Service Guide
SERVICING
31
thermostat. During the “OFF” cycle it heats the bimetal
element helping the thermostat call for the next cooling cycle.
This prevents the room temperature from rising too high
before the system is restarted. A properly sized anticipator
should maintain room temperature within 1 1/2 to 2 degrees.
The anticipator is xed in the subbase and is not to be
replaced. If the anticipator should fail for any reason, the
subbase must be changed.
As more and more electronic’s are introduced to the Heating
Trade, Polarization of incoming power and phasing of pri-
mary to secondary voltage on transformers becomes more
important.
Polarization has been apparent in the Appliance industry
since the introduction of the three prong plug, however, the
Heating Industry does not use a plug for incoming power,
but is hard wired.
Some of the electronic boards being used today, with ame
rectication, will not function properly and/or at all without
polarization of incoming power. Some also require phasing
between the primary and secondary sides of step-down
transformers.
A step-down transformer 120 volt primary to 24 volt secondary,
40 VA (Heating and Cooling Models) supplies ample capacity
of power for either operation.
S
R R SR R
R R
R
SRS RS
R S S
RR RS JR R
1. Remove blower compartment door to gain access to
the thermostat low voltage wires located at the furnace
integrated control module.
2. Remove the thermostat low voltage wires at the furnace
integrated control module terminals.
With Power On (and Door Interlock Switch closed):
RS
3. Use a voltmeter, check voltage across terminals R and
C. Must read 24 VAC.
4. No voltage indicates faulty transformer, open fuse, bad
wiring, bad splice, or open door interlock switch.
5. Check transformer primary voltage at incoming line
voltage connections, fuse, splices, and blower door in-
terlock switch.
6. If line voltage is available to the primary side of trans-
former and not at secondary side, the transformer is
inoperative. Replace.
7. After completing check and/or replacement of trans-
former and check and/or repair of control circuit, rein-
stall blower compartment door.
8. Turn on electrical power and verify proper unit opera-
tion.
S
R R SR
1. Remove blower compartment door to gain access to the
circulator blower motor and integrated ignition control.
2. Check for any obstruction that would keep the fan wheel
/ fan motor from turning.
3. Check wiring, the motor has two wiring harnesses, a main
harness and a control harness. The main pin harness has:
White neutral wire connected to the Neutral terminal on
the control board. Black wire connected to the CIRC H
terminal on the control board. Red wire connected to the
COM terminal, which is a female spade connection next
to the T1 – T4 wires on the control board.
Green ground wire connected to cabinet ground .
The control harness has:
Blue wire connected to T1 on the control board.
Red wire connected to T2 on the control board.
Orange wire connected to T3 on the control board.
Black wire connected to T4 on the control board.
The multi-speed ECM motor requires a line voltage power
supply (black connected to CIRC H and white connected
to neutral on the control board) as well as a signal on one
of the speed taps (T1-T4).
The speed tap voltage is A.C. and can vary which tap is
energized depending on DIP switch selection. The voltage
reading from any one of the speed taps is referenced
between the female COM terminal next to the speed taps
on the control board. From COM to T1 or T2, T3, T4, you
should read 24 VAC on the low voltage speed taps.
CONNECTOR ID DESCRIPTION CONNECTOR VOLTAGE
L LINE, L1 LINE, L1
G GROUND CHASSIS GROUND
N LINE, L2 LINE, L2
C SIGNAL COMMON 24VAC COMMON
1 TAP 1 24VAC
2 TAP 2 24VAC
3 TAP 3 24VAC
4 TAP 4 24VAC
5 TAP 5 24VAC
Motor Tap Identification