Bearing in small motor for little fan on heating unit

I found some good answers on this website: https://www.waterheaterhub.com/water-heater-leaking-from-the-top

I hope it helps.

Is your central heating unit a heatpump w/ electric heat or natural /propane gas ? And what is the water heater, gas or electric ?

That may be a 24V Tstat and there would be a little transformer in the boiler that powers the Tstat. Sometimes those burn out.

Check line voltage if good then controlle volts that is 24 Ac smell the transformer clean draft hood, burners, fan assembly and filter. Call for heat if nothing check for 24 volts at gas valve if good change thermlocuple. Need more help ask give more info about furnace and what its doing or not doing

If the zone valve was replaced and wired correctly then it is likely the zone controller if u have one. Manually open the valve and turn the tstat up if it begins to circulate then it is a controller issue. If you still get no heat (circulation) than it is the circulator pump or the pumps controller. Its best to test those individual parts with a multimeter to avoid buying parts not needed

I’m happy to help further over the phone at https://www.6ya.com/expert/steve_e294c1922e4bed38

check to make sure fan blade is tight on motor shaft.KILL POWER TO UNIT FIRST

We had the same problem - the hot water would only be hot for 3 -5 minutes and shut off, then we had to turn the water off, wait a few minutes, and do it again. VERY FRUSTRATING.

Solution: The Rinnai serviceman showed me the heat-exchanger blower/fan: It was clogged with dust and moths.

Another clue: Our Rinnai was extremely noisy when the heat came on. After the fan was cleaned and replaced, it is nearly silent.

If you are reasonably mechanically inclined:
TURN THE BREAKER / POWER OFF to the unit.

The blower-fan is located in the lower central area of the unit (at least on our unit). If you draw imaginary north-south, east-west lines through the center of the unit, the fan is in the lower-left quadrant. There is a spring clamp securing the black rubber accordian-like tube to the fan. There are two screws that secure the fan to the unit. there are two plugs that connect to the fan, as well as a third air-flow sensor that should be removed. then you can look at the fan unit, as well as the grill on the underside of the heat-exchanger that should be cleaned.

My thought was to go out and get a simple bug-screen, and place it over the air-input outlet vent going outside, but the repair guy said that although it may sound good, if that screen ever gets clogged, or reduces airflow to the Rinnai, then the unit will work harder, or even shut off, giving the same problem.

Is there a booster motor for the burner? I have seen these stick and make a furnace not turn on. The thermostat trips and you hear the furnace click on but nothing else happens. The booster is a small electric motor connected to a small duct. Take the booster motor loose and turn the fan by hand. Usually they will start working after you do this. Make sure furnace is shut off when you do this. Some booster motors have ports to oil them also.

Sounds to me you are low on freon and the evap coil in icing up