Disconnecting a thermostat is not a complete test
Different systems use different control arrangements. A furnace can also run a blower as part of a protective response. For example, Daikin's DR96TN instructions describe continuous blower operation in several specific fault conditions. Those examples show why a thermostat-free fan event is not a universal board test. They do not identify the condition in your furnace. Daikin control troubleshooting.
Do not reconnect wires by trial and error, bridge terminals, run with the door removed, or alter safety switches. If the wiring is currently changed, keep the equipment out of use until qualified service gives appropriate instructions and restores the approved setup.
Give the technician the actual sequence
Explain what the fan did before the disconnect, what changed afterward, which wires or plug were removed, and whether power was interrupted. Share existing photos. If you do not know the terminals, say so rather than guessing.
Note whether ramping happened with a heat request, immediately after power returned, or with no ordinary request. Do not repeat the experiment to gather a better sequence. A professional can decide how to safely isolate the controls using the correct documentation.
Ask what evidence supports a board or motor replacement
The useful review identifies the control request, board response, motor behavior, wiring condition, and any stored or active fault. Ask which of those has been confirmed and which remains uncertain.
If a board is recommended, ask what test shows it is at fault rather than responding to an input or protective condition. If a motor or module is recommended, ask how its failure was distinguished from its power supply or control signal. Those checks are professional work; there is no homeowner electrical test to add here.
Ask whether the proposed part is approved for the exact unit and whether the repair includes restoring configuration and verifying operation. A new board installed with an unresolved input problem would leave the central question unanswered.
Keep the larger decision proportional
Replacement may deserve comparison if the confirmed condition, parts availability, and overall equipment condition support it. Repeated ramping alone does not establish that replacing the whole furnace is necessary.
Your next step is to disclose the wiring changes when requesting service. Ask for one explanation that connects the fan behavior to a confirmed condition, restores the intended controls, and identifies what was checked before the furnace returns to use.