Wiring to run furnace fan only

[SaintFrag]

Furnace: Frigidaire FG6RC 060C-12a (903045F)
Thermostat: Honeywell RTH230b - owner's manual​

I poked around the internet and can't seem to find anything to aid in my ignorance. Perhaps it's lack of sleep from a newborn, so bear with me.

I often have a desire to circulate the air in the house due to temperature differentials between floors. For instance, last night it was 76 upstairs due to the beautiful sunshine, but 67 downstairs. The furnace has 5 low voltage terminals as does the thermostat. They're wired 1:1, meaning R to R, W to W, etc. I attempted turning the thermostat to cooling mode, dropping the desired temperature down, and turning the fan from Auto to On. No dice.

How would I adjust the wiring to allow the furnace fan to be run by itself?

Thank you!

 

[Ludlow]

Does the furnace have a control board or is it an older unit?

 

[coaly]

When the fan control is in auto, the fan should run automatically as needed. When "On" is selected it should run continuously in the heat mode only.

In your manual, page 33 gives heat and cool modes, (has delay turning on and off) page 34 gives fan only mode;

Fan Mode:

1. On a call for fan operation, the thermostat
applies 24 VAC to the G terminal on the
furnace control board.

2. The circulating air blower is energized immediately on the heating speed.

3. If the furnace is operated in the continuous
ON position at the thermostat and is then
switched to AUTO, the circulating blower
will operate for a specified delay (factory set
at 120 seconds)

Simple low voltage connections are as follows;
So to troubleshoot fan only operation, make sure you have 24 volts at the green wire from t-stat to circuit board for fan only operation.

White is 24 volts with a call for heat, and green and yellow is 24 volts when a call for cool to turn on compressor.

Red is common, so measure between red and green, (fan) or red and white, (heat) or red and yellow (cool) at the board.

This will start you at page 33 giving you what the other t-stat wires do. (4 used for heat and cool)
https://www.manualslib.com/manual/112920/Nordyne-G6rc-90Plus.html?page=33#manual