I'm new here so excuse my lack of knowledge. A week ago my P38 suddenly began to feed too many pellets into the burn pot. It went for a short time unnoticed until I caught a whiff of smoke. Pellets poured over the burn pot into the ash pan where they continued to burn, I shut the system down and it cooled down normally and shut off in the proper manner. I performed a thorough cleaning in Oct, including gently cleaning the ESP. Last night it started to do the same thing and I had it set at #2, on the dial only this time I was right next to it. I noticed an odd faint plastic wire type smell leaned over to saw the auger was feeding pellets at a turbo pace, verified it was set on #2 this time I shut it down only it wouldn't shut down! I opened the hopper lid which stopped the feeding of pellets. Again the fans ran until it cooled down and shut off. I re-cleaned it today and it was clean. I turned it on and it started feeding pellets as if it was in turbo I wanted to turn the feed knob up and than back down but it made a loud electrical pop and filled the room with that funky smell. I unplugged the unit and here I am, I suspect I smoked the circuit board. What say you guy's.
Harman P38 Major Malfunction!!
- Thread starter Cold in W.I.
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GeHmTS
Feeling the Heat
I'd take a look at the board, see if any noticeable spots that look overheated or melted. Unplug it first.. The "pop" is not good.
should be easy to diagnose. Look over wiring good to find the short so if you do have to replace the board you dont fry the new one. Remember there is a fuse on the board, may have saved the board. If you do need a board you will get the upgraded board w/ 3 knobs and a room temp sensor. It is a ugrade kit that takes place of the 2 knob board.
I would think that for it to run the auger continuously something happened to the board (shorted) or control potentiometer for auger speed..
I'm about to start, had to finish my coffee first. Yea I've priced the circuit board as you mentioned at $329.00 free shipping. After reading many postings and given it's age I think I may want to check everything top to bottom. Recently to be honest I did hear that squeak sound as others mentioned. I suppose 8 years of use mechanical things do wear out.
My inspection of the wiring found no cuts or anything out of the usual. My inspection of the circuit board ( 03-20-03769) on the other hand revealed the fuse to be virtually intact, the board however shows 2 areas of damage. My digital camera doesn't do close up's well at all sorry about that. Area 1 looking down lower left area I found a resister labeled (R-7) smoked, I also found the larger black I don't know what it is damaged as well (Q-2). Anyone know what they control??
I just went and checked, the control potentiometer as you mentioned and that is directly next to and connected to the smoked resister (R-7) on the circuit board. It makes sense that knob was used the most. If that was the problem than when I turned it up and down yesterday and it was the problem I gave it the kiss of death. Would that also explain why the fuse didn't blow?
Possibly. The potentiometer, aka pot, may have shorted blowing some of the circuitry but not enough to overload the fuse. The pots Harman used are notoriously unreliable.
I would replace the whole board. Without a detailed schematic it may be impossible to do a thorough failure/stress analysis on the circuitry. You may end up replacing some, and not all of the failed components, and experience a new failure mode the next time power is applied.
GeHmTS
Feeling the Heat
If your stove is new enough, it may still be under warranty. You should try and understand root cause so that the incident doesn't happen again. I think that the more interesting question here that may help others.
Also if you replace the board make sure you have a good power surge protector, if you don't have one already
As stated earlier, I haven't had a single problem with it in 8 years. We have narrowed the cause down to the manual feed control knob the older 38's had. Can't say with 100% however with the symptoms that were #1 over feeding of pellets while set at number 2 of a possible 6, it was feeding as if it were in turbo mode. #2 the continuing of feeding of pellets even when the knob in question was turned down to the off position, the only way to stop it was to open the hopper lid effectively stopping the feeding and allowing the fire to burn down and evacuate the smoke. #3 the "Pop" I heard was only after I plugged the stove in the next day which in the off position started feeding in turbo mode and I attempted to turn the knob up to 5 and back down to off. This knob had constant use for 8 W.I. winters. #4 the circuit board showed damage only in the area of the knob and resister connecting to the knob. #5 the fact (albeit) the fuse never blew. I just now have to save my money and replace the board with the upgrade and purchase a new surge protector for additional safety old surge protector is 8 years old as well. Sadly my digital camera really bites with close up's not a single picture was clear.
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Yea, Gonna grab a new one, old one is 8 years old and at the cost of a new board $329.00 better safe than sorry.
You did good for 8 years. My controls on my P38 started acting up after 5 years so had them replaced. Also have a new board as backup..
I had to replace mine 2 yrs ago after approx. 8 yrs of use . I found a new two knob original for around $200 or so , but probably the last of em .
That doesn`t count the time I replaced the two pots in the first one. They only lasted a couple years.
That doesn`t count the time I replaced the two pots in the first one. They only lasted a couple years.
Alright here is the latest. While waiting for the new upgraded circuit board I cleaned the stove from A to Z. ESP sensor had minor ash on it and cleaned up easily. I installed the new board painfully slow following the instructions (lousy pictures). I set the dip switches for the blk esp (1-5 down 6 on 7down and 8 on). I turned it on and everything seems to work, problem is it's feeding as if it's set at a low setting no matter what setting I have no flashing lights yet it refuses to go into a higher feed rate. To be completely honest the instructions for the low pressure switch were at best sketchy the 2 posts on the instructions have me attaching the wire to it but wasn't specific which post, the other post goes to the auger motor. I'm wondering 1 did I wire it wrong and 2 could it still be the esp sensor even though the board shows no flashing light.
bogieb
Minister of Fire
Before deciding it is a board connection, check your probe connection. If it is off/loose, the stove will do a maintenance burn because it is unsure what you want it to do. Oh, and check to check that the probe is in a spot where it doesn't think it is warm enough already. Just a couple of really simple things to check before you start tearing things apart again .
Yup same as mine. I spent the morning retracing the wiring to determine if I had screwed that up, nope that is correct. It's as if it's in perpetual test mode, lights are all as they should be no blinking. I wonder if it is the esp? I'd hate like hell to think I received a bad board but what else could it be? I also noticed on the dip switch setting paper that it states on the front of the board there's an "auto / manual switch" I'll be damn if I can find that switch on my board.
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bogieb
Minister of Fire
I think that blurb means that it works with stoves that have the auto/manual switch on the controls. Could be wrong. And I believe, that your stove doesn't have that switch (it is for auto lighting), but it shouldn't affect anything but the dip switch settings.
Check your connections to the room temp sensor to the board. Don't just look at them, give them a little tug. I once had that type of issue with my former Hastings and swore to God that the leads were connected. Then I gave them a little pull and one side just slid right off. Once I gave it a good connection, everything was cherry.
Check your connections to the room temp sensor to the board. Don't just look at them, give them a little tug. I once had that type of issue with my former Hastings and swore to God that the leads were connected. Then I gave them a little pull and one side just slid right off. Once I gave it a good connection, everything was cherry.
Your correct, however after talking with the tech from where I purchased the board I finally was able to locate that portion of the board and to my surprise a switch was never installed. He was equally intrigued and requested a picture so I'm sending him this picture. My son is pointing to the portion of the board where the switch is to be mounted showing the tan area missing the switch and ZERO evidence that a switch was attached. I'm wondering with that in mind if possibly the board is defective. It's not a great picture but it's the best I could do at such a close distance without getting blurry.
![[Hearth.com] Harman P38 Major Malfunction!!](https://www.hearth.com/talk/attachments/circuit-board-missing-switch-2-006-webp.172110/ "[Hearth.com] Harman P38 Major Malfunction!!")
![[Hearth.com] Harman P38 Major Malfunction!!](https://www.hearth.com/talk/attachments/circuit-board-missing-switch-2-004-webp.172111/ "[Hearth.com] Harman P38 Major Malfunction!!")
bogieb
Minister of Fire
Maybe MCPO or gfreek will return and be able to tell you if theirs has a switch there. I looked on a couple of parts sites, and the pictures on them seem to indicate there is nothing there. However, most of the pictures are too small and/or focused on other areas, so I can't see for sure. That being said, I would think/hope that the tech would know what should be there.
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