Greetings Mike welcome to the Forum.
I'll tell ya right up front, I'm not familiar with either of the units you're using there, but I got a fair concept of control wiring, so.....
It may be one thing, and that's a Temp Switch, which is downstream from your Furnace. It shuts the unit down if the air goes overtemprature (like over 180°), and the second part of the Stat holds the Blowers off, till the air comes up to a reasonable temp to be useful.
Usually it's a box on the outside of the Duct, which has two sliders in it, and you might find the "air rise" slider, and drop the temp down on it a few degrees.
My best shot !
Have a good Day !
S.W.