Harman Advance Room Tstat Man Mode Running Hotter than Setting

[forjack842]

First Off, Outstanding Forum!! My first place to go and is a fantastic source.
Have an Advance with ESP Black wires) about 20 yrs old. Has been unbelievably reliable.
My setup is I run the stove with Auto/Man in Manual, Wall Tstat in series with temp sensor.
Honeywell setup as described here and at Harman. Temp set at 75 all day/night.
Completely cleaned Jan 25.
Issue: The stove has kept the room temp at 75 +- 1 degree for years. Last week the room temp has climbed to 83, pellet feed seems to be a consistent amount keeping the pot pretty full and flame higher with the 4 LED Flash requesting "Keep Alive Idle" . The stove body temp is actually keeping the room hot without the distribution fan running. So with the LED flashing 4 times indicating Tstat circuit is "Open" the stove still runs as if the circuit was needing heat but the distribution fan does not run.
Moving the Auto/Man switch to Auto and the Tstat at temp, 4 LED flash, the stove pellet feed stops and shuts down as it should, then refilling and igniting when the 4 LED flash goes solid.
I'm wondering if the ESP is become inaccurate. I cant find any other reason.

A bit more visual, while in 4 LED Idle, the pellet feed does 3-5 feeds in about a minute ramping the flame up to typical catch up but with no dist fan run then stops till the pellets burn down into the burn pot bottom then starts a repeated pellet feed of 3-4 again. The "Feed Adjust" set between 1 and 4 doesnt appear to change feed rate. Has very good flame shape and draft. I ran the stove in Auto last night and room temp was 75 this morning.
Any thoughts please,
Thanks Jack

 

[Mt Bob]

I would replace the exhaust probe, and clean the pots.

 

[jackman]

I agree with Mt Bob. That would be a good place to start. I'd also suspect the TStat wired in series. I'd remove it and try the stove in Room Temp mode to see how it behaves. I'd also run a self test to see if that shows anything.

 

[forjack842]

Evening and thanks for your replies. Pots were cleaned on Jan 25 which is when I do a full mid winter clean.
I am a bit "jargon" confused. I run in what I thought was "Room Temp", the "Stove Mode/Room Temp" control pot is always in "Room Temp High", with remote Tstat opening and closing Temp Sensor Thermistor circuit. I can switch between "Auto" and "Manual" via the toggle switch. My stove in "Auto" will start and gracefully shut down on the demand for heat from the Room Temp Thermistor. In "Manual" the stove will initially start and then gradually cycle the flame by amount of feed from high flame to "Keep Alive" on the demand of the Room Temp Sensor. The recent issue is the "Manual" mode appears to cycle Idle to Full Flame and back to Idle regardless of "Room Temp Sensor" demand. However in Auto mode it preforms as it should starting and gracefully shutting down.I've got a ESP sensor order arriving Monday

 

[forjack842]

Update and Fix:
First I removed the control board and replaced the 1000us/25v capacitor. I did this because I was getting random motor buzz on the Combustion fan and the LED s were not as bright as they use to be and thirdly the stove was built in 2001 and these caps dry out and lose value. Repowered and the IDLE burn in MANUAL was much less , but not yet correct. Replaced ESP, dated 2001, . Idle burn now back in the burn pot throat where it should be. Also Low Draft control was back to its full range with control centered as I originally got it. I now understand more on the interplay of the ESP. As this sensor ages the IDLE burn increases to satisfy the control boards required temp in the exhaust to allow just enough pellet feed to keep the burn alive without wasting fuel. Also the ESP had a brown coating, thin like a paint, so the true exhaust temp would be incorrect. A knife and steel wire brush returned the shine but I put in a new one anyway. Old one goes into spares package.
To recap, I had a remote thermostat temp set for 75 degrees, before repairs, the room would heat to 81 with the status LED opening Room temp sensor circuit, no heat demand and dist blower off and the burn pot flame cycling from IDLE to decent flame over 5 minute s. The stove was radiating not blowing heat. Now pellet feed is a constant 60 seconds between LED illumination. The duration of illumination is the amount of pellets fed into the burnpot by the auger. In its "like new" with capacitor replaced and new ESP in IDLE /MANUAL the burn is barely noticeable , and deep in the burnpot. This is exactly as it should be