PF100 6 blink

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New Member
Feb 19, 2022
Thank you in advance for this forum. I have been reading and learning an awful lot on here lately. I recently purchased a Harman PF100 furnace to replace a wood stove in my pole barn. The previous owner had used it for years, had an issue with poor combustion and replaced it with a propane furnace. I took the gamble hoping I could get it to work.
I have replaced the burn pot, the gasket at the burn pot, the insulator and the esp probe (red wire). The furnace starts easily, and burns great for about 45 minutes, then I get 6 blinks and shuts down. I can immediately get it to restart, but it will only run 30-45 minutes at a time. I am never losing flame, so I do not believe this is a pellet feed issue (the pot is still full when it shuts down and the flame looks the same).
I have what I believe is decent flame, it appears to come out at about a 45 degree angle and seems to warm nicely when it is running. I have the distribution fan set to the slowest speed and it stays on, if I go to the middle speed it does cycle occasionally.
I cleaned the draft fan decently, but I can't get it perfectly clean. The surface in the flue area is very shiny and sticky, I tried to chip it away to clean it out the best that I could. I am not getting any new creosote (the probe is staying clean) but the previous owner's poor combustion I am sure contributed to what I am seeing. I did clean a bunch from the inside of the furnace.
When the furnace does shut down, the draft fan never stops.

Any help or advice is greatly appreciated.



Minister of Fire
Dec 19, 2009
Eastern Ontario
From the Manual
A 6 blink status may be caused by several things: 1. Blocked or partially blocked flue. 2. Blocked or partially blocked inlet air. a. Backdraft damper on the inlet pipe may be stuck closed. b. If outside air is installed, the Termination Cap may be blocked. 3. The air chamber under the burnpot may be filled with fines and small bits of ash. 4. The holes in the burnpot may be getting filled with ash or carbon buildup. 5. Combustion blower fan blades may need cleaned. 6. There is no fuel in the hopper

The manual


Feeling the Heat
Apr 27, 2012
Southeast Wisconsin
I think I recall someone having a similar problem finding that the distribution blower control was mounted improperly on the output plenum. It got too hot and the limit switch in the control unit shut the furnace down. A defective limit switch, perhaps? I don't know why you'd get an error light, though.

My boiler blinks 7 times to signal it had overheated.


New Member
Feb 19, 2022
Thank you for the quick replies. I decided to dig into the combustion fan again. After some research, I discovered the creosote was much thicker than I first thought. I grabbed a torch and started heating and scraping the area around the exhaust fan, up to the flue. Once I had this area cleaned out, I reassembled and gave it a shot. The fire burned for 2 plus hours without stop this time. I decided to shut the stove down and call it a night, but I am hopeful that I have found a solution.

Thanks again!
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