Monitor 441 question

[jmas]

I have the MPI 441 that started acting up. I replaced the SS burner bowl (old one was warped), the burner mat, cleaned the burner chamber and sprayed with the desooter. Things worked great for about a month, but now it's tripping off again (all lights flashing). This happens during the cooling cycle, after the desired temperature has been reached, so it's not fuel. Basically, when I reset the 441, the burner starts normally and brings the room temperature up to the desired level. Then it goes through the cool down mode - reducing the burn level and once the last glow bar is unlit, there is a click and all lights start flashing, needing another reset. I checked the burn chamber and everything is clean in there and that little wire rod sensor is not touching the walls.
Any ideas?

Thanks in advance.

[HayZee518]

only thing that comes to mind is the air proving switch. the velocity of air between the bottom of the pot and the upper half may be too weak opening the air switch. try jumping out the switch and let the unit go through a complete cycle. Because the lockout condition occurs when, no fuel, no flame, heat overload trips.

[jmas]

By jumping out the air pressure switch, do you mean just disconnecting the plug in from the circuit board (connection J on page 59 of the service manual)?

[HayZee518]

the air pressure switch has two wires that go back to the motherboard. either pull the wires off the motherboard and apply a jumper to the board, or pull the wires off the air switch and jump them together.

[jmas]

I jumped the wires at the air switch and then again on the mother board. Both times the problem persists. Do you suspect the mother board is bad???

[HayZee518]

the flow chart troubleshooting says - failure of resistor R59. the only thing left it says is - replace the microprocessor.

[jmas]

How much do those run and are they "easy" to replace oneself with no special tools?

[HayZee518]

yes, plastic stand offs and just "plug n play."

[jmas]

Thanks HayZee I'll give that a try - any online retailers sell monitor parts, or only through local dealers?

[HayZee518]

I never seen any retailers - mpi has the market tied up by selling its parts through dealers or servicing dealers.