Monitor 41 alarms off on two burner lights

[Heinrich]

This is the second Monitor 41 installed over the past 25 years. Combustion chamber was overhauled about 4 years ago. Continues to work well in all modes EXCEPT when holding temperature overnight on two burner lights. More often than not, heater turns off early in the morning with 8 burner lights flashing. Since problem is on lowest burner setting, Air Pressure SW was suspect. Hose to SW is very flexible with no cracks. Can hear contacts closing when blowing into hose lightly. Pressure switch could be on the edge of breaking contact, so operating with two burner lights went outside and blocked half of air intake - heater did not turn off. Have large fuel filter on outside tank, tank is tilted down away from outlet - haven't had water in kerosene issues. Have been vacuuming heat exchanger and blower guard even though not very dusty.

Removed hose to Pressure SW, removed air intake hose and vacuumed what appeared to be a very clean Blower. Both vent pipes clear - vacuumed anyway.

Flames in burner are bright blue on all burner settings and only see small orange flashes for a short time when firing up, and after burner settings change. No soot on window. Circulation Fan, Blower Assembly and Solenoid Pump operate quietly.

Since heater operates on 8. 6 and 4 burner lights, assume Constant Level Valve and Solenoid Pump are OK?

Could it be damper solenoid - how to test it? Could it be crap on Flame Sensor - how to test it?

Heinrich

[HayZee518]

8 flashes mean lack of something. remove the flamerod and clean it. probe tip must point down and be between burner ring and side of pot. physically remove the fuel sump and clean it out. the M41 uses a mechanical toggle over center lockout actuated by a spring and float. when water mixes with fuel it forms a brownish slime which settles on the bottom of the sump. If left for any length of time, it will rust the metal parts of the lockout. It must be cleaned out. a 9/16" open end wrench will loosen the gland nut on the fuel inlet pipe. The damper solenoid is not visible when its in operation. when it does work you can hear a clunk when it opens as the heater shifts into high heat. If your air proving switch was not functioning properly, its position in the circuit would prevent the fuel solenoid from operating. when the unit goes into the prepurge cycle the switch should be closed. the igniter should be on at all times. the bottom of the pot will be warm to the touch.

[hawkins111]

Four years is about average for a M41, M441to go before you need to look into the burner and replace the burner cloth and burner ring. When the cloth gets hard with carbon or lifts off the bottom the flame will waver and get off the sensor. The ring will warp and cause the flame to waver also. As stated before, clean the flame sensor to be sure it does not have a small spot of carbon on the tip. That may get you down the road a ways, but you will need to open the burner sometime soon. Tom

[Heinrich]

Does damper solenoid only operate on high heat (8 burner lights)? What is purpose of damper solenoid?
Is air proving switch the air pressure switch connected by hose to blower?

[HayZee518]

the air damper is a rectangular piece of plastic or fiber in-line with the air flow from the combustion blower. it is operated by an electro magnetic solenoid coil. when actuated it pulls down on a lever which opens the air flow to maximum. more fuel needs more air to burn. the air proving switch is mounted on the large circular pancake shaped alumiinum can with one or two hoses coming out of it. there's a diaphragm inside that flexes and closes a microswitch.

[Heinrich]

Thanks for your help - now know what to do - signing off

[Heinrich]

Appreciate your help - now know what to do - signing off