If you have a 5er, chances are you have a vent fan that you cannot reach.
The thermostat will turn the fan on and off, but you cannot control the fan speed. I decided that I needed a way to control that fan. I found that a 3/4 inch PVC pipe coupler was almost the right diameter to fit over the fan speed control knob. It was just a bit small. Also, the knob has a position indicator that sticks out from the knob.
I took the 3/4 inch PVC coupler and cut a 1/8 inch groove in the coupler with a close quarter hack saw. Then, I took a Dremel tool with a sanding disk and enlarged the opening in the coupler until the knob would fit into the coupler.
To make it easier to see when it is 3 feet above your head, I painted a black stripe on the coupler so I would know where the groove was cut. Then I glued it to a 3 foot long piece of 3/4" PVC pipe.
Works great and it's cheap!