Harman P68 Distribution Fan ESP concerns

I just joined the group after spending hours looking at the great info being shared by everyone. I have installed a used Harman P68 (S/N 009255) from a gentleman who said he bought it new in 2008. A little background on the unit. The previous owner claims he loved the unit and had the control board and igniter changed Dec. 2014 but needed to get rid of it because his elderly uncle couldn't carry pellet bags anymore and replaced it with a propane unit.

After reading manuals and threads I ordered a new "Black" ESP probe yesterday after thinking that is what I need to fix the problem I'm experiencing and looking for confirmation or pointed in a different direction.

In test mode after first firing up the unit all lights and functions work. Distribution Fan blowing fine, Combustion Fan blowing fine, Feed Motor fine, Igniter fine. Once the 1st time start up process was followed and I switched to Room Temp, Auto Igniter, an 80 degree setting and 4 on the pellet feed dial the Distribution fan never again came on regardless of how long it ran after I changed all the settings from Room Temp to Stove Temp, auto ignite to manual, feed rate from 4-6 and back again. Eventually it gave a 5 blink error code but since the igniter lit the fire it couldn't have been the "suggested" problem.

Did I do the right thing by thinking the ESP isn't sensing the exhaust temps and controlling the feed and burn rates?

2nd question: Does my pellet feed box require a lid switch. Mine doesn't have one but I see that part offered.

alternativeheat said:

I'm questioning exactly what modes you were in here. For instance in Stove temp mode with an output set at 4 or lower you won't get a distribution blower on later model units. And your control board has been changed, just a guess but my bet is it has the later control board.

If your stove sensed a misfire by timing out before a flame established that could set the code.

Just For For The Record, we have had people think they were in one mode and actually in another, So :

Room temp is with the dial in the up position for the distribution fan. With the dial turned to the down position is Stove Temp Mode.

The feed rate set to 4 is fine to start with.

I suggest maybe shut down the stove. Unplug and relight it in the mode you want to run in. Obviously start it with the igniter on. Igniter on is Auto. Igniter Off is Manual.

Is the stove running now ?

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Thanks for your Reply!

I used the the procedure for "Starting First Fire". Igniter switch to Auto (up position)
1 Turn mode selector to OFF
2 Fill hopper with pellets
3 Clean burn pot
4 If starting after an empty hopper, turn Feed Adjuster to "TEST for one 60 second cycle (I DID THIS AND IN TEST MODE ALL THE FANS RAN FINE)
5 Turn Feed Adjuster to #4
6 Igniter switch in Auto
7 Turn the Temperature Dial to desired room temp. (I SET IT AT 80 TO TO HAVE IT ABOVE THE #5)
8 Turn Mode Selector to Room Temperature or Stove Temp (I SET IT ON ROOM TEMP)

After going through this pocedure everything was going as i expected and once the pellets moved far enough out on the burn pot they lit just fine and the fire appeared to burn normally for a while. Waiting for it to warm enough the Distribution Fan never came on while the Combustion Fan, the Feed Motor and Igniter appeared to work fine. It ran like this for a long time and the flue pipe started to get very hot and the Distribution Fan wouldn't come on no mater was setting I put it at on the L to H portion of the Room Temp setting. I tried the same in Stove Temp mode thinkig maybe the Room Sensor wasn't working properly. Same problem. The Distribution Fan didn't run although it ran fine in "TEST" mode while trying to get first load of pellets to the burn pot.

alternativeheat said:

Ok,did the flame ever trim back or ever increase and decrease in intensity ? If it did that I would not suspect the ESP immediately.

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When the distribution fan never came on I increased the pellet feed rate to the highest setting, I increased the room temp setting to the highest setting thinking that maybe the ESP wasn't reading the temps properly and tried to get it to come on because it sensed we were way low on heat in the room based on the Room Temp setting and what the Room Sensor might be reading. I did the same thing later that evening in Stove Temp Mode when the Distribution Fan didn't come on even with stove exterior giving off lots of "radiant" heat from the fire burning with the actual room temp being about 68 degrees. I figured on the Stove Temp Mode setting I would be eliminating the "Room Sensor" from the trouble shooting equation. When I shut the unit down for the evening I moved the Mode setting to OFF. The auger stopped feeding but the combustion fan kept running while the fire burned out. The Distributon Fan never came on during shutdown although the Combustion Fan kept running until the fire was out completely. I suspected the Combustion Fan would run until the ESP detected a safe temp to shut off the combustion fan. When the fan ran over an hour and the stove and vent pipe were cold to the touch I had to pull the plug from the surge protected power outlet to shut if off. When I had turne all the feed rate and temp settings to their highest setting in both Room and Stove Temp modes it did throw the 5 Blink error. There is no problem with the "Igniter" lighting the fire when I tried starting it in Auto Mode Twice.
I put 2 day shipping on the black wired ESP I ordered online which should have it here Tuesday or Wednesday since I live in "Way Out Here" Western Wyoming where my closest Certified Harman Dealer is 125 miles away in Riverton and a five hour drive from where we live. The two local "Pellet Stove" stores where of no assistance as I asked some of the similar questions discussed here and they had no idea how Harman stoves work or their components.
If the Black Wired ESP fixes the problem I will be ordering a backup ESP and have seen posts that the Red Wired ESP is for the newer P68 stoves and if you have an older unit the Red Wired ESP works if you change the Dip Switch setting for switch #5 from OFF to ON.
Today I pulled the ESP out to check it. It wasn't coated with anything except a little soot which came off with a paper towel. I put it back in and tried again. Same results. No Distribution Fan running except in TEST Mode
I hope I'm not going into Data Overload.
Thanks for your input.

miteclipse said:

Maybe the new control board is set to have the "newer" esp probe but the stove has the original esp. You could try to change the dip switch on the board to off or on.

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Current Dip Switch Settings: 1 on, 2 on, 3 off, 4 off, 5 off, 6 on, 7 on, 8 on. Since I have the older black wired ESP everything I have read says the control board dip switch should be set to off. If one has the Red wired ESP the #5 dip switch should be set to ON. I thought about trying to change the #5 dip switch setting and try it again but I was concerned that "might" create some other problem. Electronic circuitry can be sensitive and I'm not confident to make too many changes without more specific info that I won't "break" something that wasn't broken by trying too many things. The circuit board number is B5371A Handwritten in black magic marker on the front of the board in a couple different spots is "T87", "A16", "1194". I suspect these might be version numbers or features. I couldn't find any info on these markings. On a small white label on the board is printed "F5371 AC / E" and "GEC 121400344". I have added this data in case someone who is very familiar with this unit might shed some light on the Controller Board.

miteclipse said:

on my p68, the distribution fan comes on after it lights, so my combustion/distribution fan buttons are light on the control board. is your distribution fan light on the control board or is it not?

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I've tried to attach a few photos of the fire that started automatically in Auto igniter and the settings on the controls. I included a photo of the dip switches which are correct to everything I've read. When I pulled the "Black wired ESP" out to look at it closely I noticed is was slightly bent towards the rear of the exhaust vent. I've read that they are very sensitive and the way they work with the controller board is through heat generated "resistance" which related to a specific temperature and controls the functions of the unit. The third photo shows that when the unit was burning fine and for quite some time the "Distribution Blower" never came on. The Distribution Blower does come on when in TEST mode. I'm expecting the new ESP to arrive on Tuesday or Wednesday and I will report on whether that addresses and fixes the problem I have reported. I looked into the Diagnostic Tool but that is over $400 so it doesn't make financial sense to get that unless I decide to become a Certified Harman Technician in this area. (Just Joking)

Harman Lover 007 said:

If the picture of the CB just below the dip switch pic was taken when you had that much fire in the stove, I'd say you are on the right track with the ESP. The igniter should be off by then and it isn't and the Dist blower isn't running. Let us know how you make out with the ESP.

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As much time as I have spent investigating this problem my wife says I now have a PHD in Harman P68 operation. (<; I need to understand how things work so I don't become frustrated when "stuff" happens. Thanks to everyone who chimed in on this issue. If the ESP solves the problem I suggest to Harman that they add a message to the 5 Blink error about the Igniter not operating for NNN minutes that it can also be caused by an ESP not sensing the temperature.
Harman Lover 007....... The lights on the CB were while the stove was lit as shown in that photo. I actually recreated this same condition a couple of times as I shut down the stove, pulled the power plug to "reset" the CB as suggested on different error codes and restarted. I am betting time and money for the ESP that IT is the problem.

alternativeheat said:

I'm going to say if the ESP is bent it's all done ( ruined) !! When you get the new one in , post back and we all can go from there.

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Alternativeheat, I will close out this thread with whatever resolves the problem and a big Thanks for everyone who tried to add their knowledge to my data bank. This site is great.

Rockin C&M Wyoming said:

Alternativeheat, I will close out this thread with whatever resolves the problem and a big Thanks for everyone who tried to add their knowledge to my data bank. This site is great.

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For all those wondering: Part of the problem was the ESP but not everything. With everything cleaned out and ready to start again after installing the new black wire ESP I put it in TEST mode to see if all the functions worked. As before everything said OK in TEST mode. Once the minute Test Mode was over for all the fans and the feeder I put it in Room Temp mode and let it auto start. The feeder ran, the combustion fan ran and the igniter ran while the distribution fan was off. It took a couple of minutes for the flames to start and after a little warm up time with a really nice big flame the Distribution Fan kicked on automatically. Slow at first and then faster. After running about 15 minutes I checked the indicator lights and it was showing a three blink error code which is ESP failure requiring a RESET according to the manual. I turned the mode control to off and once everything had stopped, about 15 seconds I unplugged it for 5 seconds and then plugged it in again. The status light was steady on and everything was running fine again with the combustion fan, the distribution fan and feed light all working as one would expect with the feeder set on 4 running for about 40 seconds. After it ran for about another 10 minutes it threw another 3 blink error. The distribution fan cycles from low speed to high speed and then back to low again. After resetting it twice to turn off the 3 blink error I tried it in Stove Temp Mode, not Room Temp Mode. Same condition. It ran for a lilttle while and then threw the 3 blink code again. Other than the stove Distribution Fan going from slow speed to higher speed without any change to the knob while the fire remains relatively low and the feeder doesn't run for the 40 seconds once the error code appears. I am a loss again.
Anyone have an idea. 3 Blink Error Code in both Room Temp and Stove Temp mode with Igniter in Auto. The new ESP took care of the Distribution Fan running when it wouldn't before but now with the high speed low speed cycling of the Distribution Fan says something isn't right with temp sensing and speed control of fan. HELP............

mikesj said:

I think you may have a bad replacement esp. Very frustrating, but sometimes stuff like that happens. Buy another one and if it fixes the problem take the defective one back. If it turns out the esp isn't bad and something else is wrong you will have a back up.

I had a similar thing happen a few years ago- apparently Harman was supplied a bad batch of probes.

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When I felt I had exhausted all of the settings I could try to help diagnose what is wrong I set the Mode Knob on OFF to see what it would do. With the 3 Blink error continuing both the Combustion and Distribution fans kept running until the fire was out and the stove was starting to cool down at which time the Distribution Fan stopped while the combustion fan continued and then when it was really cooled down the combustion fan stopped. At that point the Power light was on and the Status light was still displaying the 3 Blink error. I unplugged the unit and quit for the evening.
MikeSJ I was planning on ordering a backup ESP since they appear to be the weak link in so many problems. I purchased this one at Mountain View hearth products. Do you or anyone else have a different vendor to purchase a backup ESP from?

miteclipse said:

I'm having a hard time finding your P68 model and current circuit board number from the earlier post.

Since it was bought in 2008, the serial number should be :
Pre 008281295 which would require the black ESP Probe, 3-20-11744

However, since a new board from 2014 was installed, that would make it :
Post 008281295 which would require the red ESP Probe, 3-20-00844

Someone else would also need to confirm if this is correct. If this is correct the circuit board dip switch #5 would need to be changed, or you would need the red esp.

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The part number on the ESP Package I received is P3-20-11744 as you stated. My Owners Manual (original one) shows the Thermister Probe (ESP) as PN 3-20-00744. Does anyone know the difference between the 11744 and the 00744? After having the stove off all night I fired it up this morning again and the same conditions happen. What I just got done watching and noting was the Feeder Motor runs for about 40 seconds (#4 setting) and then the Distribution Fan will go to high speed and run like that for a few minutes and then the Distribution Fan slows down and the Feeder Motor runs for a 4 or 5 second period. This longer feed motor run and the shorter feed motor run alternate back and forth over a few minutes with the Distribution Fan cycling between low and high speeds. During all of this the flame in the burn pot remains nominal the whole time due to a small volume of pellets. FYI. The Feeder Motor in this unit is marked as the 4 RPM model. I saw where there is also a 6 RPM model. I am so happy this Stove is auxillary heat for the house and the radiant in floor heat is keeping the wife warm and content.