Pressure switch not activating.

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Fbd

New Member
Dec 19, 2019
10
Connecticut
Hello everyone. I am happy to report the responses from my last post helped me successfully diagnose my Maxim issue. However, now I am working with a Harman pellet stove model p43. The unit just stopped running at some point. I noticed the feeder wasn't moving pellets into the burn chamber. Combustion fan is running. Started out by making sure the cover switch was good. Removed the casing, wires are fine. Then I did some research and found a trick to bypass the pressure switch to see if that is the cause. I jumped the wires for the pressure switch and the feeder runs. My first fix was to replace both door gaskets and the glass gasket. Adhesive cured for min 12 hours. Switch wont activate. Order and replaced the pressure switch, still wont activate. BUT when I suck air through the tube while its attached to the pressure switch and the wiring is connected (very lightly as to not damage the switch) I hear the valve click and the feeder begins to run. Took apart the burn pot and VERY thoroughly cleaned the inside of the stove. The I attached the switch tubing to the air valve coming from the stove and sucked in and out and there did not seem to be any blockage. I even used compressed air to maybe clean out the airway just in case. Still the switch wont activate. So the switch is good, the wiring is good, the cover switch is good, the airway does not seem to be clogged and the stove is thoroughly cleaned. Any ideas on what to try next?

TL/DR: Something is wrong with the pressure switch mechanism in my Harman p43.
 
Did you check the fines cover?
 
Is the flue clear?
 
Right side of stove (when facing front & behind the control board) on the side of the feeder assembly. It's held in place with a wing nut & yes there is a gaket on the cover that seals the fines box/feeder assembly. I don't have pictures on this PC, but a search for fines box should steer you to its location.
 
Here is what it looks like with the cover on and then removed:
 

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So I did find and clean the fines cover and that seems to get the unit working. For a while... it suddenly shut down again and tripped the breaker. There wasn’t any power. I checked the board and the fuse was blown. I replaced the AGC 250v 6A dude with an MDL 250v 6A fuse. I don’t know if this is the reason is still won’t work but as soon as I plug the unit in it trips the breaker. I can’t find any shorts right now so I don’t know if that is the problem or not. Any other suggestions? Is it ok to use those fuse types interchangeably.
 
If it wasn't tripping the breaker before cleaning the fines box, I would check to make sure you didn't pinch a wire whe putting everything back together. Also check the main board connections to make sure all are plugged in tightly, you may have disturbed something while you were behind it.

Also, you didn't disturb the slide plate when cleaning the fines box?

Has the igniter ever been replaced? I've seen where people have not pulled the connections back into the air tube (feeder assembly) far enough and they were still under the burn pot which results in melted connections (bare) that can contact the pot or feeder assembly and short out; if everything else checks out, I would look in the igniter area to make sure this isn't your problem.
 
If it wasn't tripping the breaker before cleaning the fines box, I would check to make sure you didn't pinch a wire whe putting everything back together. Also check the main board connections to make sure all are plugged in tightly, you may have disturbed something while you were behind it.

Also, you didn't disturb the slide plate when cleaning the fines box?

Has the igniter ever been replaced? I've seen where people have not pulled the connections back into the air tube (feeder assembly) far enough and they were still under the burn pot which results in melted connections (bare) that can contact the pot or feeder assembly and short out; if everything else checks out, I would look in the igniter area to make sure this isn't your problem.
This was most certainly the issue. It worked well but now the stove will not run a shut-down cycle any more. When you turn it off it just shuts right down without cycling pellets through the feeder.