Monitor 41 issue

[HayZee518]

on the back of all monitors including the propane ones, you'll see a white paired zip-lead that either goes directly into the heater or into a "molex" plug that can be unplugged. this device is what senses the temperature of the room and changes its resistance according to temperature. this changing resistance is sensed by the heater to start-up, maintain a steady temperature and/or shut down the heater as the room temperature reaches the set point setting. the wire is split in two inside the heater and plugs into the motherboard computer. removing the wires will default the heater to 42 degrees and the heater will not shut down, unless the unit has gone into lockout.

[dfitz3390]

no it closes thats why they call it normally open

[cadman44]

Ok, I will hit Radio Shack tomorrow after work.

I am good up until your last two sentences:

if you pull out the thermistor connector, the heater defaults to 42 degrees and stays lit. no need to set the setpoint to 90 degrees.

What is the thermistor connector?

[HayZee518]

sorry, E-14 is indicated on the 2400 vented heater. the older units used those orange burner lights according to burner status. eight flashing lights mean overheat or no flame and flame rod lockout in the main board. to check the flamerod circuitry get a diode and a 100K resistor. connect the diode and resistor in series. use some hookup wire and solder to the diode lead and resistor lead. when the heater is on with a flame, disconnect the flamerod wires and substitute the resistor/diode assembly in the jacks. if the polarity is correct the heater will shift into high heat and keep running. if it shuts down and goes into lockout, reverse the resistor/diode assembly and try again. now it should stay running. if you pull out the thermistor connector, the heater defaults to 42 degrees and stays lit. no need to set the setpoint to 90 degrees.

[cadman44]

Also, what is this e-14 error that I have seen throughout the forum? How do I tell if that is the error that I am getting?

[cadman44]

Ok, so I just bypassed the fan switch (the single one not the one in series on the right). I plugged the unit back in and the fan started right away. I turned on the unit and am still seeing the same problem. It goes through the start up routine (about 4-5 minutes), the heater turns on, and then after a couple of minutes, it shuts down with all eight bars blinking. Does that tell you anything?

[HayZee518]

the top one that's the fan control. the other two are connected in series and are the overheat stats.

[cadman44]

Looking from the front of the unit, there are two thermostats on the top right and one located more middle left.

The left one is the fan thermostat. The parts diagram I am looking at only has a leader to one of the adjacent ones on the top right and calls it the overheat thermostat. Which one should I jumper?

[cadman44]

Thanks again for all the help. I don't mind putting the time in and trying different things. I will check that when I get home from work tonight.

[HayZee518]

this seems like a raw way of troubleshooting but trial and error seems the way to go. after a while you'll get to know what's supposed to happen and when. for the main fan - it gets its signal from a plenum switch - I think its the top one which is normally open and closes when the plenum temperature warms up. for now jumper it out. it'll start as soon as the unit starts, so don't be alarmed. see if the heater goes to full heat and keeps on running. as long as it heats and runs - you could ascertain that the fan might be bad. e-14 would give you a lockout for overheat and shut down. remember to unplug the unit to reset the computer. merely shutting it off won't reset the computer.

[cadman44]

Ok, so I had the chance to look at it again last night. I did check the switch first. It works just as Hawkins said - normally open and top port for the hose. The switch is fine.

I did take the hose out and checked it closely for any holes/tears. I blocked one end with my finger and tried blowing air through it and there are no leaks at all.

I did take the fuel line from the pot and fed it into a cup. It does have fuel going to the pot.

I turned the unit on. It went through the startup cycle. The burner did turn on. I could see a flame (some orange) and it got warm. I will check for plugged holes tonight. I needed to let it cool down last night and it got too late. At this time, the displays shows 4 bars of the 8. After 5-6 minutes from when I turned it on it shuts down and goes to all 8 bars blinking.

The blower (lower left - looking at the unit from the back) turns on right away and I can feel it sucking air in. If I remember correctly, the fan (middle/right - looking at it from the back) didn't turn on at all. If the fan is bad, would that cause the unit to overheat and shut down?

[HayZee518]

So it DID close! Hawkins was saying that the switch is wired common to normally closed, which tells me it OPENS when energized. That's wrong. It's supposed to close completing that part of the initiate string.

[adnadeau]

Air pressure switch

I measured the pressure in the pressure switch tube with a homemade U-tube manometer. The switch closed around 0.5" of H20

[HayZee518]

hawkins, so with air on the diaphragm the switch is open? that don't make sense!

[hawkins111]

air safety switch

The air safety switch is a NO switch. The two outside prongs are used. The hose goes on the top hole.

Sorry for the confusion on my part. The switch does close during operation. The marking on the switch are NO, NC and C in that order. The wires go to the two outside prongs, NO and C.

Again sorry if I confused you.


Tom