Harman P38+ not starting after cleaning

[MtDew]

My stove was due for it's routine cleaning last night. Shut the stove down, waited for it to cool and gathered my cleaning tools. I removed the ESP carefully cleaned it and then performed my normal top to bottom cleaning. I vacuumed out the entire stove including the fines box. I reinstalled the ESP, filled the hopper with pellets and began to start the stove. My igniter switch is set for "Auto" and I normally run my P38+ in Stove Temp.

I turned my surge protector "on" and all the fans and the auger motor run for about 3 seconds. Then nothing! The stove just sits there. The power LED is lit but I am not seeing any blinking status LED. I tried starting the stove in Room Temp and get the same results. I double checked the fines box door to ensure it was fully seated and tight(all was good). I had a brand new ESP so I swapped that out(ESP was the same color as the original), no change. I looked over all the electrical connections, checked the hopper lid and door gaskets(all were good). As a last resort I removed the 2 connectors from the vacuum switch and jumpered the wires together. Now the stove starts, ignites and runs. It is correct to assume the vacuum switch itself is faulty or is it masking another problem? I needed heat in the house last night so I left the jumpered wire in place and it ran all night. I shut it off before leaving for work because no one will be home all day to watch the stove if there was to be an issue.
I ordered a new vacuum switch since it was relatively cheap so we will see if the new switch will solve the issue.

Any advice? Is there something else I should look at? This stove is approximately 5-6 years old, never had a major issue like this and I do routine cleanings all season long.

 

[Murph]

Air flow either in or out, tube for pressure switch, burnpot door. Could be the switch very rare though.

 

[MtDew]

Air flow either in or out, tube for pressure switch, burnpot door. Could be the switch very rare though.

Thanks for the reply. The rope gaskets on both the burn area and the ash door are in decent shape and I checked both using the dollar bill technique.
I checked the air flapper in the air inlet, checked to ensure my OAK was not blocked or restricted, all OK.
Where does the tube on the pressure switch go? Maybe something is blocking or is lodged in the opening? With the jumpered vacuum pressure switch, the stove runs normally and the flame is normal.

 

[Bkins]

I don't know where the tube goes on your stove but on mine, not a Harman, it goes to a barb at the top of the feed chute. I know Harman have a bottom feeder so I would suggest following the tube from the vac switch and taking it off and blow it out. It can be a PIA to get off the barb. Then clean the insides of the barb on the end away from the vac switch. A toothpick or paperclip will work here but be very careful if you chose a toothpick that you don't jamb it into the hole or break it off in the hole. On my Quad it will rarely get slightly clogged with fines dust/particles. I agree with Murph's statement that the switches don't usually go bad. Sometimes you can lightly, and I do mean lightly, blow into and suck out of the vac switch. The switch would need to be removed prior to this operation. If you have a Ohms meter you can check if the switch is working or not while doing the blow/suck operation. You should also be able to hear the switch working.

Let us know what you find.

 

[MtDew]

I don't know where the tube goes on your stove but on mine, not a Harman, it goes to a barb at the top of the feed chute. I know Harman have a bottom feeder so I would suggest following the tube from the vac switch and taking it off and blow it out. It can be a PIA to get off the barb. Then clean the insides of the barb on the end away from the vac switch. A toothpick or paperclip will work here but be very careful if you chose a toothpick that you don't jamb it into the hole or break it off in the hole. On my Quad it will rarely get slightly clogged with fines dust/particles. I agree with Murph's statement that the switches don't usually go bad. Sometimes you can lightly, and I do mean lightly, blow into and suck out of the vac switch. The switch would need to be removed prior to this operation. If you have a Ohms meter you can check if the switch is working or not while doing the blow/suck operation. You should also be able to hear the switch working.

Let us know what you find.

Thanks for the suggestions. The switch with shipping was around $25 so it's on the way just incase. I will remove the switch from the stove after work today and see if is blocked. I do have a multimeter so I will also check to see if is working when a vacuum is applied.

 

[Bioburner]

Seems this week we have had two gasket failures of the hopper lid and hopper extension. I would check that out again as well.

 

[Don2222]

Hello

The high temp silicone vacuum hose on a Harman goes from the air switch to the air intake tube, a nice clean place! Most other stoves go to the exhaust plenum or firebox and can easily get dirty and plugged with ash. Just try jumping out the switch to see if the stove runs. Also make sure the ash under the burnpot is clean. Is it a digital panel with LEDs or the older knob control? Also if the exhaust blower is not spinning that will cause the problem.

 

[Bioburner]

Hello

The high temp silicone vacuum hose on a Harman goes from the air switch to the air intake tube, a nice clean place! Most other stoves go to the exhaust plenum or firebox and can easily get dirty and plugged with ash. Just try jumping out the switch to see if the stove runs. Also make sure the ash under the burnpot is clean. Is it a digital panel with LEDs or the older knob control? Also if the exhaust blower is not spinning that will cause the problem.

He already got the stove to run by jumpering so that rules out bad fan.

 

[MtDew]

He already got the stove to run by jumpering so that rules out bad fan.

Yes all fans run. My P38+ has the 3 know control board. When I rotate the knob to "Test" mode, all fans and auger motor work normally. Vacuum / pressure switch jumpered out, stove starts and runs normally. Is it OK to leave it run jumpered until the replacement switch arrives? Will it cause damage to the stove?

 

[Bioburner]

Only while under close supervision. Vacuum switch is a major safety feature.

 

[Delta-T]

just for hoots...did you inspect the vent pipe? I didn't see that you mentioned it, but if the exhaust has enough ash in it, it trips the pressure switch. If you have a spark arrester screen on the end of the pipe this happen more frequently (ash catcher) and double so when the temps dip really low.

 

[MtDew]

Only while under close supervision. Vacuum switch is a major safety feature.

That's what I thought so I shut down the stove before heading in to work today.

 

[MtDew]

just for hoots...did you inspect the vent pipe? I didn't see that you mentioned it, but if the exhaust has enough ash in it, it trips the pressure switch. If you have a spark arrester screen on the end of the pipe this happen more frequently (ash catcher) and double so when the temps dip really low.

I am going to do another thorough vent pipe inspection when I get home after work. It was already dark last night after the cleaning and then the troubleshooting. I should have a few hours of daylight afterwork today. No spark arrestor screen just a round vent cap when it terminates above my roof.

 

[Bioburner]

Sounds like the stove has a ways to push the exhaust.

 

[MtDew]

Think I found the issue. I followed the small air hose from the vacuum / pressure switch to where it connected to the back of the stove. It attaches to the fines box via a 90 degree fitting that is barbed on the hose size and threaded on the other. I was able to get about a 1/4 turn on that fitting to seal it up tight. Think that was the cause of the vacuum / pressure switch not activating.
Closed everything back up and the stove is operation normally.

 

[MtDew]

Sounds like the stove has a ways to push the exhaust.

I have a Rancher and the stove is in the basement. Pipe goes up the basement wall on the inside, then thru the block wall and up the outside of the house. It runs thru the over hang / eve of the roof and then terminates 2 feet above the shingles with a round cap. Maybe 16 -18 feet of total vertical run(some in basement, some outside of house.)

 

[Bioburner]

Good to hear. Maybe cancel that switch. Invest in more pellets. Next weeks weather is supposed to be cold, at least here

 

[MtDew]

Good to hear. Maybe cancel that switch. Invest in more pellets. Next weeks weather is supposed to be cold, at least here

The weatherman said there could be a possible NorEaster storm headed our way about Wed next week. That switch was only $25 so I'll just add it to my spare parts bin. My son has the exact same stove as mine and I am the repair tech for both of them,

 

[Bioburner]

The same reason I got 2 PC45s. But the second one in the garage was under $500. No real issues other it needed a new pot switch. Great backup for the main stove in the house. After this weekend weather is for the next 7 days is supposed to be way below normal again, 15 for a high. Mid 20s average.