290699-YIM-B-0607
54
Unitary Products Group
On calls for heating, the supply air blower operates but
the draft motor does not (the room thermostat fan
switch is in the “AUTO” position).
1.
The draft motor has inherent protection. If the
motor shell is hot to the touch, wait for the internal
overload to reset.
2.
If the motor shell is cold with the room thermostat
calling for heat, check if 24 volts is present at the
room thermostat but not at the UCB, check for
proper wiring between the thermostat and the
UCB, i.e. that the thermostat “W1” terminal is con-
nected to the “W1” terminal of the UCB, and for
loose wiring.
3.
The draft motor is a 230 volt draft motor on all mod-
els regardless of unit supply voltage. If the ICB is
flashing a code other than the heartbeat, then trou-
bleshoot the device indicated by the fault code. If
not, then remove power to the unit for more than
20 seconds. If upon restoring the power to the unit
the draft motor does not start with a call for heat,
then verify that terminal “L1” of the ICB has a mini-
mum of 120 volts to ground on 230 and 460 volt
models or a minimum of 18 volts to ground on 575
volt models. If terminal “L1” does not have the min-
imum voltage, then check the wiring between the
unit control box and the ICB on all models and on
460 volt models, the transformer in the gas heat
compartment and its wiring. If terminal “L1” does
have the minimum voltage, then check for the min-
imum voltage on terminal “IND” of the ICB on sin-
gle stage models and terminal “IND HIGH” of the
ICB on two stage models. If voltage is not present
at the terminal, then verify wiring between the con-
trol box and the ICB. If all wiring is intact, then ICB
is at fault. If voltage is present at the terminal on
230 and 460 volt models, then the draft motor is at
fault. On 575 volt models, if voltage is present at
the terminal, then check the draft motor relay DMR
mounted above the ICB. First verify that the relay is
pulled in by visual inspection. If not, then verify the
minimum voltage is present between terminals “A”
and “B” of the relay. If the minimum voltage is not
present, then check the wiring. If it is present, then
verify that a minimum of 150 volts is present at ter-
minals “5” and “7” of the draft motor relay. If not
present at terminal “7” of the draft motor relay, then
troubleshoot the transformer in blower section and
its wiring. If present at terminal “7” and not at termi-
nal “5” of the draft motor relay, then the relay is at
fault. If the minimum voltage is present at terminal
5 of the draft motor relay, then the draft motor is at
fault.
The ignitor sparks at the pilot burner but the pilot does
not ignite and a gas odor is detected at the draft motor
outlet.
1.
Adjust the pilot adjust screw on the gas valve as
described in “PILOT CHECKOUT” on page 47.
2.
Check the supply pressure as described in “POST
START CHECK LIST” on page 46. Make adjust-
ments as necessary.
3.
Check the pilot orifice and pilot burner for obstruction
as described in paragraph above. Clean as needed
but the problem should not be the gas valve.
The pilot burner ignites but the ignitor continues to
spark and the main burners do not ignite.
1.
Make the same checks and adjustment as
described in “PILOT CHECKOUT” on page 47.
2.
Check the supply pressure as described in “POST
START CHECK LIST” on page 46. Make adjust-
ments as necessary.
3.
Make sure that the pilot burner is not bent or dam-
aged.
4.
Make sure that the ground connections at the pilot
burner, gas valve and ignition control are intact.
Check the ignitor wire for good electrical connec-
tion. If all are intact, replace the ignition control.
The pilot burner lights and the spark stops but the main
burners do not light.
1.
Check electrical connections between the ignition
control and the gas valve. If intact, check for 24
volts across terminals “MV” and “GROUND” termi-
nals. If no voltage detected, replace ignition con-
trol. If voltage is present, replace gas valve.
Main burners light but exhibit erratic flame characteristics.
1.
Adjust air shutters as described in “BURNER AIR
SHUTTER ADJUSTMENT” on page 47.
2.
Check the main burner orifices for obstruction and
alignment. Removal procedure is described in
BURNER INSTRUCTIONS on page 47. Clean or
replace burner orifices and burners as needed.
UNIT FLASH CODES
Various flash codes are utilized by the unit control
board (UCB) and the ignition control board (ICB) to aid
in troubleshooting. Flash codes are distinguished by
the short on and off cycle used (approximately 200ms
on and 200ms off). To show normal operation, the con-
trol boards flashes a 1 second on, 1 second off “heart-
beat” during normal operation. This is to verify that the
