LAARS Mighty-Stack TL00-199 - Installation, Operation and Maintenance Instructions - Manual (Page 20)

LAARS HEATING SYSTEMS Page 20
Figure 16. Troubleshooting Flowchart.
YES
NO
Turn gas supply
off. Set aquastat
to call for heat.
Is gas valve
powered? (Should
be 24V AC)
YES
NO Does igniter warm
up and glow red?
YES
NO Does pilot valve
open?
YES
NO
Turn gas on.
Does pilot burner
light?
YES
NO Does main gas
valve open?
System is OK.
Check:
• On/Off toggle switch
• Line voltage/power
• Low voltage transformer
• Limit controller
• Aquastat
• Wiring
• Fan proving switch on combustion
air blower
• Roll-out switch (inside cabinet)
Unplug igniter, measure voltage at
two bottom terminals of gas valve.
Is this 24V AC?
Replace igniter. Replace gas valve.
Replace gas valve.
Measure voltage to gas valve. Is volt-
age at least 19.5V AC?
Replace igniter.
Check transformer and
line voltage
Replace igniter sensor and save it.
Repeat the troubleshooting sequence.
Does main valve open?
Discard old igniter sensor.
NO YES
YES NO
YES NO
Replace gas valve.
Re-use old igniter-sensor.