Engine is off but the blower fans are still running full speed. Where is the fuse to pull.

Check the AC fan relay
Symptoms Of A Defective Blower Motor Relay
The blower motor relay's job is to basically bypass the current that passes thru' blower motor resistor and deliver it directly to the blower motor. With the blower motor getting full battery current, it'll run in HI speed.

The most common symptom you'll see, when the blower motor relay fails in your Chevy S10 (GMC S15), is that the blower motor will not run in HI speed (but will run in LO, M1, and M2 speeds).

In some cases, the blower motor will fail and the blower motor will not run in HI but you'll have all of the other speeds working.

https://easyautodiagnostics.com/gm/2.8L/blower-motor-relay-multimeter-test-1

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First check the fuse in the fuse box .
It also depends on witch fan /engine cooling fan /Blower motor fan.
Engine fans will have a relay more so then a blower motor .
The differences is this the blower draws more power and runs on a different ckt then the engine controls .So you can use the blower motor with out the engine running key on .
You don't say witch one you are having the problem with so I will try to explain both .
Most of the time both have relays and fuse's .The heater fan works on HI only off the relay so the relay is good if it works on HI.
The relay for the fan to cool the engine is different it controls all speeds do to temp change its cold some times has to handle more information .The relay the one thing they both have in common is the connections tend to get corroided Most of the time you can unplug and clean the plug in connectors to fix the issue

check fuse first
then scan PCM , oops you didnt and the BCM does run this stuff.
so not scanning it , you miss all those FACTS.

the blower is dead. (aka , not spinning , or silent)
on all cars made the answer is the same.
blown fuse, fuse marked BLower, is blown. LOL.
controls not turning it on, controls failure.
blower bad. (motor) hot wire it in place to test)
wires to any of the above.
or the resistor block bad, (if it works on high but not low)
i have the schmematic in hand.

the HVAC relay pulls in by command of the BCM
the relay then sends 12vdc power to the blower via fuse 41
the blower is now hot full time.
the blower then needs a ground to spin (run)
on high, the ground G601 via the speed knob,switch makes that ground connection, so if the fan dont spin and say the fan is ok
then the relay is not closing or the fuse 41 is blown. (why not look at the fuse first for all electric fails)
the BCM sees you, turn fan on, (heat or cold)
and closes this relay, on the left.
if the relay does not close, (and coil is ok inside)
the the BCM didnt see those HVAC requests.
use a scan tool and look for BCM errors..>??????

The resistor bank is bad for slow speeds, the switch is bad for high speed. In your test, you have voltage, but the switch wont carry the amps, to run high speed. Open circuits will not blow fuses. Replace both switch and resistor bank for all speeds. Make sure to clean leaves and trash from fan housing and see if fan spins freely.

read this post on what's causing blower motor to run all the time.

http://ricksfreeautorepairadvice.com/blower-motor-wont-shut-off/
Blower motor wont shut off Ricks Free Auto Repair Advice

The blower motor doesn't use a different fuse depending on the speed. The most common cause for your concern is bad blower motor resistors. The resistors lower the voltage to the blower motor so it doesn't turn at full speed when you have it set to fan speed 1. When the resistors blow out the only setting that works is full speed because it doesn't go through the resistor.

THE FAN BLOWER RELAY IN STUCK CLOSE POSITION.YOU HAVE TO REPLACE FAN BLOWER RELAY.

in the duct work where the blower motor attaches you will see the resister block. it is held into the duct work with two or three screws and there is a wiring going to it. undo the screws and pull it out carefully and replace it. your fan should work fine after that. be careful if the circuit is live as it does heat up alot.

does it turn off when the car turns off? if so, you probably need a new blower motor resistor. They run about $80 but shop around. Fixed my problem right away

The Highest fan speed is applied through a relay that is part of the resistor assembly, and the fuse provides unswitched 12-volts to the relay. The relay contacts are most likely welded closed, causing the blower to run on high whenever the fuse is in play. If you feel lucky, you might give the relay a rap with a tool handle to try and dislodge the contacts. If this is successful, you may use the blower as normal until the problem re-occurs, as it probably will. The only real solution is replacement of the relay/ resistor.