Monitor 441 Heater

hollow i hope i am in the wright place i have a 422 and here is my problem i turn on the unit it comes on and runs for a little them all the lights start to blink so i shut it off and restart it and it does the same thing this happens 2 to 3 times 4 time is a charm then it will run fine for a day or 2 then it starts all over again any ideals i am at a loss the unit is about 5 to 6 years old

[HayZee518]

Monitor 2400 Heater

I finally got a look inside a Monitor 2400. Mine kept on giving me an E-14 readout. The prepurge came on, I had ignition, but when the heater kicked into high, I got flame out and the heater would shut down and lockout.
I found that the fuel line had a water-ice blockage somewhere in the inlet line. Once this was cleared up the heater would run and run.
The front cover is removed by taking out two screw on the side(s) lower. Then by removing three screw on both sides and one screw right in the middle of the louver assembly comes out.
The combustion pot is the same, the flame rod is the same, the solenoid pump is the same exceot that it plugs directly into the computer board. The air proving switch is the same. The fuel sump is smaller and doesn't have an adjustment for the float. The float is plastic and pivots in a plastic holder. The float looks just like one used in a garden tractor. At one end of the float is a piece of metal. This metal piece contacts a magnet should the fuel level get too high in the sump. It is reset by using a lever attached to a button for the user. The combustion blower is the same I couldn't see the damper but there isn't the omlnous click when the heater clicks into high heat.

[MEWelding.com]

here's a site that explains the temperatur thermistor. maybe you can get something from here:
Thermistor Temperature Sensors, Temperature Sensor Probes, PTC and NTC Thermistors.

That is a good reference. Thank you.

Update: Got a suitable NTC thermistor from Mouser Electronics for 69 cents. It works perfectly. Probably better quality than the original part for $43. Thanks again.

[HayZee518]

here's a site that explains the temperatur thermistor. maybe you can get something from here:
Thermistor Temperature Sensors, Temperature Sensor Probes, PTC and NTC Thermistors.

[MEWelding.com]

11620 ohms at room temp ofapprox 70 degrees. get one with resistance that goes down with temp drop. mouser electronics has one that goes for about 75 cents.

Excellent. I'm at their site now, thermistor. It looks like they have 3,199 different types of them. Which would be the right one to get? Filter the ones up to 20 k ohms? The manual states a voltage of 1.6 - 3.3 DC for the M41 taken @ Q on the PCB and 5v with the sensor disconnected. Not getting any matches up to 33 K ohms with up to 12v.

Thank you.

[HayZee518]

11620 ohms at room temp ofapprox 70 degrees. get one with resistance that goes down with temp drop. mouser electronics has one that goes for about 75 cents.

[MEWelding.com]

Thermistor ohms at room temp?..

Anyone know the resistance / ohms of the thermistor at a particular temperature, say 72 degree F or in that range? It would be great to get the appropriate thermistor with having to pay $43 for it.

Thank you.

[HayZee518]

go get it and d/l it yourself from the thread. it is much too large to send through email server. - hayzee

[grasshopper]

Hayzee or Rob,

I'd also appreciate that pdf sent to bob@hotspas.com so I can restart my heater which worked fine last spring but will not startup (fan) this fall/winter, Thanks!

[cbfiv]

thanks!

line inside chamber was clogged and feed line from pump. all cleared and warm. just in time for the wife's arrival! thanks to all for being here

[adnadeau]

The link to the service manual is at The DEFINATIVE Monitor Thread post #9. You could also try disconnecting the tube from the solenoid pump
from the combustion chamber connection, sticking the free end in a tin can,
and turning on the Monitor. See if kerosene comes out of the tube from the
pump. That would narrow it down to the line inside the chamber.

[HayZee518]

if the solenoid pump is working then the line feeding kero to the chamber must be plugged. get about a three foot piece of 18 ga copper wire and run it through the entire length of the fuel tube. sometimes the fuel tube right at the igniter gets clogged with carbon.

[cbfiv]

Oh yah- last nt. I found the short tube in the combustion chamber that the fuel supply is connected to was blocked with carbon build up. After cleaning it out the unit lit and worked for a few minutes then shut off. After that is when I tracked the fuel supply, or lack of, back to my previous post. Thanks

[cbfiv]

I'm not getting fuel into combustion chamber. It is supplied to the small internal tank, full to the line. The solenoid pump and the solenoid controller both work, I know this as I swapped both out with my other heater one at a time. The other heater still works fine. So it seems to me that it might be before the solenoid controller.? If so would this mean by board is bad? I hear they are no longer available. Also, I can't find the pdf for the manual, any help?

[adnadeau]

If you haven't already, download the pdf service manual as posted in one of these Monitor threads. Use the troubleshooting flow charts. Troubleshoot as you would a car: it it getting fuel and/or spark (igniter)? Is the combustion air blower coming on? Does the air pressure switch close? You need to know how to use a multimeter to measure resistances & voltages. Attached is an enlarged copy of the 441 timing chart from the manual showing the sequence of events on startup. Try to determine which event is not happening.