Something I found (Different chassis, different body builder) is sometime the fuse charts are ignored by the body builder. The HEVAC system is not a "Chasis" item but a body builder item So on my rig there were 3 fuse boxes that applied to the "Vehicle" side of life (which includes the dash HEVAC) and sure enough one of the panels had fuse labeled "heater" or Air Conditioner (forget which)
That was not where the body builder hooked the lead (I eventually found out where and fixed the issue but it was not easy) Was not the only thing they screwed up.
Tool you can use is a TEST LIGHT.. this looks a bit like an old fashion ice pick (Works like one if you need an ice pick) but the handle is clear or translucent with a light builb inside and a wire with a clip lead.
For this test the test lamp beats the (Explative omitted) out of a multi meter for you test the fuses IN SOCKET and about one fuse every 2 seconds.
Clip the lead to a known good ground.
Most Vehicles these days use blade fuses. in each "End" of the fuse is a "Window" of sorts.
Now first touch the tip to a known battery source.. Bright good. often I have to re-seat the lamp.
Touch each window Ignition in a position that the blower should blow.
BRIGHT BRIGHT good fuse
DARK DARK no test this fuse does not have power (It's also not the fuse you want)
Bright Dark or Dark bright... DING DING DING you found it.
