Friedrich Kuhl KCS12B10A Service Manual page 59

Cool with Heat Units
COMPLAINT
Room temperature uneven
(Heating cycle)
Does not heat adequately
Unit cools when heat is called
for
Cooling adequate, but heating
insufficient.
59
TROUBLESHOOTING
CAUSE
Bad indoor ambient thermistor
Fan speed too low
Exhaust or fresh air door open
Dirty filter
Unit undersized
Heater hi-limit control cycling on & off
Shorted or open supplementary heater
Incorrect wiring
Incorrect wiring
Defective solenoid coil
Reversing valve fails to shift
Reversing valve failing to shift
completely; bypassing hot gas
SOLUTION
Check diagnostic codes. Check Thermistors. Replace as
needed.
Set at higher fan speed.
Check if operating properly. Instruct customer on proper use
of control
Clean (See Routine Maintenance)
Check heat rise across coil. If unit operates efficiently, check
if insulation can be added to attic or walls. If insulation is
adequate, recommend additional unit or larger one
Check for adequate fan air across heater. Check for open hi-
limit control.
Do ohmmeter check.
Check applicable wiring diagram
Refer to applicable wiring diagram
Check for continuity of coil
Block condenser coil & switch unit to cooling. Allow pressure
to build up in system, then switch to heating. If valve fails to
shift, replace valve.
De-energize solenoid coil, raise head pressure, energize
solenoid to break loose. If valve fails to make complete shift,
replace valve.