Dial in air return?

This is a 1979 Ruud HVAC in a 1940 house…what is that dial and cut wires in the return?

Also, it should be noted that this entire unit seems to be made of more duct tape than metal. Blasting cold air near the unit while the second floor is sweltering. (90 degree day here in northern Virginia)

Humidistat control.

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Thanks, Jeffrey.

Assuming since the wires are cut that it didn’t work out so well…Like most houses around here, ducts are small, have long runs, and lots of turns…and the attics are poorly insulated. Someone was probably looking for a panacea and didn’t find it, and had the humidistat taken out. Decent working theory? Does the dial look like it dates to the '79 HVAC?