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422 yellow after Rebuild


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  • 422 yellow after Rebuild

    I have rebuilt about 12 heaters in the last few years, maybe more. a 2200, a 441, a laser 30, two 2400s and just did about five 422s in the last few months.

    I know fordman has two or more 422s

    The 422s have more yellow in the burn chamber, expecially when on high. One of the 422s the pot was brand new. My 2400 is perfect blue on low thru high. the last one I did I pulled the round damper donut out of the combustion fan inlet and it seemed to help. I have a suspicion that it's putting too much fuel in the burn pot at the high
    setting. I might play around with that VR adjustment on the motherboard. as long as I mark factory setting I figure I can't hurt anything. wiring diagram indicates that controls the rate of fuel pump pulsations.

    I know mainstream opinion will say don't mess with factory settings but if I can slightly reduce the fuel input to get a pretty blue flame can't see the harm

  • #2
    I have no suggestions but you might talk to hawkins111 before making any adjustments. My understanding is he had a business selling and servicing these heaters and may have other suggestions before changing factory settings.


    • #3
      You should calibrate the fuel flow on your heater before you go messing with the pump. Use a flame sensor bypass and a calibrated cup to see where you're at.

      The Air Damper should be marked 422 and have a S stamped on it, if using a Standard exhaust. This damper should be installed as it is part of the induction system and is different from M441 dampers. The blower puts out too much air and needs to be brought down to spec by this part.

      If there is still a problem with the air you have to use a manometer and adjust the Damper solenoid. This is a PIA process and very seldom has to be resorted to. Look at the set screws on the Damper Solenoid to see if they are still in the same place as set from the factory.

      All this above is predicated on using a standard Monitor flue pipe with either a Z pipe or bent elbow connecting the stove to the flue.

      Tom H


      • #4
        Excellent info Tom, thank you.

        The Damper says the full word STANDARD I believe. All the 442s I have worked on in these last few months have them installed in the plastic combustion fan shroud, retained by a small screw.

        I will look into checking fuel volume from the pump. I will ground the flame rod pin on the MoBo to the chassis. Book says .164Gal/hr so thats 1.0496Oz every 3 Mins. So will round it to an 1 ounce every 3 mins

        I did inspect the solenoid flap/spring. Its normally open and makes full travel. I also unplugged it when the heater was on high, no change in flame color. I wanted to check if the motherboard was incorrectly commanding the flap/door to close. And I checked resistance of the solenoid. I think it was 4400Ohms.

        The exhaust is a standard monitor wall flue.

        I might be worrying about nuthin.

        Dont want to mess with the manometer thing.

        Have you heard of anyone adjusting the VR adjustment?


        • #5
          The pulse rate of the solenoid pump is controlled by the microcomputer U1 through an optoisolator IC12 in the gate of SCR Q2. Not much you can do about it. The 50k pot VR adjusts the current through Q3 which triggers to release Q2 after it's been fired.


          • #6
            All Monitor 422 units have a small damper in the suction case that is held in by a screw. They all also have a second damper in the flex hose. It can be part # 6209 Air Damper S or Air Damper E for extended exhaust pipes. These dampers are specific for M422. Without the damper S or E depending, the flame will be a little high and yellow.

            I have never touched the VR for the fuel pump on a Monitor 422 or 441.



            • #7
              Thanks for both replies!

              I will verify that its got the correct dampers and not mess with the VR adjustment.

              All my 442s run the same (and actually pretty nice) so its probably normal.


              • #8
                What does the 50k VR adjust? Sounds like it might be shutting off the ignitor?


                • #9
                  Here's a detailed explanation of the solenoid pump operation.
                  Taisan Solenoid Pump
                  I had to zip it because of the forum file restrictions.


                  • #10
                    Thank you!!