SMB Air Conditioner
12 VDC Owner’s Manual 9/09
Page 8 of 13
Chapter 6 – Troubleshooting
Troubleshooting Guide
PROBLEM/SYMPTOM
LIKELY
CAUSE(S)
CORRECTION
The unit does not
operate.
1. Power supply problem.
2. Tripped breaker/disconnect.
3. Thermostat
1. Check voltage at power supply. Check wiring to
unit and external breakers or fuses.
2. Check circuit protection devices for continuity.
3. Setpoint may be too high if in cooling mode or too
low if in heating mode; check unit and reset.
Thermostat may be out of calibration or otherwise
defective. Also check for loose connection(s).
Blower runs but
compressor does not
start.
1. Power supply problem.
2. Thermostat
3. Safety switches are
tripping out unit.
4. Loose or defective
wires.
5. Compressor
6. Refrigerant leakage or
loss.
7. Control board
1. Check voltage at power supply. Voltage at unit
must be + 10% of rated nameplate voltage.
2. Check the thermostat and unit for loose wires.
Secure any loose connection. Check location of
sensor and make sure that it does not touch the
indoor coil. The sensor and/or thermostat should
be replaced if defective.
3. Check for water flow. Check refrigerant charge.
Check switches for loose wire connection, broken
or burned contacts.
4. Tug on wires to see if they will separate from their
connections. Replace terminals if they are loose
or weak.
5. Check for electrical shorts, ground and open
circuits. Replace compressor if defective. If
electrical checks are ok, install a start capacitor
and direct wire to see if the compressor will start.
If this fails, remove and replace the compressor.
6. Locate leak(s), reclaim, repair, evacuate and
recharge unit with refrigerant.
7. Verify that power is being provided from the
control board. Replace control board if it is
defective.
Compressor runs, but
blower will not run.
1. Blower motor capacitor
2. Blower motor.
3. Power supply problem.
4. Control board
1. Verify capacitance, check for electrical shorts and
ground. If defective, replace.
2. Check for electrical shorts, ground and open
circuits. Replace blower motor if it is defective.
3. Check voltage at power supply. Voltage at unit
must be + 10% of rated nameplate voltage.
4. Verify that power is being provided from the
control board. Replace control board if it is
defective.
