Goodman Mfg VC8 User Manual

34

The normal operational sequence in heating mode is as fol-
lows:

•

R and W1 (or R and W1/W2) thermostat contacts close,
initiating a call for heat.

•

Integrated control module performs safety circuit checks.

•

Induced draft blower is energized on high speed for a 15-
second prepurge.  Humidifier terminal is energized with
induced draft blower.

•

Induced draft blower steps to low speed following
prepurge.  Low stage pressure switch contacts are
closed.

•

Igniter warm up begins upon step to low speed and
presence of closed low stage pressure switch contacts.

Off 

x Normal condition 

x None 

x None 

x None 

1 Flash 

x Communications 

Failure 

x Communications 

Failure 

x  Depress Learn Button 
x  Verify that bus BIAS 

and TERM 
dipswitches are in the 
ON position. 

x Depress once 

quickly for a power-
up reset 

x  Depress and hold 

for 2 seconds for 
an out-of-box reset 

Red 

Communications 

LED 

2 Flashes 

x Out-of-box reset 

x  Control power up 
x Learn button 

depressed 

x None 

x None 

Off 

x No power 
x Communications 

error 

x  No power to furnace 
x Open fuse 
x Communications error 

x  Check fuses and 

circuit breakers; 
replace/reset 

x  Replace blown fuse 
x  Check for shorts in 

low voltage wiring in 
furnace/system 

x  Reset network by 

depressing learn 
button 

x  Check data 1/ data 2 

voltages 

x Turn power OFF 

prior to repair 

1 Steady 

Flash 

x  No network found 

x Broken/ disconnected 

data wire(s) 

x  Furnace is installed as 

a legacy/ traditional 
system 

x Check 

communications 
wiring (data 1/ data 2 
wires) 

x Check wire 

connections at 
terminal block 

x Verify furnace 

installation type 
(legacy/ traditional or 
communicating) 

x  Check data 1/ data 2 

voltages 

x Turn power OFF 

prior to repair 

x Verify wires at 

terminal blocks are 
securely twisted 
together prior to 
inserting into 
terminal block 

x  Verify data1 and 

data voltages as 
described above 

Rapid 

Flashing 

x Normal network 

traffic 

x  Control is “talking” on 

network as expected 

x None 

x None 

Green Receive 

LED 

On Solid 

x  Data 1/ Data 2 

miss-wire 

x  Data 1 and data 2 

wires reversed at 
furnace, thermostat, 
or CT™ compatible 
outdoor AC/HP 

x  Short between data 1 

and data 2 wires 

x  Short between data 1 

or data 2 wires and R 
(24VAC) or C (24VAC 
common) 

x Check 

communications 
wiring (data 1/ data 2 
wires) 

x Check wire 

connections at 
terminal block 

x  Check data 1/ data 2 

voltages 

x Turn power OFF 

prior to repair 

x Verify wires at 

terminal blocks are 
securely twisted 
together prior to 
inserting into 
terminal block 

x  Verify data1 and 

data voltages as 
described above 

 

The normal power up sequence is as follows:

•

115 VAC power applied to furnace.

•

Integrated control module performs internal checks.

•

Integrated control module displays 

88888     88888 on dual 7-segment

display LED’s.

•

Integrated control module monitors safety circuits
continuously.

•

Furnace awaits call from thermostat. Dual 7-segment
LED’s display 

00000     PPPPP while awaiting call from thermostat.