Monitor 441 Heater

[cbfiv]

help

I have 2 monitor 41's and a lifter pump in the system. I just returned home after months and turned on the heat for the first time since spring. One heater and the pump work fine. The other one gives the same problem evryone else lists. I read all the posts and followed all the instructions, cleaning the fuel strainer - it looked fine anyway, opened the the burner chamber & vacumed everything and wiped the rod - things didn't look so bad in there either. The solenoid pump feels like it is working. I hate calling for service as it is very expensive here and they can not get over for weeks. On top of it all, my wife will be home in a couple of days. Good thing I came early to open the house. Any and all help is greatly apretiated. Chuck

[HayZee518]

if its computer board related I can't help you. all the resistors are quarter watt rated. the control circuit is 24 volts and 5 volts dc. there are four diodes used for the 5 volts and a bridge rectifier for the 24 vdc. the board uses 120 volts, 24 vdc and 5 vdc on it. the ICs are all soldered in - no sockets. TRISTAN is the manufacturer for the solenoid pump and its matched controller.

[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.

[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?

[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

[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.

[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.

[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

[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!

[HayZee518]

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

[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]

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]

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]

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]

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.