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CONTINUOUS BLOWER MODE

When the R to G circuit is closed by the thermostat, the blower

motor BLWM will operate on continuous-blower speed (can be

set to LO HT, HI HT, or COOL speed). Factory default is LO HT

speed. Terminal EAC-1 is energized as long as the blower motor

BLWM is energized.
During a call for heat, the blower BLWM will stop during igniter

warm-up (17 seconds), ignition (7 seconds), and blower-ON

delay (66 seconds), allowing the furnace heat exchangers to heat

up more quickly, then restarts at the end of the blower-ON delay

period at LO HT or HI HT speed respectively.
In high-heat, the furnace control CPU will hold the blower motor

BLWM at HI HT speed during the selected blower-OFF delay

period before reverting to continuous-blower speed.
When the thermostat “calls for low-cooling”, the blower motor

BLWM will switch to operate at low-cool speed (same speed as

LO HT). When the thermostat is satisfied, the blower motor

BLWM will operate an additional 90 seconds on low-cool speed

before reverting back to continuous-blower speed.
When the thermostat “calls for high-cooling”, the blower motor

BLWM will operate at COOL speed. When the thermostat is

satisfied, the blower motor BLWM will operate an additional 90

seconds

COOL

speed

before

reverting

back

continuous-blower speed.
When the R to G circuit is opened, the blower motor BLWM will

continue operating for an additional 5 seconds, if no other

function requires blower motor BLWM operation.

Continuous Blower Speed Selection from Thermostat

-- To

select different continuous-blower speeds from the room

thermostat, momentarily turn off the FAN switch or push-button

on the room thermostat for 1 -- 3 seconds after the blower motor

BLWM is operating. The furnace control CPU will shift the

continuous- blower speed from the factory setting of LO HT to

HI HT speed. Momentarily turning off the FAN switch again at

the thermostat will shift the continuous-blower speed from HI HT

COOL.

Repeating

the

procedure

will

shift

the

continuous-blower speed from COOL to LO HT speed. The

selection can be changed as many times as desired and is stored

in the memory to be automatically used following a power

interruption.

HEAT PUMP

(See Fig. 52, 53, 54 and 55 for thermostat connections)
When installed with a heat pump, the furnace control

automatically changes the timing sequence to avoid long blower

off times during demand defrost cycles. When the R to

W/W1-and-Y1 or R to W/W1-and-Y1-and-G circuits are

energized, the furnace control CPU will switch to or turn on the

blower motor BLWM at low cool speed (same speed as LO HT),

and begin a low-heat cycle. The blower motor BLWM will

remain on until the end of the prepurge period, then shut off for

24 seconds then come back on at LO HEAT speed. When the

W/W1 input signal disappears, the furnace control begins a

normal inducer post-purge period and the blower remains running

at LO HT speed. If the R-to-W/W1-and-Y1-and-G signals

disappear at the same time, the blower motor BLWM will remain

on for the selected blower-OFF delay period. If the R-to

W/W1-and-Y1 signals disappear, leaving the G signal, the blower

motor BLWM will remain on for the selected blower-OFF

delay period then switch to continuous-blower speed.
When the R-to W/W1-and-Y/Y2, R-to-W/W1-and-Y/Y2-

and-G,

R-to

W/W1-and-Y1-and-Y/Y2,

R-to-W/

W1-and-Y1-and- Y/Y2-and-G circuits are energized the

furnace control CPU will switch to or turn on the blower motor

BLWM at COOL speed, and begin a high-heat cycle. The

blower motor BLWM will remain on until the end of the

prepurge period, then shut off for 24 seconds then come back

on at HI HT speed. When the W/W1 input signal disappears,

the furnace control begins a normal inducer post-purge period

and the blower switches to COOL speed after a 3 second delay.

the

R-to-W/W1-and-Y/Y2-and-G

R-to

W/W1-and-Y1-and- Y/Y2-and-G signals disappear at the same

time, the blower motor BLWM will remain on for the selected

blower-OFF delay period. If the R-to W/W1-and-Y/Y2 or

R-to-W/W1-and-Y1-and-Y/Y2 signals disappear, leaving the G

signal, the blower motor BLWM will remain on for the selected

blower- OFF delay period then switch to continuous-

blower speed.

COMPONENT SELF-TEST

NOTE

The furnace control component test allows all

components to run for a short time; except the gas valve and
humidifier terminal HUM are not energized for safety reasons.
The EAC-1 terminal is energized when blower is energized. This
feature helps diagnose a system problem in case of a component
failure. The component test feature will not operate if any
thermostat signal is present at control and not until all time delays
are completed.
To Begin Component Self-Test:

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal injury,

or death.
Blower access panel door switch opens 115-v power to control

board. No component operation can occur. Caution must be

taken when manually closing this switch for service purposes.

WARNING

1. Remove blower access door.
2. Disconnect thermostat R lead from furnace control.
3. Manually close blower door switch.
4. For approximately 2 sec, short (jumper) the C

-24v

terminal on control to the TEST/TWIN 3/16-in. quick-

connect terminal on control until LED turns off. Remove

jumper from terminals. (See Fig. 37.)

NOTE

: If TEST/TWIN and C

-24v terminals are jumpered

longer than 2 sec, LED will flash rapidly and ignore component
test request.
Component test sequence for 2-stage furnace is as follows:

a. LED will display previous status code 4 times.

b. Inducer motor starts on high-speed and continues to

run until Step g of component test sequence.

c. Hot surface igniter is energized for 15 sec, then off.