Harman Advance Manual Mode no keep alive burn

[forjack842]

Been troubleshooting this for a while now. I have my Advance setup with a remote thermostat switching the Harman thermistor in and out controlling room temp from about 15ft away, stove feed at 4, Room Temp at High, Temp Dial at 85, thermostat controls room temp at 75 +-1. . Been operating fine for 10 years plus now. Last couple weeks I've had to run in Auto mode because the keep alive burn dies out requiring the Auto mode be set to re- ignite the pellets. It appears the Augur Feed motor is not being powered but Feed LED is lighted, possibly due to low draft sensor switch being open. However switching to Auto and everything works fine. Since the Low Draft Switch is necessary in both Auto and Manual to enable the Feed motor and igniter I'm guessing the Draft switch is not seeing sufficient draft (vacuum) provided by the Combustion Fan in Manual Maintain mode.
Question... In Auto mode is the Combustion Fan speed faster RPMs than in Manual Maintenance mode? Example, In Manual, not providing heat, I see the Combustion motor running at reduced speed, LED Off, but sufficient to cause the Low Draft Enable that allows the control board to maintain the keep alive burn. I have the "Low Draft Setting" at its max increasing
TIA,
Jack

 

[Mt Bob]

Yes, the fan is probably at it's slowest in fire maintain mode. It also changes depending on stove settings, and probe readings. Anyway,I would jumper vac switch, and see if it stays running. Also make sure fan spins freely.

 

[forjack842]

Yes, the fan is probably at it's slowest in fire maintain mode. It also changes depending on stove settings, and probe readings. Anyway,I would jumper vac switch, and see if it stays running. Also make sure fan spins freely.

Hi Bob,
I have a new draft switch and have been holding off looking for any data on Combustion Fan speeds. I have a clip leads and was going to do that jumper as you said. Thought I bounce the symptoms off the forum before I do that just in case.
Thank You Sir!

 

[Mt Bob]

NP. Yes, many believe a Harman fan only runs at one speed. I'm sure you know to clean out the hose, and, because of age, clean out the nipple to the firebox. Although there have been cases of fan motors running slow because of control board. But you know the first steps.