Fuse, Switch, resistor, motor.
In order of ease to check, you already checked for power at the motor - so next check the fuse for power on both sides (installed) - then look for power at the resistor pack & lastly the switch (just 'cause it's hardest to access).
FWIW, a good procedure with the meter is to test a known good 12v. source, to make sure you've got a good ground & the meter is working/set right.
Just hooking to metal doesn't always work due to ungrounded parts or poor connections. (getting fooled is easy, getting dependable results takes some effort)