Rear Fan Heating Controls

[1999montana]

I just noticed that the rear heater fan does not work from the rear control console. The switch on the dash control is set to rear, but the fan will not operate on any setting. The front switch overrides the rear, so I switched to the front dash control and the fan works on all settings 1, 2 and 3.

I don't know the routing of these wires or how these two switches are wired, but I will guess the two are in parallel.

Any suggestions for troubleshooting the wiring with a multimeter?

Does anyone know if the wiring to the rear fan motor runs through the left side rocker channel where all the water collects, or from above under the headliner to the rear fan motor?