Thelin Stove - Low DC voltage to exhaust fan

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Feb 21, 2017
Carlisle, PA
I'm on the 11th year with a Thelin Providence insert stove. Over the years I've become quite familiar with rebuilding the exhaust fan as the bearings or brushes fail. This year the stove started fine, but after a few weeks the fan RPM started to drop. I figured the motor had failed early so I swapped it with a newer one I had handy. The newer one bench tested strong and strangely, the fan I just removed also bench tested strong. After installing the newer fan, RPMs were a bit higher, but still low, and over night the fan slowed to a crawl.

The stove is clean, there are no obstructions or fan interference. The electrical connections are clean and tight. I appear to be getting low DC voltage from the fan control circuit. I'm about to pull the unit to do more testing. If the fan control is bad, I think it's part of the main board which is an expensive fix.

I'm considering the install of a separate manual fan control. This will be a simple variable 12v DC power supply with a knob installed in the existing panel. This will give me independent control of fan RPM so I can fine tune to air-flow for max efficiency. All of the other stove safety sensors would be unaffected (exhaust flow, over temp, etc) so I don't see a safety issue and I can install a separate fan power supply for a fraction of the cost of a new controller board.