Harman P68 Stopped Christmas Eve at 8:15 PM Three Blinks

My pellet stove is dead right now. The three blinks of the status light I guess mean that no
communications with the Exhaust Sensor Probe. I will order some new ESP's and first replace the
ESP. Today, I will do a thorough cleaning of the stove. And look for ESP's on Ebay from a
quality source.
My P68 has red wires to the ESP. I understand that there are two types of ESP's. Some
with red wires, some with black wires.

I am running the oil boiler for now.

 

Ouch.....

 

I am ordering some new ESP's to stock. The old ESP that I removed and that I think has failed,
has a measured resistance of about 1040 ohm. Does anybody know the measured resistance
of a new ESP?

 

Read on another forum that the red wire ESP he had read 1.1k ohms @70 degreesF. If you get another red wire one you should be OK, black wire ones dip switch 5 on the board needs to be OFF for black wire, ON for red. Hopefully it's just a flaky ESP and not a board issue.

sam

 

3 flash on status light does indeed indicate bad sensor probe. New one should fix problem.

 

Yes, I am going to replace the ESP sensor first, since that is the cheaper replacement. If that does not solve the problem,
then I guess I will be looking at the board.

After the stove stopped feeding pellets, and the three blinks were displayed,
I power cycled the stove a few times and tried to re-lite it. I add pellets and lite a fire with a propane torch.
With the fire I started, the auger pellet feed never starts and the stove never enters the steady state of a fire in the burn pot. After about
ten minutes, all the pellets are burned up and the fire goes out.
The other lights seem to display, which tends to imply that the control board is working.

 

I cleaned the stove real well, including the exhaust pipe on Christmas day. I put a long
brush down the exhaust pipe to reach the ESP, gently. On Monday, after reading more
on the Internet, I took out the ESP and rubbed the surface to almost shiny using only a
plastic type Billo pad, so as not to leave scratches in the surface of the ESP.
While the stove was down, I removed the rest of the skirts from the rear of the stove
and stored them. I plan to leave all of the skirts off so that I can regularly lubricate
motor bearings. While the stove was down, I learned how to carefully remove the control
board, removed the plastic and metal covers from over the red switch 2, and wrote down
all information about the control board. I plan to stock a spare control board.

The ESP resistance measured 1040 ohms which told me that it might be fine.

Upon putting the shiny ESP back in, I was able to start the stove, maintain a fire, and
regularly feed pellets. I guess the morrow of the story is that a clean ESP is crucial.

Does anyone know the resistance measurements of a failed ESP? Does the
ESP short-out, i.e. zero resistance, or become an open circuit, i.e. infinite resistance?

I would think that as the red wire ESP heats-up, that the resistance increases, i.e. a
greater voltage drop across the ESP. Is that correct?

 

Got this from a Mt Bob post on the other forum:

"there are no specs and charts,and you would have to test it over a wide temperature change, most people would just replace it as part of the diagnosis.But if you want to read an older post about them--
harman temp probes. red ones are between 1,000 to 1,100 ohms of resistance depending on what your room temp is (remember if the stove has been off for a while the probe may be much colder from the cold air outside coming through the OAK. All other ESP probes that are NOT red should read around 650,000 to 550,000 ohms resistance. After taking a good initial read you can breath on them or use any heat source and the resistance should lower as the probe heats up except the red which should rise."

About a year ago with supply chain issues I decided to get the complete repair kit for our P43 while they were in stock at Stove & Grill Parts For Less. Glad I bought then cause the price is now $100 more. Didn't notice at the time but it comes with both a red wire and a black wire ESP. I took my ESP out and shined it up last year for the first time. gets vacuumed and gently brushed when I do it's monthly cleaning anyway.
Here's a link to the P68 kit
Harman Pellet Stove Emergency Repair Kit With Control Board: 1-00-05886

sam

 

Hi Sam,
Thank you for the information. The emergency repair kit sounds like a good thing to stock.
I might try to purchase an emergency kit next June to July, when I hope the price is lower.

I really missed the pellet stove for the two days that it was down. While running on the oil
boiler, I had to keep temperatures in the low 60's, because it would be so expensive, $800
to $900, to re-fill the oil tank. I have now resolved to give the pellet stove attention and care
that "she so deserves."

To come in from outdoors, walk into a kitchen that is 70* to 75*, and see the fire in the window
of the pellet stove is so uplifting Maybe something to do with the caveman instinct.
Orson

 

Know what you mean. I go out and put out seed & mealworms ( we have a LOT of bluebirds coming daily) every morning and this past week with it in the low teens every morning, walking back in to that wall of warm air always gives me that "aahhh" feeling.

sam

 

Just found my receipt, it was only in Oct 2021 that I got the kit. It was $499 plus I got a double paddle fan blade (cause I read most folks have to cut the shaft to get the combustion motor off and no guarantee the fan blade comes off the shaft) for $15. Maybe in 2023 I'll buy the distribution fan, it's currently $180.

sam