Help wiring a Broan Heat/Vent/Light
Since the three switches &amp; devices are all in one circuit, they need to share hot (panel to the switches) and neutral (from the devices back to the panel).
Hot
Take the hot wire off the vent switch. Typically there is a jumper/bridge connecting the two hots (i.e., to make a common hot connection) on the double switch. Assuming that is the case, connect two short pieces of black wire with a wire nut to the hot wire that you removed from the vent switch. Connect one of those pieces to the vent switch and the other to the double switch (heat or light screw, doesn't matter which one).
If there is no jumper/bridge between the two hots on the double switch, then connect three short pieces of black wire with a wire nut to the hot wire that you removed from the vent switch. Connect on to each of the 3 switches (vent, heat &amp; light screws of double switch).
Neutral
Based on your diagram, you appear to be using either separate wires in conduit or a /4 cable - black/white/red/blue, and joining the two separate neutral connections of the HVL together to the white (neutral) wire going back to the panel. If so, that's fine.
However, if you actually have two separate cables - one black/white from vent switch and one black/white/red from the double switch then you have a bit of a problem. Each neutral in a cable has to match the loads in the cable. Based on the diagram, the light &amp; vent (which each typically use &lt; 100W) share a neutral and the heat (typically ~ 1500W) has its own neutral. You can't mix &amp; match neutrals. Either they all get combined and the neutral wire runs next to all the switched hot wires in conduit or in a single cable, or then must be kept matched together. To keep them matched together in cables, the white (neutral) for the light &amp; vent must be together with the switched hots for those devices and only combined together with the heat's neutral in the switchbox - not combined at the device.