m21 heater quit working, flashing

[rrob311]

After putting a few tanks through my m21 heater, I came home to find it flashing and shut off. It seems to be a constant flashing, so I reset it and started it up, the low burn comes on and you see a nice blue flame in the chamber, then before the blower fan kicks on it just shuts off and starts flashing. It seems to be getting enough fuel because there is still flame when it shuts off. Are there any codes that these things spit out? Where should I start diagnosing it? I looked at the manual but don't know where to start.

Another thing I noticed the other day (when it was working) is that when I set the heater to like 60, sometimes the burner will stay on low when the room temp is like 64, 66, etc, then the only way I can get the heater to stop is by lowering the temperature more.

[HayZee518]

a two to four degree overshoot is normal. also when the thermistor is disconnected or is faulty the unit defaults to 42 degrees. it'll stay running no matter where the setpoint is at. flashing lights means the unit went into lockout. this can be caused by a piece of soot or carbon shorting out the flamerod. when the unit shuts down residual kero in the burn pot burns off, that's where you see the yellow flames.

[rrob311]

a two to four degree overshoot is normal. also when the thermistor is disconnected or is faulty the unit defaults to 42 degrees. it'll stay running no matter where the setpoint is at. flashing lights means the unit went into lockout. this can be caused by a piece of soot or carbon shorting out the flamerod. when the unit shuts down residual kero in the burn pot burns off, that's where you see the yellow flames.

So the carbon soot conducts electricity? I need to get this one going here in the coming weeks.

[hawkins111]

You need to look into the burner pot and see what the combustion ring looks like. The flame sensor might be touching the ring because the ring has mushroomed from use.

[HayZee518]

carbon is CARBON - there really isn't different forms of carbon. AND YES, CARBON IS CONDUCTIVE. When Edison invented the light bulb, he rubbed candle carbon on a silk thread for his filament and passed an electric current through it.

[rrob311]

whats the easiest way to access the combustion ring. This unit seems way harder to take apart than the model 41 heater.

[rrob311]

I took out the flame rod and the end is bent. From looking at it it looks like it may have been grounded out on something. But it looks like a big job to access the burner ring. Do I have to take the chamber and exchanger assembly out of the unit to access it?

[hawkins111]

Yes, you have to take the combustion chamber and heat exchanger out of the unit and flip them upside down. Keep them together unless the heat exchanger is very dirty.

Tom

[rrob311]

OK I got it torn down and the burner ring is worn out big time, the burner pot is also full of carbon on one side. Is a lot of buildup common when burning kerosene or would it be safe to say maybe diesel or heating oil was used in it?

[hawkins111]

Nobody deliveries Kerosene to homes anymore. You will get #1 Home Heating oil which is almost as light as kerosene and approved for use in Monitor heaters. It is very safe to say that the heater has been running for a long time since it has been serviced. If the bottom of your pot is not warped you can install a new mat and burner ring and new gaskets. This should make your heater run for 3 to 5 years without much trouble. If you use the Economy Plus feature you will get a few more years out of it before you need to service it all over again. Merry Christmas, Tom

[rrob311]

I had to use a needle scaler to clean the pot but it worked without damage. I also cut a burn mat so we will see how it works. Have you ever tried grinding the protruding edges off the burner ring and put them back in service? Will it work for longer that way? Merry Christmas as well. Stay warm, it was -6f this AM here in NH.

[hawkins111]

Your old burner ring is unserviceable and must be replaced.

[OnTheEdge]

I agree with Tom. Anything you can do to try to fix, patch or otherwise repair the old burner ring would be a temp halfass fix at best.

For 75 bucks it is short $$ and not worth the time and effort to tear the unit down again after a short time to replace it when it fails again..

[rrob311]

OK I am in the process of reassembly and it seems the igniter fits loosely when I screw it down. What thickness gasket am I supposed to use and what is a suitable material?

[OnTheEdge]

MONITOR HEATER 6115 HEATER IGNITER GASKET M21, M22, M40, M41, M2200, M2400 | eBay