Trouble chart – Midco F400-33 User Manual
Page 10
TROUBLE CHART
MAKE SURE THE THERMOSTAT AND OPERATING CONTROLS ARE CALLING FOR HEAT.
CAUTION: If a test indicates an electrical component may be defective, before
replacing it, make sure that its associated wiring is not at fault.
1.
MOTOR WILL NOT RUN.
A.
No current.
B.
Defective or misadjusted limit or thermostat.
C.
Flame safeguard control on lockout.
D.
Defective flame safeguard control.
E.
Motor overload out.
F.
Defective motor.
2.
MOTOR RUNS, PILOT WILL NOT LIGHT, FLAME
SAFEGUARD LOCKS OUT.
A.
Air in pilot gas line.
B.
Low gas pressure.
C.
Clogged pilot orifice.
D.
Pilot regulator misadjusted or defective.
E.
Defective spark electrode or spark generator.
F.
Defective high tension wire.
G.
Wrong pilot orifice.
H.
Defective pilot valve.
I.
Pilot air tube clogged.
J.
Incorrect spark gap.
K.
Pilot regulator vent clogged.
L.
False flame signal; flame safeguard
control.
M.
Defective flame safeguard.
3.
MOTOR RUNS, PILOT WILL NOT LIGHT, FLAME
SAFEGUARD REMAINS "SET."
A.
Defective centrifugal actuator.
B.
Defective blower interlock switch.
C.
Slow motor.
D.
Defective purge timer.
E.
False flame signal.
F.
Defective flame safeguard.
4.
PILOT LIGHTS, NO MAIN FLAME, RELAY
LOCKS OUT.
A.
Poor pilot flame adjustment.
B.
Clogged pilot air tube.
C.
Defective flame rod or wire.
D.
Flame rod mislocated.
E.
Spark interference.
F.
Pilot regulator vent clogged.
G. Defective plug-in amplifier.
H.
Defective flame safeguard.
5.
PILOT LIGHTS, NO MAIN FLAME, RELAY
REMAINS "SET."
A.
Defective main gas valve.
B.
Closed leak test cock.
C.
Low gas pressure.
D.
Grossly misadjusted main gas and air.
E.
Defective flame safeguard.
6.
SPASMODIC START.
A.
Loose wiring.
B.
Low gas pressure.
C.
Poor pilot flame adjustment.
7.
SHORT FLAME.
A.
Wrong main orifice.
B.
Low gas pressure.
C.
Air shutter misadjusted.
D.
Main regulator misadjusted.
E.
Test cock partially closed.
F.
Main regulator vent clogged.
8.
LONG HAZY FLAME.
A.
Wrong main orifice.
B.
High gas pressure.
C.
Dirty blower wheel.
D.
Air shutter misadjusted.
E.
Main regulator misadjusted.
9.
GAS FAILS TO SHUT OFF.
A.
Dirt on valve seat(s).
B.
Defective main valve(s).
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