Table C4 System and General Troubleshooting

TABLE C4: SYSTEM AND GENERAL TROUBLESHOOTING

Problem		Possible Cause	Remedy
		Thermostat not calling for heat.	Check thermostat and adjust. Also, check thermostat for accuracy; if it is
		Thermostat not calling for heat.	a mercury switch type, it might be off level.
			a mercury switch type, it might be off level.
			Check furnace switch, main electrical panel furnace fuse or circuit
		No power to furnace.	breaker. Also look for any other hand operated switch, such as an old
		No power to furnace.	poorly located furnace switch, which was not removed during furnace

			replacement.
Furnace will not start.
Furnace will not start.			Remove thermostat wires from oil primary control terminals T-T. Place a
		Thermostat faulty.	jumper across T-T. If furnace starts, replace thermostat, thermostat sub-
			base (if equipped), or both.
			Check reset button on oil primary control. Remove thermostat wires
		Oil primary control faulty.	from oil primary control terminals T1 - T2. Check for 24v across T -T. If
		Oil primary control faulty.	no voltage is present, check for 115v to oil primary control. If 115v is

			present, go to Table C-3.

		Photo Cell wiring shorted or room	Check photo cell (cad cell) wiring for short circuits. Also, check for room
		light leaking into photo cell	light leaking into cad cell compartment. Repair light leak if necessary.
Furnace will not start.		compartment	See Table C-3.
		Open safety switch.	Check for open limit or auxiliary limit. Also, check internal wiring
		Open safety switch.	connections; loose connectors, etc.
			connections; loose connectors, etc.
		No fuel oil.	Check fuel oil supply. Check that all hand operated fuel oil valves are in
		No fuel oil.	the open position. Fill oil storage tank if necessary.
			the open position. Fill oil storage tank if necessary.
		Clogged nozzle.	Replace nozzle with high quality replacement. Use rating plate or Tables
		Clogged nozzle.	in Appendix A as a guide.
			in Appendix A as a guide.
Furnace will not start without		Clogged oil filter.	Replace oil tank filter or in-line filter if used.

			Connect pressure gauge to oil pump. Adjust pump pressure, or replace
first pushing oil	primary	Low oil pump pressure.
control reset button.		Low oil pump pressure.	oil pump if necessary. Ensure that erratic pressure readings are not
(Happens on frequent basis)			caused by defective fuel oil line.
		Air getting into fuel oil lines, or fuel	Check fuel oil lines. Replace any compression fittings found with high
		oil line dirty, clogged, or in some	quality flared fittings. Check for any signs of oil leaks. Any oil leak is a
		manner defective.	potential source of air or contaminants.
		Defective burner motor.	Check burner motor. If burner motor is	cutting out	on over-load,
		Defective burner motor.	determine why. Replace if necessary.
			determine why. Replace if necessary.
			If cad cell is dirty, clean it. (Determine why cad cell is getting dirty). If
Furnace starts, but cuts out		Photo Cell (Cad Cell) defective.	cad cell is poorly aimed, realign it. NOTE: The photocell should have a
requiring manually	resetting	Photo Cell (Cad Cell) defective.	resistance of 100K Ω in absence of light; a maximum of 1500 Ω in the
the oil protector reset button.			presence of light. Ensure that room light is not leaking into the cad cell
			compartment. (See diagnostic light section).
		No fuel oil.	Check fuel oil supply. Check that all hand operated fuel oil valves are in
		No fuel oil.	the open position. Fill oil storage tank if necessary.
			the open position. Fill oil storage tank if necessary.
		Clogged nozzle.	Replace nozzle with high quality replacement. Use rating plate or Tables
		Clogged nozzle.	in Appendix A as a guide.
			in Appendix A as a guide.
		Clogged oil filter.	Replace oil tank filter or in-line filter if used.

		Low oil pump pressure.	Connect pressure gauge to oil pump. Adjust pump pressure, or replace
		Low oil pump pressure.	oil pump if necessary. Ensure that erratic pressure readings are not
Furnace starts, but cuts out			caused by defective fuel oil line.
requiring manually	resetting	Air getting into fuel oil lines, or fuel	Check fuel oil lines. Replace any compression fittings found with high
the oil protector reset button.		Air getting into fuel oil lines, or fuel
the oil protector reset button.		oil line dirty, clogged, or in some	quality flared fittings. Check for any signs of oil leaks. Any oil leak is a
		manner defective.	potential source of air or contaminants.
		Defective burner motor.	Check burner motor. If burner motor is	cutting out	on over-load,
		Defective burner motor.	determine why. Replace if necessary.
			determine why. Replace if necessary.
		Water or contaminants in oil.	Drain fuel oil storage tank, replace fuel	oil. (Consult	with fuel oil
		Water or contaminants in oil.	supplier).
			supplier).
		Frozen oil line.	Gently warm oil line. Insulate oil line. (Outdoor piping size may require
		Frozen oil line.	increased diameter).
			increased diameter).

29	30318 R4 9/9/2005

MPL-B, WML-C specifications

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Field Controls MPL-B Table C4 System and General Troubleshooting, Problem Possible Cause Remedy

Models: MPL-B WML-C

TABLE C4: SYSTEM AND GENERAL TROUBLESHOOTING

Problem

Possible Cause

Remedy

30318 R4 9/9/2005

MPL-B, WML-C specifications