Thermo Pride GMC-85 Installation And Service Manual page 33

All installations and services must be performed by qualified service personnel.
Set thermostat subbase to "HEAT"
Does thermostat make contact?
Yes
Is room temperature above
Does a "call for No
heat" initiate an Is the power switch "off"?
ignition cycle?
across lines L1 & L2?
Yes
Is the control transformer
(GMC) or oil primary control
(OMC) receiving 120 VAC?
No
Is room temperature
above 90 deg. F?
No
thermostat setting?
No
Replace thermostat
No
Is there 120 VAC
Yes
Yes
OMC/GMC TROUBLESHOOTING FLOWCHART
Yes
Wait for room air to cool.
Yes
Turn thermostat setting
above room temp.
Yes
Turn power
switch "on".
No Check input power. Reset circiut
breaker, or replace blown fuse in
disconnected switch.
No Have either of the
high limit thermostats
activated?
With power on,measure
voltage across the aux.
high limit thermostat N.C.
contact to L2. If not 120 VAC,
replace aux. high limit
thermostat. Else,replace
high limit thermostat.
32
Wait for furnace to cool.
Look for cause(s) of high
Yes
limit activation,eg. low
airflow, over-firing,
blocked flue,etc..
Correct any
abnormal conditions.
No