Harman Accentra Insert distrbution blower won't turn off

[padlocked17]

Good Evening,

Just as the title describes. I replaced the Accentra blower a week or two ago. We've run it several times with no issues. Now all of a sudden the distribution blower will not shut down. The light on the side doesn't show the distribution blower as running, but it certainly is (cold air blowing from the top of the stove). We tried doing a hard reset, (Power off, Switch to Off, Power back on) but the blower just comes back on with no light showing that it should be on.

Any help would be appreciated.

 

[DAKSY]

ESP dirty?
Damaged

 

[padlocked17]

ESP dirty?
Damaged

I'll have to check. That dang ESP probe is the bane of my existence if that's what is causing this.

That would trigger the distribution blower to run without a light on on the panel?

 

[padlocked17]

Cleaned the ESP and the distribution blower is still running continuously. Even after a hard reset (Unplugging, switch to off, power back on).

No lights on the board indicating the distribution blower should be on.

 

[Montecarlossfan]

Cleaned the ESP and the distribution blower is still running continuously. Even after a hard reset (Unplugging, switch to off, power back on).

No lights on the board indicating the distribution blower should be on.

without the light on it sounds as if one of the triacs is shot on the board.

 

[padlocked17]

without the light on it sounds as if one of the triacs is shot on the board.

Does that require a complete board replacement or is there some other fix?

 

[Montecarlossfan]

Does that require a complete board replacement or is there some other fix?

It’s a board replacement unless you have experience repairing electronics. ... is the fan speed able to be varied or is it just full tilt as soon as the stove is plugged in?

 

[padlocked17]

It’s a board replacement unless you have experience repairing electronics. ... is the fan speed able to be varied or is it just full tilt as soon as the stove is plugged in?

Full tilt as soon as it’s plugged in. Switch position is irrelevant. If the stove has power, the fan is running full speed ahead.

 

[Montecarlossfan]

Definitely sounds like a shorted triac , combustion motor is off as well I assume. Unfortunately it sounds like a new board at this point if it is on and not commanded on.. the link below is another forum memeber who replaced the triacs to resolve an issue. There is always the slight slight chance it is a bad control pot but the led would be lit if it was being commanded on. A triac basically is a solid state relay without getting into the nitty gritty of how they work.

Triacs replaced

 

[padlocked17]

Definitely sounds like a shorted triac , combustion motor is off as well I assume. Unfortunately it sounds like a new board at this point if it is on and not commanded on.. the link below is another forum memeber who replaced the triacs to resolve an issue. There is always the slight slight chance it is a bad control pot but the led would be lit if it was being commanded on. A triac basically is a solid state relay without getting into the nitty gritty of how they work.

Triacs replaced

Combustion motor is off.

I've got no qualms with replacing a triac or at least giving it an attempt. I busted out the Multimeter and it looks like of the 4 triacs I have on the board, only one is reading differently. 3 are showing as nothing from A1 to A2 or from A2 to the Gate. They are showing ~67 ohms from A1 to the Gate. The oddball out is showing 0.4 ohms from A1 to A2 and ~67 ohms from A1 to the Gate and ~67 ohms from A2 to the Gate. I think I can logically deduce that the one labeled Q3 (the one with abnormal readings) is my culprit then?

Looks like the part is made by ST as listed here with the associated datasheet here.

In looking for the triacs, it seems Newark.com only has them available on cut tape vs individually and they are labeled as part # T835-600G-TR. I don't see any issues with the difference (spec sheets appear to be the same) so I'll probably order some of those and see about swapping them out. $0.50 + an hour seems better than $250 for a new board.

Am I missing anything here?

 

[Montecarlossfan]

Although an out of circuit test would be a definitive way.
Esentially out of circuit a diode test would be from gate to a1 and a2 , one should read a voltage drop and one shouldn’t , reverse the leads and the opposite should read a drop and the other shouldn’t.
I think you found the culprit based upon essentially a short between a1-a2 though, I don’t have a board in front of me but you could trace the wiring harness pin that connects to the blower right to the triac. You could opt for the same ones or find through hole equivalents and heatsink them if I recall there is room to do so.
I’d say it’s worth a shot , there are opto isolators ahead of the devices IIRC but I’d be surprised if one is bad.

As for the packaging from mouser/digikey that’s all it is, most of the reel stuff is for high speed assembly machine loading that’s all but it’s the same part.

I restore older amplifiers and such but if something is repairable I’ll usually spend the time to fix it especially as in your case it’s always a .50 cent part.

 

[padlocked17]

Although an out of circuit test would be a definitive way.
Esentially out of circuit a diode test would be from gate to a1 and a2 , one should read a voltage drop and one shouldn’t , reverse the leads and the opposite should read a drop and the other shouldn’t.
I think you found the culprit based upon essentially a short between a1-a2 though, I don’t have a board in front of me but you could trace the wiring harness pin that connects to the blower right to the triac. You could opt for the same ones or find through hole equivalents and heatsink them if I recall there is room to do so.
I’d say it’s worth a shot , there are opto isolators ahead of the devices IIRC but I’d be surprised if one is bad.

As for the packaging from mouser/digikey that’s all it is, most of the reel stuff is for high speed assembly machine loading that’s all but it’s the same part.

I restore older amplifiers and such but if something is repairable I’ll usually spend the time to fix it especially as in your case it’s always a .50 cent part.

Thanks for the guidance on this. Parts are in the mail, so hopefully I'll be able to knock that out and make it a $0.50 fix vs a $250 one. I'll post up results once I get the board fixed up.