York Affinity 97% Indoor Blower Motor Runs Continuously during "Call" for Heat...
Furnace Type: York Affinity 97% Efficiency
Installed: March 2009
Location: San Diego, California
This unit is to set to come on early mornings around 5:00 a.m.
Sometimes the indoor blower motor runs continuously (20-40 minutes) during the "call" for heat,
with no burners lit.
Due to the problem, a lot of parts were replaced, except for the following:
So the above still are originals.
When the problem occurs, I turn the heat to "off" and let it sit for a minute or two.
This apparently resets the unit.
Then I turn the unit back on to "heat" and that usually takes care of the problem because the unit then begins blowing hot air.
We originally thought there might have been some kind of RF interference caused by the installation a few years ago of a SMART utility meter installed by San Diego Gas & Electric, but if that was the case, the problem most likely would keep occurring throughout the day and not just in the early mornings when the unit first comes on.
This has been a real on-going mystery.
I believe the problem first started happening in 2010, about a year after the installation.
San Diego, California
If I understand your information correctly the unit only does this when it comes out of setback in the mornings?
You mentioned parts had been replaced, by who? Has the original installer been called to look at the furnace?
The furnace has self-diagnostic features that will indicate if and what kind of problems it's having.
Make sure the air filter(s) are clean. Make sure you have all supply registers open and all return registers free (nothing covering them or blocking air movement). One of the reasons some furnaces will do this is due to overheating. This can be caused by the above listed things I said to check. It can also be caused by a malfunctioning zoning system or poorly designed or installed one.
Most high efficient furnaces do what you're explaining as a way to get the homeowner's attention that it needs service/attention. They have the blower come on and run continuously, most will do this for X amount of time then reset themselves and resume heating, but only until the situation happens again. By you turning the thermostat down and then back up you basically are resetting this feature, not resolving the issue that caused it to happen.
Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.