Troubleshooting Guide

MRCOOL Universal Service Manual
54
(2) The following situations are not operation failures.
Problem
Time of occurrence
Cause
Mist comes from the air
conditioner.
During operation.
If the unit is running under high humidity,
the wet air in the room will be quickly
cooled down.
The air conditioner generates
some noise.
System switches to heating mode after
defrosting.
Defrosting process will generate some
water, which will turn to water vapor.
The air conditioner is buzzing at the
beginning of operation.
Thermostat will be buzzing when it starts
working. The noise will become weak 1min
later.
Dust comes from the air
conditioner.
When the unit is turned on, it purrs.
When the system is just started, the
refrigerant is not stable. About 30s later,
the purr of the unit becomes low.
About 20s after the unit first enables the
heating mode or there is refrigerant
brushing sound when defrosting under
heating.
It’s the sound of 4-way valve switching
direction. The sound will disappear after
the valve changes its direction.
There is hissing sound when the unit is
started or stopped and a slight hissing
sound during and after operation.
It’s the sound of gaseous refrigerant that
stops flowing and the sound of drainage
system.
There is a sound of crunching during and
after operation.
Because of temperature change, front
panel and other components may be
swelled up and cause abrasion sound.
There is a hissing sound when the unit is
turned on or suddenly stopped during
operation or after defrosting.
Because refrigerant suddenly stops flowing
or changes the flow direction.
The unit starts operation after being
unused for a long time.
Dust inside the units come out together
with the air.
The air conditioner generates
some smell.
During operation.
The room smell or the smell of cigarette
comes out through the units.
NOTICE:
Check the above items and adopt the corresponding corrective measures. If the air conditioner continues to
function poorly, please stop the air conditioner immediately and contact MRCOOL's authorized local service
center. Ask our professional service staff to check and repair the unit.