Harmen XXV diagnosis Question

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Petras

New Member
Oct 24, 2025
6
Canada
Hi, when my combustion blower is running. There is a loud rumble noise. Pretty consistent when it’s running.

When I pulled the blower out of the stove. Plugged it in. There’s no noise and the blower sounds great.

Stoves clean and otherwise operates great.

The noise is unbearable and I won’t be able to run the stove till fixed.

Any idea what is going on here?
 
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Check that the fan blade is not rubbing on the housing. You can adjust with the set screw on the shaft. Had to adjust mine after cleaning.
 
Check that the fan blade is not rubbing on the housing. You can adjust with the set screw on the shaft. Had to adjust mine after cleaning.
The noise occurred before cleaning. That’s what led me to taking it all apart.

Makes me wonder if there is a gasket that’s finally worn out? But I believe the xxv just has metal on metal with the wing nuts. I added a picture for extra context.

This is the part itself. I run it outside the chamber and it sounds great. Once I put it back in, it’s terrible..
 
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[Hearth.com] Harmen XXV diagnosis Question
 
Alrighty. So when I hold the combustion blower, it makes no noise in my hand. The fans spin. Sounds great.

If I rest it down on the a lip of the stove and plug in - The section behind the front propeller blades rattles. More or less replicating the sound.

Safe to say a new combustion blower will fix this?

Go OEM or aftermarket?
 
The noise occurred before cleaning. That’s what led me to taking it all apart.

Makes me wonder if there is a gasket that’s finally worn out? But I believe the xxv just has metal on metal with the wing nuts. I added a picture for extra context.

This is the part itself. I run it outside the chamber and it sounds great. Once I put it back in, it’s terrible..
Could the frame be twisting when mounted? Maybe the sound is coming from something else that is vibrating nearby?
 
Could the frame be twisting when mounted? Maybe the sound is coming from something else that is vibrating nearby

Could the frame be twisting when mounted? Maybe the sound is coming from something else that is vibrating nearby?

Could the frame be twisting when mounted? Maybe the sound is coming from something else that is vibrating nearby?
I doubt it’s twisting. But I’ll look into it a bit.

once I replace the blower, I’ll know if it’s something else. Worse case, I have an extra combustion blower. Best case. The noise goes away.

To those that have replaced the combustion blower. Is it as simple as pulling the connectors apart and reconnecting the new unit.
 
How old is your stove? Mine didn't seem too noisy until it got about 10 yrs old. Of course it depends on hours not years.
Changing the combustion fan fixed mine.
 
I doubt it’s twisting. But I’ll look into it a bit.

once I replace the blower, I’ll know if it’s something else. Worse case, I have an extra combustion blower. Best case. The noise goes away.

To those that have replaced the combustion blower. Is it as simple as pulling the connectors apart and reconnecting the new unit.
I know on my P43 I would need to pull the fan off the shaft to slide the motor shaft out. The last time I tried to get the fan blade off a normal hex key did not work. I have bought a 1/4 ratchet set of small hex's to try next time. I have another fan blade want to install (my spare)
 
How old is your stove? Mine didn't seem too noisy until it got about 10 yrs old. Of course it depends on hours not years.
Changing the combustion fan fixed mine.
Was it an annoying rumble noise you had? That’s essentially what I’m hearing.

I’ll replace the combustion fan and see what happens. Seems to be the common suggestion.

I’ve run this stove. On continuous. For 6 months of the year. For the last 5 years straight. Gets some very heavy use. About 20,000 hours of run time. lol
 
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Was it an annoying rumble noise you had? That’s essentially what I’m hearing.

I’ll replace the combustion fan and see what happens. Seems to be the common suggestion.

I’ve run this stove. On continuous. For 6 months of the year. For the last 5 years straight. Gets some very heavy use. About 20,000 hours of run time. lol
Yeah it is probably the fan. Don't remember if it was a rumble but it was annoying. I first tried oiling the motor but that didn't help.
I only burn 2 ton a year so mine took longer to fail.