A certain person who you may run into on the internet is Al Luce. He is a self proclaimed monitor guru, who badmouths the very equipment he [used] to service. I say “used” is because he supposedly redesigned the whole monitor heater with above factory quality parts. That being said let us continue……
The monitor is a very technical and straight forward piece of home heating machinery. It is computer controlled and has engineered safety factors.
The unit functions basically like any other furnace except the fact that it is direct vented. It receives its input air in the same pipe that exhausts its gases. Kerosene is its prime fuel and it don’t like stove oil #2 or diesel or bio diesel. Using diesel or biodiesel will certainly gum up the works. The monitor uses a flame detector, an electric igniter, a solenoid operated fuel pump, a fuel lockout device so you don’t flood out your heater area. It has its self contained fan with three speeds. It uses a modified vacuum motor and impeller to provide combustion air. Monitor models 20, 40, 41 are basically the same with a few new innovations. Monitors #441 and 422 are once again improved but in small ways. Monitors #2200 and 2400 are more advanced but the only difference is the Btu output between the two and the use of an internal fuel canister.
Now let’s take apart a MONITOR M41.
Unplug the cord. Go outside and unscrew the stainless steel collar/nut, slide back the rubber wall seal. CLOSE the fuel line at the tank. Go back inside and use some rags underneath the fuel line at the back of the unit and crack loose the flare nut on the fuel line and unscrew it. Kerosene will come out.
Carefully pull the unit away from the wall until the exhaust tube is inside the house. Pack a rag into the opening to keep out critters and cold air if you’re doing this in the winter.
Loosen up the clamp on the rubber flex hose coming from the combustion blower to the twin exhaust/inlet tube and pull it off the tube. Grab hold of the twin tube with the offset adapter and rock it back and forth and pull it out of the unit. Check inside – it may have lots of soot built up inside – brush and vacuum it out. Compressed air helps too!
If the flex tube has any cracks replace it.
Look at the top of the grill. You’ll find three Phillips screws. Remove these and pull out the grill. This will expose the flamerod, view port, combustion pot, the lower half of the computer board, fuel solenoid pump, fuel sump and air switch. Deeper inside is the combustion blower, rubber elbow and aluminum tube.
Lower yet on the cabinet front are two screws – remove these and the bottom plate will come off – lift up and out. There’s two hooks on either end that disengages from the cabinet uprights. You can now see the rest of the aluminum air tube and the other rubber elbow that connects the tube to the bottom of the combustion pot.
The top of the unit has two Phillips screws on two sides and two on the rear. Remove the top by lifting up on the rear and tilt it up and front ways and lift it off. Under here you’ll see the fan start limit with two wires on it, two overheat switches with a jumper between them and two wires that go back to the computer board. Remove the front plate with the display by pulling out and up. Two hooks engage the unit uprights in slots. Be careful because the display connects to the computer with four ribbon cables. Gently remove the ribbon cables. These are keyed so they’ll only go in its respective socket.
On the left is a sheet metal panel three screws on top and two screws in front. Take these out and the top lifts off. Unplug the wires. Make note of where these wires go – a couple of them connect to one point the other has a keyed molex plug.
The top of the combustion pot has a round cover with a tab to the left. Remove all screws and gently lift the top plate. There’s a gasket underneath – try not to shred it.
Look inside – you’ll see the FLAMEROD, COMBUSTION RING [looks like an inverted bowl. Around the perimeter of the combustion ring look for all those tiny holes! These must be rust and soot free if the heater is to function properly.
Remove the flamerod first – you don’t want to go breaking this thing. Two Phillips screw go through a bracket and the flamerod comes out by rotating it one way or another. One wire connects it to the computer board. The combustion ring is held down in three spots with spring clips. Rotate the ring clockwise and gently depress the spring clips. The combustion ring may be badly warped but the fastening ring will keep its roundness.
Beneath this is the igniter, fuel outlet and burner mat. There’s a brass sleeve they call the outlet tube extension. This is free to move. The igniter is a ceramic tube with a heating element inside. This is very brittle – BE CAREFUL! It is removed by taking out three screws outside the combustion pot bottom and removing two screws on a bracket.
Certain parts you have to get from Monitor. The combustion ring costs around 72.50. The combustion pot port gasket costs around 16.50 BUT you can get around this by buying sheet gasket material from McMaster-Carr Industrial supply. They have a material that is of a silicate base and is woven and its high end heat rating is higher than monitor’s. 2008 catalog page is 3372 part is 8813K11. The gasket material used for the burner mat is page 3409 part 8838K2 it comes 1 foot long by 40 inches wide. It costs 11.40 per foot. It is an acrylic coated silicate – its temperature rating is 3000 degrees. You use RUTLAND stove cement to hold the burner mat to the combustion pot floor. The burner mat is narrower on one side than the other. The wider part goes towards the left. That U shaped metal piece inside is riveted to the base. It has a screen on it with three holes through the metal piece. Kerosene works its way through these holes to the igniter. The new burner mat has a rectangular cutout that goes around this U shaped channel – it slides underneath the igniter tube and fuel tube. It is held to the pot floor by five applications of stove cement four corners and a long strip of it on the left middle near the edge.
The flamerod works like this:
At rest with the heater on, there is an AC voltage applied to the rod the voltage is approximately 140 volts. When there is a flame around the rod, the air is ionized and conducts electrons. The voltage polarity changes to DC. This DC signal is applied to the computer board. As long as there is a DC voltage here, the unit stays running. No flame the unit will lock out after 300 seconds. It reads the DC through the flame to the pot ground – metal. If the flamerod is bent so it touches the combustion ring it will lockout the heater. If there is sufficient soot that covers the flamerod and the porcelain tube – the heater will lockout. A chip of soot against the flamerod and pot side will lockout the unit. With the flamerod fastened to the pot it should be approx center between the pot side and combustion ring. It is made of hard metal and don’t bend easily. You can vary its position by loosening the top screw and tightening the bottom screw – this will move the rod tip towards the combustion ring. Loosen the bottom and tighten the top and you move the rod closer to the pot side.
The viewing window is a mica glass or quartz composition. It breaks easily. A replacement glass, once again from McMaster-Carr is BORO-SILICATE glass. It has a temperature rating of 600 degree plus.
Thanks for the description of how the flame rod detects the presence of a flame. I expected a optical detection like an oil burner cad cell. Do you know how much time the computer board allows before it expects to see a DC voltage at the flame rod. I would like to get a 441 service manual, do you have one in a PDF or other format.
flame detect is 300 seconds before lockout. elsewhere in this forum is a downloadable pdf file which encompasses four monitor heaters. the troubleshooting flow chart applies to most monitor heaters regardless of model or age of the unit.
HI thanks for that post its very helpful, sorry to post on old post but this is my heater to a tee and i knew al luce (RIP) so it's ironic, he put a heater in once worked horribly!! haha anyways I'm now dealing with a MPI monitor 41 (oil outside) and both of them worked okay last winter they were both cleaned by oil company year ago, this year they keep shutting down and flashing all burner lights, if i keep restarting sometimes they'll catch and run but last few days they start up, get to 50% of the burner lights and then they switch off and flash no heat... any help would be much appreciated thanks!!
within this same thread there is a part two. you should read that.
you say you have an outside tank. where you are at do you have below freezing temperatures? if so, remove the inline filter assembly and go straight to your heater inlet line. water will freeze inside the filter pot and then nothing will work. in the 41 look on the side of the heater and you'll see a large phillips screw and two smaller ones. make a trough out of tin foil and use a shallow pie pan. put the trough in and around the casting where the screws(s) are. unplug the heater. shut off the fuel from the outside. unscrew the large screw a few turns. examine what comes out of the sump. if you are using dyed k-1, you'll see some brownish crap with the oil and maybe clear liquid [which is water]
unscrew the other two screws, remove the plate and gasket and remove the inner screen and clean it with gumout. replace the screen and plate with the rubber gasket. tighten the large screw and re-establish fuel flow. plug in the heater and turn on. the heater will go through a purge cycle, then if everything has been proved, the ignitor will turn on and the solenoid pump will prime and the heater will attempt to start.
hayzee your posts are amazing, very accurate and very helpful thanks again!! i tried like you said in your last post, i replaced the filter outside, drained the unit and cleaned the filter, checked the flue for junk and checked all my turn off valves, i've try'd many times to restart with and without priming, the only difference now from before is the burner status reaches 50% like before then goes to 0, after about a min (just fan running) it begins to flash, were before it was flashing immediately after running at 50% for about 45 seconds, also all the burner lights are flashing like before but now instead of 00:00 it flashes the temps (set and current), also i can see a small blue flame inside the chamber when the status lights are 50%, it makes a sound i havent heard right before it lights it sounds like a grill when its lit, so that means its getting oil right? any other pointers would be much appreciated you guys rock THANKS!!!
actually the temp lights are not flashing its just the burner status lights, so cleaning it did something (u da man), i have always kinda had to keep rebooting if i run out of oil, eventually it would catch and run fine, now just cant get past that 50%..
Bleed the air off the top of the filter. If you have a Goldenrod filter, remove the copper fuel line fitting at the filter. Open the valve and catch the fuel that comes out. It may take a second or two to flow freely. If you have a General filter, take the small bleed bolt out of the top of the filter case. Open the valve, the fuel should shoot up 6 or more inches. This is the time to check and make sure the General Filter is installed correctly. The IN port should be on the tank side and the OUT should be on the house side. It is a cleaner job to bleed the fuel outside.
k so like i mentioned before i have two of there in the house (monitor 41) and the one in the basement working on gravity is going for now full blast, the main one working with tomitomi pump (one i've been toying with) starts to warm and is now flashing the 50% burner lights on then off 3 or so times in a row.. then nothing then flashing... going to try to bleed the air in filter outside like u mentioned THANKS!!
Last edited by chroniclivin; 01-07-2012 at 04:32 PM. Reason: added
I'm new here and am not sure if I should have started a new thread or jump right in here, sorry if I did it wrong. I have a Monitor 2400 and I believe my igniter is bad. The reason I think this is because I tested the voltage on the circuit board where the igniter connects and I get 120 VAC. When I ohm the igniter it reads open even on my meter's highest ohm setting. Thank you for your help.
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