Chapter 22 Basic Electrical Tests 353
Figure 22-26. Example of how voltage drops can be used to check internal resistances without disconnecting components from a
circuit. A—The branch of the resistor pack for the lowest blower speed shows a high voltage drop and a high resistance. B—The
branch of the resistor pack for medium blower speed has a medium voltage drop and a medium resistance. C—The branch of the
resistor pack for high blower speed must have low resistance to pass high current. The voltage drop is also low.
A
B
C
LO
OFF
MED
HI
Lower blower speed
8 V drop
high resistance
Blower switch Resistor pack Blower
motor
LO
OFF
MED
HI
Medium blower speed
4 V drop
medium resistance
Blower switch Resistor pack Blower
motor
LO
OFF
MED
HI
High blower speed
0 V drop
no resistance
Blower switch Resistor pack Blower
motor
~V
OFF
V
Ω
mA
mA
A
~
8.00V
~V
OFF
V
Ω
mA
mA
A
~
4.00V
~V
OFF
V
Ω
mA
mA
A
~
0.00V