system. The hybrid ECU and battery temperature sensors
control the operation of the blower.
Hybrid refrigerant cooling routes R-134a refrigerant
through a separate evaporator located next to the power
control module or battery pack. The refrigerant flow
cools the evaporator, as well as the hybrid components.
Hybrid Dash Display
A combination meter or cluster in the dash of a
hybrid displays many variables pertaining to the perfor-
mance and condition of the gasoline engine and electric
drive system. The combination meter contains the
speedometer, odometer, fuel gauge, engine gauges,
hybrid power display, and the hybrid drive ready light, as
well as several warning lights. One design is shown in
Figure 38-21.
A hybrid power display in the combination meter
informs the driver of the hybrid drive operating condi-
tions. Many hybrid displays will indicate when the elec-
tric “assist” is working, how electrical energy is being
used, and how much energy remains in the battery pack.
The power display often reads in kilowatts (Kw) of power
output from the HV battery pack. This display helps the
driver utilize and recapture as much energy as possible
while driving.
A hybrid drive ready light often blinks when you
press the brake pedal and turn the ignition key to the start
position with the gear selector in park. When the electric
drive is engaged, the ready light glows continuously to let
you know the vehicle is ready to be driven.
A hybrid master warning light in the combination
meter warns if there is a problem in any part of the drive
train. If the hybrid ECU detects any abnormal condition
in the electric drive circuitry or related components, it
will illuminate the master warning light to notify the
driver that something is wrong.
A battery pack warning light in the combination meter
illuminates if the battery’s state of charge is below normal
limits. This could be caused by leaving the key on too long
when parked, running the air conditioning too long on bat-
tery pack energy, a shorted battery pack, or a circuit problem
preventing the battery pack from being recharged normally.
A conventional malfunction indicator light (MIL) turns on
when any ECU detects a vehicle malfunction.
Hybrid Service Safety
Modern gas-electric hybrid drive systems generate
enough electrical energy to cause electrocution. It takes
only a couple amps of current flowing through your body
to stop your heart and kill you. Most hybrid vehicles con-
duct almost 600 volts ac and 300 volts dc at hundreds
of amps. By comparison, home wall outlet voltage is
120 volts ac.
Remove Jewelry
Remove all jewelry when working on a hybrid’s
high-voltage circuits. It is very easy for a metal watch to
short between a high-voltage conductor and ground since
high voltage can arc through the air and into the jewelry.
Chapter 38 Hybrid Drive System Operation and Repair 709
Figure 38-21. The hybrid dash display will provide information about the mode of operation and the condition of the electric portion
of the drive train. (Toyota)
Discharge
warning light
Malfunction
indicator lamp
Master warning
light
HV battery
warning light
Ready light