P38+ circuit board faulty?

[slarkin]

My P38 stopped unexpectedly last night. With my propane furnace costing 2X the going rate for pellets, I need to fix it ASAP. Last year I replaced the combustion motor and distribution motor. This problem is different.

When starting up, the stove does not begin its normal startup routine (combustion motor on, distribution motor on, augur runs one cycle) until the dial reaches the "turbo range". These startups always began before at the 1-2 setting, but no longer do. Sounds to me like the rotary switch is faulty. Does anyone agree? I am not a technogeek, so I don't want to trouble-shoot the board with my multi-meter.

My dealer does not provide service - he just provides parts. If I can be reasonably sure of which part is faulty, I can probably get him to provide a new one to me. I think this rotary switch is provided as part of the circuit board.

The pellets are feeding okay, but the stove immediately shuts down when I back the dial off from the turbo setting. I have been using this stove for 3 years and am well-versed in its operation. If you have knowlege of the circuitry and electronics, perhaps you can help me.


Thanks

 

[rayttt]

mine never started all fans unless I went to turbo..if I turn it up a little the convection blower may or may not start.if I goto turbo ..the convection motor starts.
the combustion blower starts in all cases.

if your stove shut off during the night..I would assume it stopped feeding pellets..could be a large length pellet bridging the augur input, presumable it would still be bridged.

 

[Jester]

The P38 shouldnt activate its self check cycle unless you turn it to turbo then back down.

 

[slarkin]

It is not a pellet feed problem. I have used this stove for 3 years and am well-versed in its operation. Had a LOPI before and much prefer the Harman. Electrical issues are recurrent with these, however. I run it 24/7 from October - April and it gets tired pretty fast. Ran 7 tons through it last year.

The problem is not mechanical. The startup does what it should, but as soon as I back off from turbo, it shuts down. If you have knowlege of the electronic issues with this stove, I could use your help.

Thanks

 

[rayttt]

you back off of turbo and both the combustion and convection fans turn off??
id say the control board mostly..the potentiometer for the feed rate could be bad..but Id assume its mounted onto the board..I havent taken mine apart so I dont know if the potentiometer is mounted on board and not connected via wires.
if the combustion blower IS blowing then it needs proof of fire..so Id look and clean the ESP probe

 

[djarseneault]

my first thought is it is the ESP.
When the potentiometer goes bad on the Harman control boards the symptom is usually "dead spots" in the dial's range. What I mean is it will work on 1,2,3,5 ect but not 4 or something like that. The other reasons I suspect the ESP are:
1 the P38 has a higher fail rate for ESPs than the other Harmans, not sure why.
2 The ESP is a lot cheaper than a control board.
3 If you replace the ESP and that doesn't solve it, you have a spare ESP, and that is a good thing (see #1).

 

[slarkin]

I will try the ESP probe. I replaced the circuit board yesterday and it still does not run.

Thanks for the advice. Burning Propane and hating it.

 

[MCPO]

Maybe not the answer but be sure the feed rate knob didn`t get turned too far one way or the other and is now not positioned correctly. I have to be careful not to force mine as it did happen to me twice already.

 

[slarkin]

Checked the ESP probe. The test was easy in this case. As soon as I unhooked it from the circuit board, I checked again and found that the exhaust fan started working normally. Was briefly tempted to run stove without it temporarily, but wisely thought better of it. I know the ESP is a safety device and sure wouldn't want to burn down the old homestead. Tried cleaning and re-installing, but still no luck.

Went over to the dealer and got a new probe and installed it. Now the stove works great. I am much happier and warmer.

By the way, this little stove is my primary heat source for a 2800 square foot home. As long as it isn't real windy, it does the job down to about -10. Every few years we see over 40 below, so it is good to have the propane furnace as auxiliary.

Insulation is even more important than upgraded heaters. My home is an energy star and I still look for extra places to increase efficiency.

Thanks everyone for the advice.

 

[ducker]

as a new owner of a p38 love hearing this... how much was the probe?

 

[hossthehermit]

Checked the ESP probe. The test was easy in this case. As soon as I unhooked it from the circuit board, I checked again and found that the exhaust fan started working normally. Was briefly tempted to run stove without it temporarily, but wisely thought better of it. I know the ESP is a safety device and sure wouldn't want to burn down the old homestead. Tried cleaning and re-installing, but still no luck.

Went over to the dealer and got a new probe and installed it. Now the stove works great. I am much happier and warmer.

By the way, this little stove is my primary heat source for a 2800 square foot home. As long as it isn't real windy, it does the job down to about -10. Every few years we see over 40 below, so it is good to have the propane furnace as auxiliary.

Insulation is even more important than upgraded heaters. My home is an energy star and I still look for extra places to increase efficiency.

Thanks everyone for the advice.

If ya don't mind me asking, how much was that little jewel?

 

[djarseneault]

Checked the ESP probe. The test was easy in this case. As soon as I unhooked it from the circuit board, I checked again and found that the exhaust fan started working normally. Was briefly tempted to run stove without it temporarily, but wisely thought better of it. I know the ESP is a safety device and sure wouldn't want to burn down the old homestead. Tried cleaning and re-installing, but still no luck.

Went over to the dealer and got a new probe and installed it. Now the stove works great. I am much happier and warmer.

By the way, this little stove is my primary heat source for a 2800 square foot home. As long as it isn't real windy, it does the job down to about -10. Every few years we see over 40 below, so it is good to have the propane furnace as auxiliary.

Insulation is even more important than upgraded heaters. My home is an energy star and I still look for extra places to increase efficiency.

Thanks everyone for the advice.

good to hear you got it fixed. Just wanted to make one point. Your test method of unplugging the ESP from the control board is flawed because all you did was activate a "fail safe" that is built into the circuit board. The circuit board sensed no probe installed and turned the exhaust blower on high. And you would not have been able to run the stove without the ESP, it is not just a safety device, the readings from it are what the circuit board uses to set blower speeds and feed cycles.

 

[slarkin]

You really seem to know your stuff on these Harmans. I am sure grateful for your help.

Previous question about cost- The stove cost me about 1950 three or four years ago. The parts I installed have all been free because of the warranty.