Harman P43 Not Feeding, Combustion Blower Only

Hey guys,

Looked around here and went through the stove thoroughly and I'm now stumped. Looking for some assistance. Here's the run down, my apologies for the TLDR version but figured more info is better than less.

I have a P43, installed in front of a fireplace and vented up with a liner. It is only a few years old, never really had any problems. I did my usual 1 ton clean a few weeks ago which involved the following:

• Vac the whole interior of the stove
• Swept the chimney and the section of straight pipe back to the vent pipe
• Removed and cleaned the ESP probe
• Removed the fine catch and vac'ed out all the fines
• Removed and cleaned the combustion blower blades

Was running great for a couple weeks and last night the stove ran out (-15 here last night, figures it would have a problem in the coldest weather). Put a new bag in this morning and started it back up. Noticed that the auger motor and distribution blower didn't go on, just the combustion blower. Thought maybe one of the doors wasn't shut all the way so I checked for blocked doors on the lid, the main door and the ash pan door. All doors sealed properly. Dollar bill trick on the main door was a little light, but can't imagine the seal would go over night. Was running fine yesterday.

Between now and when I did the cleaning I did move the room temp probe to be more in the middle of the room near my thermostat for my heat pumps. I checked the connections to these to make sure nothing had come loose or chewed by a mouse or anything. Also won't run in Stove Temp mode so don't think it has anything to do with the room temp sensor.

So I started to dig in a little further. From everything I read here it sounds like I probably have a draft issue since if I put the stove in Test mode it will feed pellets and turn the distribution blower on. I tried running the stove with my hand over the OAK intake in the back, clamped it down nearly all the way and still couldn't get pellets to feed. Verified the fine catch on the side of the stove was on tight and sealed. Checked the ESP with a meter, read around 1075 ohms. Took off the rubber tube going to the differential switch and verified that it is clear. Verified power is getting to the differential switch.

Right now I'm thinking it is something to do with the differential switch being bad. Looks like they are around $30, might just get one anyway but if someone else has any other suggestions I'm certainly all ears.

Thanks in advance for any and all help, you guys are the best.

Thanks for your quick reply. When you say jump around the switch do you mean just joining those two contacts together?

Thank you very much for all the replies. Sorry for the delay in getting back, I saw Avtek's response and shortly thereafter tried toggling the manual/auto switch and sure enough it worked. I swear on my life I must have flipped that switch 50 times, apparently 51 was the trick. Must have been stuck in between and not engaging fully to the auto side.

Thanks again guys.