monitor 441

[Spike]

I have a 10 yr old 441 and i'm having problems with it staying running.
It starts goes thru it's purge,fires up on low, and switches to high.
Runs about 2 mins on high and shuts down.
I've cleaned the flame sensor and fuel tube as descibed in other threads.
It appears to be burning fine when it runs and the tip of the flame sensor is glowing red.
Just before the shut down the panel flashes one time then it turns off on a safety and flashes
i can hear the fuel soleniod stop for a second when the panel flashes come back on for a second then shuts off. It doesn't appear to be a fuel issue.
Intake fan seems to running with no issues, great air flow out the exhaust pipe

The fan switches from low to high with the burner increase and i checked the high temp limit switch which isn't causing the shut down.

I guessing the flame sensor is shot even though it's clean and in the proper location but can't believe it would run that long with it being bad.
Is the some type of thermostat that makes the unit get to temp and go back to slow burn that may have failed

Anything else i should check before replacing the sensor?
thanks

[HayZee518]

easiest way to check the flame sense electronics is to use a 1N4004 diode in series with a 100K resistor. a couple of pieces of hookup wire and two alligator clips. ground one side of the test setup and when the unit goes into high heat, hook the other alligator clip to where the red wire goes into the motherboard. if the electronics are ok the heater should keep right on firing and running. if it shuts down then there is another problem, possibly with the high limit. that's the klixon on top of the inner plenum sheet metal just below the top cover. I have a kero 2400 unit here at my house. when condensate gets into the kero tank it forms a brownish colored water ewww crap in the bottom of the tank. I pumped out about 3 gallons of water out of my tank. next time you take apart the fuel sump, look inside for the brown crap and clean it out. it'll gunk up any mechanical lockout devices inside and might inhibit the float from moving.

[Spike]

Thanks for the info. I'll try to get the bypass hook up this week and test it.
The fuel tank and filter is new this yr so I'll clean the fuel sump out again.
I checked the power in and out on the high temp limit switch and it had power in and out so i'm guessing it's not the problem
Thanks again

[HayZee518]

I fergot to mention that when you use the test setup if it don't work one way reverse the leads. The diode/resistor simulates what the flame rod is doing, that is, it changes its polarity from AC to DC in the presence of a flame. Just a querky phenomenum of a flame rod. Actually the flame ionizes the air so it electrically conducts. same thing happens in a plasma arc cutter. the overtemp switches are the two mounted on the front of the plenum plate. they are connected in series and then to the mother board. the solenoid pump has a nylon filter screen on it and it rotates but won't come off so don't force it off. I took my sump tank apart yesterday to clean that brown crap out of it.

[Spike]

Thanks for getting back so quickly
There are two temp switches on the front in series and one on the top.
By chance do one of them tell the burner to drop back to the low setting?
I've got a feeling that one may be bad and not telling it to slow down to low burn and shutting it down on high temp with the other.
The plenum was really hot to the touch when it shut down, much more than what i would think it should be. I was thinking that they were fan stage switches but if they are burner temp sensors it would explain how it knows when to slow back to low burn. it would work like a dryer.
I'm guessing the switches are fairly cheap and it may be worth it to change them both because they look like a bear to get at.
Thanks

[adnadeau]

The fuel pump will run for exctly 2 minutes and then shut off if the flame detector circuit isn't working. You might check the green "ground" wire that runs from the circuit board to a screw on the heater frame. That's the other half of the flame detector circuit.

[Spike]

thanks Adnadeau.
I'll check that tonight.
I'll also time the cycle before the safety shuts it down

[Spike]

Ok here's what i have in a time frame.
purge cycle runs 4 min then switches on the pump solenoid and igniter.
low burn starts,i can see flame, about 1 1/2 to 2 mins into this cycle.
3.5 mins in the fan starts on low speed
It runs about 4 mins in low burn cycle then switches to high burn.
It's been running with flame for 6 mins now and the fan kicks into high speed. The plenum temp is around 90 degrees.
It contunes for 5 more mins on high burn then the burner light flashes once and the solenoid pump stops then comes back on for a couple seconds more then everything except the blower fan shuts down and the burner lights stay flashing.
Plenum temp was 169 degrees when it shut down.
That seems way to hot for normal run temp
It ran almost twice as long tonight but the garage was 25 degrees cooler than the other day when it ran less time.
I'm hoping that one of the 2 temp sensors in series on the front right controls the burner status and it has failed causing the overheat one to shut it down.
I did check the flame sensor ground wire and it was tight and clean.
The other sensor on top right is definitely the fan, power passed through it and the fan kicked into low speed.

Am i on the right track in thinking the lower one in the series is probably the sensor that switches the unit to low burn stage and the upper one is the over heat safety?
Anything else i can test?
Any help is greatly appreciated
thanks

[hawkins111]

M441 trouble

Spike,

You are a little off when it comes to the two switches on the heat baffle. That is the over heat circuit. There are two switches in that circuit in series for redundancy. From what you have written most everything seems to be right. If you get your flame sensor bypass hooked up your stove will run. That does not mean the flame sensor is bad. There is very little that can go bad with the flame sensor. The wire can break, the porcelain can crack and you can make it touch the side of the pot. Short of that the flame sensor is good and is doing exactly what it is supposed to do. When it does not sense a proper flame it shuts the stove down. Since your stove is 10 years old I would say you need a combustion chamber overhaul. A M441 will only go so long before the pot needs to be cleaned and a new mat and ring installed. Before you do that make sure the fuel filter has been changed and bled, the filter on the stove is clean and there is enough fuel in the tank to feed the stove. Five or 6 inches in the tank is not enough. Be sure the flue pipe does not have a hole in the exhaust side and the vent is clear on the tank. There is a small black hose that goes from the blower to a switch on the base of the unit that needs to be connected and not cracked. Last but not least the circulating fan is spotlessly clean. If all that is good and the stove still cuts out, you need to proceed with the combustion chamber.

Tom

[Spike]

thanks Tom for getting back to me.
It's nice to have experts pointing me in the right direction

The burner was rebuilt 5 yrs ago and a new mat installed with a new burner ring. I can put another mat in if you think that will solve the problem and clean the burner ring.
Flame is a bit yellow on top but turns blue down around the burner ring once the heater warms up.
I cleaned the flame sensor twice, no breaks in the porcelian, and made sure it's away from the burner metal. I can see it turn red on the tip has the heater warms up through the window
I checked the pressure switch tube along with the intake tube and cleaned the blower fan. Both appear to work properly with no leaks anywhere on the purge fan side.
Fuel tank is new ,3/4 full ,and i pre-cleaned it and installed a brand new filter.
I also cleaned the units filter before installing the heater but will check it again.
How hot does the plenum get before the safetys kick in or is it possible one has lost it's set temp limit cause the unit to shut down?
I can try removing them from the plenum and see what happens next if you think that might rule them out
I'm working on getting the flame sensor deal built so i can by pass it and see what happens.
Hopefully this weekend i can try this
Thanks again for your help

[HayZee518]

The heat thermostats if you want to call them that are devices called "klixon" the cutout/cutin temperatures are usually stamped in the metal.
They were originally made for embedding in motor windings as thermal cutout devices because of over current. As amps went up so did the working temperature of the motor. Before the motor would burnup its windings the thermal device cutout the control circuit for the motor. Later today i'll post a few pictures of the water i got out of my fuel tank outside and a pump i purchased to pump out the condensate water in the tank

[HayZee518]

Monitor heater external tank

The following are pictures I took of the water and crap that came out of my outside kerosene tank. The larger jars are of the 1 gallon size, the middle one is half gallon
The pump is a lever operated lifting pump from tractor supply

[Spike]

That's some water!!!
I'm pretty certain i don't have any in my tank since it's only 2 months old with 3/4 full with fresh fuel
I'm pulling the Monitor apart tomorrow.
I purchased a new burner mat, cap and gaskets. I'll definitly check the fuel filter and sump on it while i tear it down.
I saved the original burner ring, the thing with the small holes in it on the bottom, because we ordered a new rebuild the last go round 5 yrs ago.
It seems straight so i'll clean it and the fuel tube up,put in the new mat with the special high temp cement and put it back together cleaning everything again.
The cap seems straight though the window but for the $50 i'll change it while i'm in there and save the old one if it looks ok.
Hopefull this makes it run
My flame sensor by-pass will be completed today so i'll test this next if doesn't stay running with all the new parts. I'm hoping not to need it but it will be a good tool down the road if i don't use it now

I appreciate everyones help on this.

[Spike]

you guys are the monitor gods!!!!

I put in the flame rod test/by pass piece in and the unit ran through a complete cycle.The only thing i had to do different was hook up the by pass part as soon as i saw flame. if i waited for the unit to shift to high it would go into a safety shut down.
Strange thing is that it's run great ever since, it's been running 5 hrs now and cycled at least 10 times. Everything from a complete cold start up to low burn cycle to high and back to low
Maybe a piece of soot just touched the flame rod once and awhile while it was firing but since it made it's first full cycle it's been fine.
Either way it's getting a burner pot switch out tomorrow with a good clean out.
I can't thank you enough, your the greatest

[Spike]

well the unit ran all night with no failures.
I tore it down this AM and replaced the burner and cap.
The old old burner had some soot in it and the cap was slightly warped on the back side away from the flame sensor.
Re-installed everything and it's burning like it's new again with a beautiful blue flame. I found one added feature right under the burn pot, one very dried out baby dead mouse in the elbow . i guess that would make it burn rich.

You guys are the best!!!!
Thank you