Shootist touched on what I was thinking. On my setup, I have two heaters on the rear pump loop. If you have boiler fluid going through heating the heater, then the thermostat is calling for heat. The bedroom fan always operates but the bathroom fan is on a separate switch and can be turned off if you don't want the bath overheated. You may have something like this in your unit.
Also, the type coach and the particular controller for the Aqua Hot may help. For instance, on my digital controller there are 5 inputs for thermostats and fans. Only 3 inputs are used, so if there is a defect on one input, you may be able to switch the wires to a different input and have all the same functions.
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2019 Fleetwood Discovery LXE 40M w/2021 Equinox
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