LAARS HEATING SYSTEMS
Page 22
Troubleshooting Honeywell S8600
Intermittent Pilot System (Spark Ignition)
Some models are equipped with lockout/retry modules. On L.P.G. models, trial for ignition last
15 seconds followed by 5 minutes lockout, then the cycle repeats.
START
Turn off gas supply.
Turn thermostat (Controller) to
call for heat.
Power to module (24V nominal).
Spark across igniter/sensor gap.
Turn gas supply on.
Pilot burner lights?
Spark stops when pilot is lit?
Main burner lights?
System runs until call for heat ends?
Call for heat ends. System shuts off.
Check line voltage power, low voltage transformer, hi-limit switch, thermostat
(controller) and wiring.
NOTE: Before troubleshooting, familiarize yourself with the start-up and checkout
procedure.
Put ignition lead and check spark at module. Spark okay?
• Check ignition cable ground wiring, ceramic insulator and gap and correct.
• Check boot of the ignition cable for signs of melting or buckling. Take protective
action to shield cable and boot from excessive temperatures.
• Check that all manual gas valves are open, supply tubing and pressures are good,
and pilot burner orifice is not blocked.
• Check electrical connections between module and pilot operator on gas control.
• Check for 24 Vac across PV-MV/PV terminals on module. If voltage is okay, replace
gas valve; if not, replace module.
• Check for 24 Vac across MV-MV/PV terminals. If no voltage, replace module.
• Check electrical connections between module and gas valve. If okay, replace gas
valve.
NOTE: Some models are equipped with lockout/retry modules. On L.P.G. models, trial
for ignition lasts 15 seconds followed by 5 minutes lockout, then the cycle repeats.
• Check continuity of ignition cable and ground wire.
• Clean flame rod.
• Check electrical connections between flame rod and module.
• Check for cracked ceramic flame rod insulator.
• Check that pilot flame covers flame rod and is steady and blue.
• Adjust pilot flame.
• If problem persists, replace module.
NOTE: If S8600H goes into lockout, reset system.
• Check continuity of ignition cable and ground wire.
NOTE: If ground is poor or erratic, shutdowns may occur occasionally, even though
operation is normal at the time of checkout.
• Check that pilot flame covers flame rod and is steady and blue.
• If checks are okay, replace module.
• Check for proper thermostat (controller) operation.
• Remove MV lead at module; if valve closes, recheck temperature controller and
wiring; if not, replace gas valve.
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
