Thermo Pride Gas/Propane Furnace Induced Draft Highboy/Counterflow/Horizontal MHA1 - Manual (Page 48)

All installations and services must be performed by qualified service personnel.
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APPENDIX C: TROUBLESHOOTING FLOWCHARTS
A. Heating System
Set thermostat subbase to "HEAT".
Does thermostat make contact?
Yes
Is room temperature
above thermostat setting?
No
Is the transformer supplying
24 VAC to the thermostat ?
Yes
No
Replace thermostat.
Yes
Are the thermostat wires connected
properly?
Replace control transformer.
Correct wire
connections.
No
Is there 24 VAC across
"TH" & "TR" terminals of the
ignition control module.
Turn thermostat setting
above room temp.
Is the inducer
blower operating?
Yes Yes
Check for continuity
& proper connections
No No
Yes
No
Yes
Check input power,control
system fuse,disconnecting
switch and fuses (if equipped).
Is the control transformer
receiving 120 VAC?
No
No