S86 Checkout And Trouble Shooting - Garland MCO-GD-10M Service Manual

and answering conditions in each box encountered, until a problem and/or the repair is explained.
maintenance or repair, the trouble shooting sequence should be repeated until the trouble shooting procedure ends
with a normal system operation.
START
TURN GAS SUPPLY OFF.
TURN THERMOSTAT
(CONTROLLER) TO CALL
FOR HEAT
POWER TO MODULE (24v
NOMINAL)
YES
SPARK ACROSS
IGNITOR/SENSOR GAP
YES
TURN GAS SUPPLY ON
PILOT BURNER LIGHTS?
YES
SPARK STOPS WHEN
PILOT IS LIT?
YES
MAIN BURNER
LIGHTS?
YES
SYSTEM RUNS UNTIL
NO
CALL FOR HEAT
LOSS?
YES
CALL FOR HEAT ENDS
SYSTEM SHUTS OFF?
YES
TROUBLESHOOTING
ENDS

S86 CHECKOUT AND TROUBLE SHOOTING

NO
Check line voltage power, low voltage transformer, limit controller, thermostat
(controller) and wiring.
Pull ignition lead and
check spark at module.
NO
Spark okay?
YES
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 temperature.
Check that all manual gas valves are open, supply tubing and pressure are good,
and pilot burner orifice is not blocked.
Check electrical connections between module and pilot operator on gas control.
NO
Check for 24 Vac across PV-MV\PV terminals on module. If voltage is okay,
replace gas control; if not, replace module.
NOTE: If S8600B,H; S8610B, H goes into lockout, reset system. For S8600M,
wait 6 minutes nominal for retry or reset system.
Check continuity of ignition cable to ground wire.
Clean flame rod.
NO
Check electrical connection between flame rod and module.
Check for cracked ceramic flame rod insulator.
Check that pilot flame covers rod and is steady and blue.
Adjust pilot flame.
If problem persists, replace module.
Check for 24 Vac across MV-MV\PV terminals. If no voltage, replace module.
NO
Check electrical connections between module and gas control. If okay, replace
gas control or gas control operator.
NOTE: If S8600B,H; S8610B, H goes into lockout, reset system. For S8600M,
wait 6 minutes nominal for retry or 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.
NO
Check for proper thermostat (controller) operation.
Remove MV lead at module; if valve closes, recheck temperature controller and
wiring; if not, replace gas control.
Repeat procedure until troublefree operation is obtained.
NOTE: Before troubleshooting, familiarize yourself
with the startup and checkout procedure.
On models with vent damper plug, make sure vent
damper had not been installed, then remove.
NO
Replace vent damper if necessary.
On other models, replace module.
14
After any