maximum air flow. When increased or full air flow is 
observed, the cooling coil should be clear of ice. 
 III. Short Cycling 
When a heat pump is in operation, its compressor 
circulates refrigerant under high pressure. Once off, it 
will take two to three minutes for this high pressure to 
equalize. The air conditioning compressor is unable to 
start against high pressure. Therefore, once the heat 
pump is turned off, it is important to leave it off for two 
to three minutes before restarting. 
Short cycling the compressor (or starting it before 
pressures have equalized), will in some instances, 
kick the circuit breaker or overload. 
IV. For Heating Operation (Refer to Figure 1, page 9). 
NOTE: The heat pump will operate on reverse cycle 
refrigerant heating at outdoor temperatures above 
freezing. When the outdoor temperature is below 
freezing, the heat pump compressor will shut down to 
prevent outdoor coil freeze-up. At this time, if the 
optional auxiliary electric resistance heater has been 
installed, it will be energized to take the chill out of the 
indoor air. The electric resistance heater is not a 
substitute for a furnace at these low outdoor 
temperatures. 
A. Turn  the  selector  switch  to  the  “HIGH  HEAT” 
position. At “HIGH HEAT”, the fan operates on high 
speed with heat output at maximum. 
B. Rotate the thermostat (temperature control) switch 
to the position that is the most comfortable to you. 
The thermostat will turn the compressor/heater on 
when the temperature of the air entering the heat 
pump unit drops below this setting a few degrees 
and automatically turns off when the temperature 
of the air entering the heat pump rises a few 
degrees above this setting. The compressor/heater 
will continue to cycle on and off in this fashion until 
the selector switch is turned to another mode of 
operation. 
C. Position the louvers to the desired direction the 
discharge air is to flow. 
Discharge air temperature can be controlled to 
some extent by opening or closing the louvers. 
When the louvers are closed, the warmest localized 
discharge air is achieved. Fully opened louvers will 
throw the warm discharge air to the back and front 
of the vehicle for more efficient circulation and 
faster warm-up. Although the air temperature is 
lower with the louvers fully opened, the heating 
capacity is still the same. 
V. For Air Circulation Only (Refer to Figure 1, page 8). 
A. Turn  the selector  switch to  “LOW  FAN”  or for 
maximum air flow, to “HIGH FAN”. 
B. Position the louvers to the desired direction the 
discharge air is to flow. 
NOTE: When  the  selector  switch  is  in  the  “LOW 
FAN” or “HIGH FAN” position, the blower motor will 
operate continuously. 
v. ROUTINE MAINTENANCE 
I. Owner –One of the biggest advantages to your new 
Coleman-Mach Heat pump is that the maintenance 
needed to keep the unit in good working order is 
minimal. In fact, about the only thing you, the owner, 
must take care of is the cleaning and replacement of 
the filters. 
Filters are made from long life non-allergenic natural 
fibers which can be cleaned and reused, and which 
completely filter the circulated air when the heat pump 
is in operation. If the filters are not cleaned at regular 
intervals, they may become partially clogged with lint, 
dirt, grease, etc. A clogged filter will produce a loss of 
air volume and may eventually cause an icing-up of 
the cooling (evaporator) coil. 
The ceiling assembly and the outside shroud can be 
cleaned with a damp cloth. When required, a mild 
detergent can be used. 
IMPORTANT 
Do not operate your heat pump for extended 
periods of time without the filter installed. 
An even more serious condition occurs when the 
heat pump is operated without a filter. When this 
happens, the lint, grease, etc. that are normally 
stopped by the filter are now accumulating in the 
cooling coil. This not only leads to a loss of air 
volume and a possible icing-up of the cooling coil 
but could also result in serious damage to the 
operating components of the heat pump. 
We recommend that the filters be cleaned and 
changed at least every two weeks when the heat 
pump is in operation.