Hydro-Flame furnace 8525-IV (2000 GeorgieBoy)
Normal ops- Fan starts, then after several seconds the furnace lights and would run until set temperature reached, flame off and fans runs until units cools.
Problem: 1. Start and light-off normal but burner would cycle. Flame off, fan runs then flame on again, and cycles flame on and off every few minutes until thermostat temp reached. (hard to notice) Unit was turning flame off due to overtemp inside unit.
2. Noticed it took much longer to heat living area and air through floor vents seemed weaker. Fan also seemed noisier, more vibration..
Although the motor and blower wheels can possibly be replaced without removing the furnace, it was really tight quarters and I removed the whole furnace. Initially I could see the plastic blower wheel was warped, and after checking the motor it had rough spots in rotation. The Combustion wheel was fine. (metal). Also checked the Burner assembly while it was on the bench. Did replace the motor and blower wheel.
GeorgieBoy part: This caused the problem:: The MH uses floor ducting for heat in the living room. The furnace and the extension box were removed together. The hole into the ducting was seriously blocked. The ducting mounts under the 5/8" OSB flooring, which has a moisture barrier fabric under the OSB. The fabric is then the top of the duct. This fabric had sagged down until it was blocking most of the opening into the ducting.
The air from the furnace was going between the fabric and the floor and not thru the ducts.. I had looked in the ducting with a mirror for blockage, but the problem was off the side of the main duct. The blocked airflow was causing the overtemp.
The opening for the furnace was also partially blocked by the carpet and padding extending into the opening about an inch across it's full width..
I trimmed the material clear of the opening, re-framed the opening. Glued the fabric up to the OSB and used a 4 inch wide aluminum strip to hold the fabric in place.
The furnace works better than before, the real problem was hidden and only apparent after the whole thing was removed.