If you can’t hear any change from low to high blower, I would first look at the switch. I believe the low/high differentiation is in the switch. Do a continuity test on the switch and check the ohmic values between low and high.
I don’t have any tech info on the blower motor. I would look for the data plate on the motor, get the manufacturer’s address and ask for technical advice.
I have copied the parts of the service manual below.
DESCRIPTION
The blower is mounted in the aft fuselage section and is connected to the overhead vent system. The
blower draws air in from dorsal fin or from left hand side of fuselage on s/n 28-8011001 and up and forces it
through ducting- A four position blower switch on instrument panel controls the blower.
REMOVAL OF BLOWER ASSEMBLY
l. Remove access door from aft wall of baggage area.
2. With master switch OFF, disconnect plug assemblies at blower assembly.
3. Remove inlet and outlet hoses from blower assembly by removing clamps.
4. Remove screws, washers, and nuts securing blower assembly to hanger braces.
5. Remove screws and washers securing blower assembly to retainer and hangers.
6. Remove blower assembly from aircraft.
DISASSEMBLY OF BLOWER ASSEMBLY
1. Remove hose duct from forward edge of blower assembly by removing nuts, washers, and screws.
2. Remove cover from blower assembly by removing nuts, washers, and screws.
3. Remove blower fan from motor shaft by removing set screw.
4. Remove motor as follows:
a. Separate plate from motor cover by carefully drilling out connecting rivets.
b. Cut motor wires at edge of receptacle and plug, and remove wire ends from blocks.
c. Remove motor from mounting plate by removing nuts, washers, and bolts.
REASSEMBLY OF BLOWER ASSEMBLY
1. Mount motor on plate and secure it with bolts, washers, and nuts. Be sure that motor nuts are snug and
the shaft spins freely.
2. Position cover over motor plate with motor wires protruding through cover grommet.
3. With holes in cover matching holes in motor plate, secure two parts together with rivets.
4. Apply PRC-5000 sealant to fill any opening left after wires are brought through grommet.
5. Install wires in plug and receptacle.
6. Position blower fan on motor shaft and secure with set screw.
7. Secure cover to blower assembly with screws, washers, and nuts.
8. Position hose duct on blower assembly and secure it with screws, washers, and nuts. Screws must be
installed with their heads inside duct.
9. After cleaning surfaces of all old sealant, use PRC-5000 sealant to seal duct to blower assembly.
INSTALLATION OF BLOWER ASSEMBLY
1. Position blower assembly in hangers and retainer and install washers and screws.
2. Install nuts, washers, and screws securing blower assembly to hanger braces.
3. Seal all hose joints with Arno number C-520 wrap tape. Install inlet and outlet hoses. Secure hoses
with clamps.
4. With master switch off, connect plug and receptacles at blower.
5. Check blower for proper operation.
6. Install access door to aft wall of baggage area and secure with attaching hardware.
You can check the power out of the switch at the motor; according the to manual the power wire for the ground is AC26A in the aircraft harness; the black wire in the aircraft harness is low speed; the white in the harness is medium speed and the red is high speed.
The connections to the motor (M) from the aircraft harness (H) are:
brown (M) to AC26A (H);
Yellow (M) to black (H)
Red (M) to white (H)
Orange (M) to red (H)
