P38 harmon disturbution fan randomly comes on

[C4boom]

I went to start my stove for the season the stove would not light and I was getting a 3 blink. ESP probe issue, so I replaced the ESP. Probe. The stove runs, but I'm getting up. Relatively high idle and the distribution fan comes on randomly. Even when the room is up to temp room is 70° and room temp setting is set to 50⁰. It comes on for a couple seconds, then turns off.

ran fine. All last season.

Attached a photo of the flame at idle.

 

[ARC]

so I replaced the ESP. Probe

First question would be did you replace ESP probe with the same color probe? Harmon uses a Red and a Black probe they are not interchangeable. Some control boards have dip switches that can be set for either probe.

 

[C4boom]

First question would be did you replace ESP probe with the same color probe? Harmon uses a Red and a Black probe they are not interchangeable. Some control boards have dip switches that can be set for either probe.

Yes replaced black with black.

 

[ARC]

Yes replaced black with black.

Was it a after market probe?

Did you accidently unplug room sensor when changing ESP?

 

[C4boom]

Was it a after market probe?

Did you accidently unplug room sensor when changing ESP?

View attachment 330745

The wall thermostat is working as when the room gets up to temp the stove ramps down ( but not as low as it use to) also I think if it is unplugged it throws a 2 blink status light. The probe was from my harmon stove distributor don't know if it was truly harmon brand or nnot.i will go there tomorrow and ask them the brand.

 

[zrock]

If im reading this right the fan is coming on during operation but when its in a non head mode or coming on when it should not be? Probably not the case with you but something to look at. A few years ago i had put a cyber power battery backup on the stove, i never put 2 and 2 together for a long time but when the stove was of the fan would kick on randomly for a few seconds. One day i decided i would unplug the backup discharge it and recharge to cycle the battery, hooked up a very expensive room fan and it went up in smoke in about 10 seconds. I then realized that the backup was power surging and turning the fan on. Since i have removed it this has never happened again, was surprised it did not blow the board out of the stove. Of course cyber power would not come good for anything not that i would have put another one on any pc of electronics i owned.

 

[ABusWrench]

Nobody has asked, so... Was the stove plugged in over the summer and is it plugged into a surge protector?

 

[C4boom]

Nobody has asked, so... Was the stove plugged in over the summer and is it plugged into a surge protector?

Stove was not plugged in. Over the summer

 

[C4boom]

If im reading this right the fan is coming on during operation but when its in a non head mode or coming on when it should not be? Probably not the case with you but something to look at. A few years ago i had put a cyber power battery backup on the stove, i never put 2 and 2 together for a long time but when the stove was of the fan would kick on randomly for a few seconds. One day i decided i would unplug the backup discharge it and recharge to cycle the battery, hooked up a very expensive room fan and it went up in smoke in about 10 seconds. I then realized that the backup was power surging and turning the fan on. Since i have removed it this has never happened again, was surprised it did not blow the board out of the stove. Of course cyber power would not come good for anything not that i would have put another one on any pc of electronics

I'll test the outlet for surge .

 

[ARC]

I would say a bad New ESP probe, creating high idle which is causing stove to sporadically heat up enough to turn room blower on.

 

[Washed-Up]

The only other thing I can think of is a bad board…keep in mind this is the worst case scenario and you should always work the small stuff into the bad

 

[C4boom]

The only other thing I can think of is a bad board…keep in mind this is the worst case scenario and you should always work the small stuff into the bad

Sadly you where corect. Found A OEM Harmon board for A P43 for a $193. Put that in today, stove runs great. I have to leave the switch into manual mode Though, because I don't have the igniter and P43 box, but those are on the way.