Suburban SF-20F Service Manual

34
?-Yes-< Replace the
sail switch.
Yes No
?
?
-Yes-<
Replace the
limit switch.
?
-No-< Replace the module.
? Yes
?
-No-<
Replace the
module.
? Yes
?
?-No-< Check gas
pressure at the manifold or for
restrictions in the burner orifice.
? Yes No
? ?
Yes
Replace the gas valve.
? No
?
?-No- Check flame
contact to electrode. Flame should
be hard blue.
Thermostat opens and the time delay
operates the fan for the cool down cycle.
-No-<
Replace the time delay relay.
Yes
NOTE: On some models, sail switch is before limit switch.
TROUBLE SHOOTING GUIDE SUBURBAN RV FURNACE with FAN
CONTROL MODULE BOARDS 12 VDC HEATING SECTION
Check thermostat wire connections, Clean points, secure loose
Thermostat Closes -No-< contact points and the heat -Yes-< connections, replace thermostat if
anticipator. anticipator is shorted.
? No
?
? Check 12vdc at blue wire, check the -Yes-
<
Replace thermostat.
amp draw to thermostat.
Yes No
?
? Check for shorts. -Yes-< Repair or replace connections or parts
Check components amperage. with higher than normal amp draw.
? Yes
Check for 12vdc at furnace -No-< Check on/off switch on furnace
? Yes
?
Check fuse or circuit breaker -No-< Replace fuse/Reset breaker.
? Yes
?
-No-< Check for 12vdc at power terminal on -No-<
Check for 12vdc at limit switch, both
sides.
Check for 12vdc at sail switch both
sides.
Spark occurs for approximately
7 seconds and main burner flame establishes.
-No-<
No spark at the electrode
Check for 12vdc at gas solenoid valve.
Did the gas valve open.
Check for restriction in combustion air
Intake (wasps, etc.)
Is flame established.
System Ok

Suburban SF-20F Specifications

General

Brand	Suburban
Model	SF-20F
Category	Furnace
Language	English