Harman - Distribution Blower Fluctuating in Speed

There was a thread on that not to long ago, I'll see if I can link it here!

Edit: Link is below!
https://www.hearth.com/econtent/index.php/forums/viewthread/80494/

Here is some of the tips to try.

Lousyweather said:

the light dims as well? ALL of the lights, or just the dist blower light? Unlikely its the ESP probe, more likely the circuit board......Usually the bad ESP's are either bad or good......not in-between. What about your power supply? The distribution fan is the highest demand fan on high inthe unit, so, if your stove were starving for power, it might be evident in the distribution fan first. Unfortunately, your unit is no longer under warrantee. Have you tried running the blower itself connected directly to line voltage to see if its the blower at all? If you connect it directly and it doesnt do this, you will have eliminated the blower as the issue. Next is the circuitboard........a bad spot on the rheostat? Not unknown.

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Richgvt said:

The blower on my p68 used to cycle on and off and was being irregular. Just did not seem right. This was after a power surge. The power kept turning on and off rapidly. I finally got the dealer to install a new circuit board which fixed it.

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I would say if the voltage is fluctuating to the blowermits probably the board. If its steady, Then the blower is at fault. Blower is the cheaper of the 2, But suspect control board is to blame!

How did the dealer check the control panel?

is blower fluctuation rapid or over the course of a few minutes?

The control board does have the ability to over-ride the blower speed you have set. Depending on the temp the ESP is reading and the stove set point temp that is the default temp for the stove/room temp setting you have selected, the blower can automatically adjust itself to blow slower or faster. If it is rapid like you said it is, it may be the board. How long was the tech at you home for trying to diagnose the issue? They should of stayed a while with the DDM plugged in and monitored the voltage going to the blower.

Have you checked all the connections going to the circuit board, especially from the probes? This resembles symptoms of fluctuating inputs on other types of systems that I've worked on. Just a thought, worth a try, and costs just a little time.
Make sure all connectors are seated fully, and the pins are fully inserted. I would also work the DIP switches back and forth a few times (but make sure not to change any settings!). The fact that it has "cured" itself is another indicator of a flakey connection. Intermittent problems are a real bear to find, as you know.

My Harman P68 has this same problem. It happens mostly at night when I turn the stove to Room Temp mode from Stove Temp mode. It typically shuts off for a few hours, then it reignites in Room Temp mode. After it ignites, the fan was doing the same thing, alternating from low to medium speed like the revving of an engine almost. If I turn the power off and on and switch it back and forth from Stove Temp mode to Room Temp mode and I can eventually get it to stay consistently on high fan speed. Like your issue, my combustion blower light was fluctuating just as the fan speed was. After a few weeks of this, the stove would turn itself on in the night on Room Temp mode and sometimes the distribution blower wouldn't even turn on at all. I called a tech out, and since it seems to only happen from a cold start in Room Temp mode I wasn't able to replicate the problem. They replaced the distribution fan and now it still fluctuates when it starts up in Room Temp mode, but it hasn't done what it did before where sometimes the distribution fan wouldn't work at all. That leads me to believe that perhaps it was partly the blower and also the circuit board? When the distribution fan was replaced, they put some sort of gasket fabric material in between the fan and a metal sheet to prevent noise, but it pushed the distribution fan out of place just enough that there was a metal on metal noise on medium speed, so I took out the gasket fabric and the noise mostly went away, although I think the fan is louder than the original one was...any suggestions or ideas?
thanks

I replaced my ESP probe and it fixed the same problem on my stove. I'm pretty sure it was how it was connected to the board, because when I pushed the plug into the board manually the distribution motor and light would remain consistent and when I let go it would fluctuate. The old ESP probe didn't clip into the socket on the board while the new one clicks in and doesn't move at all. A new probe is only about $56.

Had a similar problem with my dist fan turning off and on rapidly. Also a few 3 blinks. Needed new ESP..and this was on a new stove.

Also, just had to replace the dist blower due to it making an odd noise. Warranty replacement doesn't have the odd noise, and is MUCH quieter overall.