Harman P61 manual - What does a bad Micro switch look like? 2 blink Status Error!

Hello
Final Analysis and root cause of stove failure! - Switch contacts Skip a Beat and that causes stove to fail and not shut down!
Analysis - The true story of "This Old Harman P61 Pellet Stove" A legend in it's own mind!
Testing switch continuity appears ok but it did skip a beat see video, This Harman P61 Manual Pellet stove runs on minimum fire and will not shut down after turning the mode control to off. After the fire dies down to a minimum fire the status light shows the 2 blink error and the stove keeps running. Replacing this micro switch resolves the issue. The switch can also be jumped out and the stove will shut down.
Since the micro switch must close the circuit upon ever revolution of the auger and this does not happen the stove goes into minimum fire and the 2 blink status error occurs.
The auger motor is 4 Revolutions per minute so during the operation of the stove this switch must close 4 times per minute, That is alot of closures for this old switch and you could tell that when this switch was installed the pellets kept on feeding after the mode control was in the off position!

Video of bad micro switch testing on Klien Multi-Meter


Pics of new good switch installed in stove
Pic 1-2 = New micro switch installed and stove shuts down properly!
Pic 3 - Stove with new paint!

Pics 4 - 7 = Culprit - That nasty old bad switch as you can see the contacts are corroded and pitted.

 

Hello
I would like to ad that the micro switch here is just like the micro switch used in vacuum switches and hopper lid switches and some fire door switches so the same type of failure can occur but when it comes to vacuum switches usually the bladder fails before the micro switch from my experience.
Any other comments?

 

probably ought to also note here that these microswitches haven't been produced in MANY years....and are only on very old units. Youll see them on old P61-a's, Invincibles, Invincible inserts, and some really old Advances. Most of the modern Harman's will not have them, and, as such, there is also NO 2 blink error code.....now, there is a new circuitboard coming out, the revision F board, which will have a 2 blink error (and its not the microswitch error either)....I don't think anyone has any of these yet though....totally new.

 

Thanks LW that is true
There still is a valuable lesson here with the root cause of failure that can certainly apply to almost the identical micro switch used in Harman stove vacuum switches for all models except the old Invinsibles and Pellet Pro II and is currently used in most other brand stove's vacuum switch, hopper lid switch and fire door switch.
This micro switch can fail in the exact same manner but, When used in a vacuum switch the bladder can fail with a leak from a tear before the micro switch fails.
See pics below.

 

yea, but vac switch failures are VERY rare...folks think they are the issue, they usually arent

 

Very true for Harman stoves that use relatively cool and clean inlet air to drive them but not true for most other brands that use the more hot and dirty exhaust air to drive them.
Although since Harmans last so long, I have seen them fail in very old machines.

 

they can fail, we've seen them go, but with quite literally thousands or units out there, in the last 13 months, we have sold 6....and that includes service units.

If the stove isn't feeding, its likely not this switch, but something that's causing the switch not to close, and interrupting the power to the feed motor and igniter....could be dirty, a stuck intake damper, clogged pipe, clogged intake, open door, bad gasket, etc......