Monitor 41 issue

[cadman44]

I woke up this morning with the lights blinking on the heater. I reset it and went to take a shower. When I got out, it was blinking again. I reset it one more time and it seems to be working fine. It has been working "correctly" for a few hours now. I understand "working" and "not working" but this intermittent working/not working is confusing me.

[cadman44]

So I went out for the evening with the heater working. I came home to it working as well. A little while later, it cycled on and off a few times 10-15 seconds apart and then shut down again with all eight bars blinking. It must have been working while I was gone because I don't believe that it would reset and restart by itself. It just happened right after I got home. Any thoughts on this?

[cadman44]

I ran the flame rod bypass test. The heater continued to run. So as was mentioned, I believe the flame rod circuit was working properly. As the heater was running, it had a couple orange flare-ups and then settled down. I let it run for a little while and it seemed to be running fine. Blue flame and all. I put it all back together and it seems to be fine now. Unless something acts up in the future, I think I am good to go. Thanks to everyone for all the help. Not only did I get the heater going, but I learned a lot about it as well.

[cadman44]

No problem. I will pick up a 1n4004. Radio Shack is on my way home. Is the resistor that I got going to work? Thanks for the quick response.

[HayZee518]

a zener might work, but its main function is that of a voltage regulator. a 1n4004 is what you want. zener diodes are rated by voltage. when a higher potential is placed across them, they lock the voltage to whatever they are rated at and give off the remainder as heat until their Vcc [or biasing voltage] is extremely over shot.

[adnadeau]

Diode

'Nother trip. You need a garden-variety silicon rectifier diode such as a 1N4004. Or, if you have any old electronic devices lying around such as a GFCI duplex outlet, you can look there for one.

[cadman44]

I stopped by Radio Shack last night. There were many different resistors and diodes. There were Zener diodes, rectifier diodes, and switching diodes all with different volt ratings. There were also different wattage ratings for the resistors. I made my "best guess" since they were pretty cheap. I got the 1/2 watt 100k-Ohm resitor and the 5.1V Zener diode. Did I get guess right or do I need to make another trip?

[hawkins111]

chamber overhaul

Cadman,

When you get the flame sensor by pass hooked up and you run the stove remember, you have not proved the flame sensor on the stove good or bad. What you have done is “by passed” the sensor on the stove. You have proved that the flame sensor has shut the stove down and the flame sensor portion of the main circuit board is working properly.
Now you have forced the stove to think it has a flame in the burner. If it does have a flame you will see it, if not you will notice that as well. The flame sensor on the stove is doing exactly what it was meant to do. When it does not sense a proper flame it shuts the stove down. As you stated in an earlier post, the flame was yellow. The flame sensor senses that and shuts the stove down. Since your stove is a M41 and you have used it for 7 years it is time for a combustion chamber overhaul. The good thing the by pass will do for you is prove the electrical system of the M41. Igniter, fuel pump, indicator circuit, blower assembly and circulating fan can all be checked with or without a flame in the stove. With all that checked you can now proceed with spending the time and money to overhaul the combustion chamber and feel the rest of the stove is good to go. If you can’t prove the electrical system and need to overhaul the chamber as well you are looking at a big bill on an older stove you can’t get some parts for.

Tom

[cadman44]

I have previously taken out the flame rod and checked for corrosion/carbon buildup. It seems ok. I will not be able to get back onto this until Saturday. I will do the bypass test this weekend and post my results.

[adnadeau]

441 Flame Detector Schematic

Here's the schematic of the 441 flame detector circuit.

[adnadeau]

I agree with Hayzee. Try the resistor-diode bypass just to confirm that the flame detector is not working. The rest of the circuit may be okay; the bypass will show that.
See if you can measure the 120VAC secondary of the pwr xfmr that feeds the flame detector circuit. One leg of that feeds out to the case of the 41 through the green "ground" wire that is under a screw head near the PWB. Also, if you haven't already done this, remove the 2 screws that hold the flame rod, remove it and check for corrosion etc. There are many other posts here with details on how to do this.

[HayZee518]

it wouldn't hurt to buy the resistor/diode combination, make it up and use it to troubleshoot your heater. the flamerod is nothing special, other than a piece of metal that doesn't melt in a flame, is insulated by a porcelain tube. in the presence of a flame it changes its electrical characteristics. The air which surrounds it, in a flame, is ionized, that means the air conducts electrons. it is a "PLASMA" effect. normally it has an AC potential on it but changes to DC in a flame. there's a whole website that explains it.

[cadman44]

Ok, I tested TP7 to EP. With no flame I had 0.03-0.04 VDC. With flame it climbed as far as 0.98 VDC but no higher. You mentioned that it should go to at least 1.2 VDC. What does this tell us? Is the flame rod bad?

Should I go through the exercise of getting a resistor and diode or does this tell us what we need to know?

[adnadeau]

Flame Sensor check

Another way to check flame sensor operation is to connect your VOM (3VDC scale) between test points EP and TP6 on the PWB. With no flame you should see 0VDC. As the unit fires up, the voltage should climb to at least 1.2VDC. Point EP(0V) is on the upper right corner of the board and is the common point for all the DC circuits.

Correction: In the Monitor 441 it's TP6; in the 41 it's TP7.

[cadman44]

Oh, that makes sense now. If I thought about it a little more I would have figured it out. I will try to check this tonight.