Harman Pressure Troubleshooting

[ifjake]

I have a Harman Advanced in my "4-season room" enclosed porch that isn't feeding pellets. This was installed by a previous homeowner, but I've enjoyed it for a few years now. I get 5-blink status that just indicates the unit has failed to light in the 36-minutes start window.

I bypassed the low pressure switch and shorted the lines together, and the feed motor does work. So, putting the pressure switch back in line, I notice that if I blocked the backdraft chute with my closed fingers, it "fixes" the pressure and the pressure switch closes, and the feed motor would start turning. But I don't really understand how the backdraft chute factors into the pressure. The damper plate swings into the unit, so it's supposed to allow air in.

Anyways, the manual says to check for closed doors or missing gasket, so I think my next move is to replace the rope gasket on the door, since I've never done that and it probably needs to happen. But I'm still a little perplexed by what was happening when I block the air intake. This is a leaky porch, so it doesn't have air intake from outside air.

Any advice?

 

[johneh]

With the air intake closed off, the combustion motor makes more vacuum.
Have you checked the chimney for a wasp's nest or a bird's nest, maybe
even a dead bird in the pipe, or could it just be needing a good cleaning
Before going to the expense of a door seal, use a smoke stick to see if it
Leaks(Pulls smoke in) with the stove on start-up

 

[Ocelot]

It sounds like the vacuum switch is working, although it may be going bad and not as sensitive as it should be. Assuming the switch is good, with vacuum issues, you have to go through each area of possible air leaks. Start with the door and ash bin gaskets by doing the dollar bill test, then check the hopper lid gasket. If all those are good, check and make sure the tubing from the vacuum switch is not blocked and has no cracks.