if you shin a light on the back of the coils in the air handler is the light suppose to go thru?
i would think it depends on the fin spacing, depth of the coil, and cleanliness. some coils yes, you would see the light, others, no you won't see the light.
I would be worried if it doesn't. Means my coil is dirty.
Hey, is that a way to check your coil's cleanliness?