Elect HONDA CIVIC 1996 6.G Workshop Manual

- How the Circuit Works
'96198 Models
The air delivery system directs the flow of air used
by the heater and air conditioner systems.
Mode Selection
Mode selection is controlled by the mode switches
in the heater control panel and the mode control
motor. When you select a specific mode, voltage is
applied through the dimming circuit to the LED,
which comes on, indicating the mode selected.
Ground is orovided to the mode control motor
though that mode switch. The motor then runs until
the air control door reaches the proper position.
Fresh/Recirculation 56lection
When you press the fresh or recirculation button, a
ground signal is sent from the heater control panel
to the recirculation control motor. The motor then
runs until the recirculation door reaches the proper
position. Battery voltage is also applied through the
dimming circuit to the corresponding LED, and the
LED comes on.
Refer to the Service Manual (Section 21, Heater) for
specitic tests or troubleshooting proc€dures.
'99J00 Models
The heater control panel receives battery voltage at
all times through fuse 47. With the ignition switch in
ON (ll), voltage is supplied to the heater control
panel through fuse 17. The control panel is
grounded at G402.
The heater control panel controls the air delivery
motors, and supplies a 5 VDC reterence voltage to
the air mixture control motor.
The air mixture and mode control motors each
receive inputs trom the heater control panel. The air
mix motor regulates the mixture of cold and hot air
by varying the position of the heater-evaporator doot
The mode control motor controls the direction and
volume of outlet air. The air flow can be directed to
the dashboard vents or the corner vents.
Both the air mixture control molor and mode control
motor are grounded by the h€aler control panel.
The recirculation control motor receives battery
voltage through fuso 17 when the ignition swilch is
in ON (ll). lt regulates the position of the fresh/recirc
door, and is controlled by two position inputs from
the heater control panel ("Recirc" and "Fresh").
Refer to the Service Manual (Section 21, Heater) tor
specific tests or troubleshooting procedures.
61-3

Rear Window Defogger
- How the Circuit Works
'96198 Models
Voltage is applied at all limes through tuse 50 to the
rear window detogger relay (contacts). With the
ignition switch in ON (ll), voltage is applied through
tuse 16 to the rear window defogger switch.
When you turn the switch ON, voltage is applied to
the defogger timer circuit. The timer circuit supplies
voltage to the rear window defogger relay (coil). The
relay energizes and supplies voltage to the rear
window defogger. The defogger grid then heats the
rear window to remove any condensation from the
glass.
The defogger timer circuit will automatically turn off
the rear window defogger after about 25 minutes.
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
'99100 Models
Voltage is applied at all times through fuse 50 to the
rear window delogger relay (contacts). With lhe
ignition switch in ON (ll), voltage is applied through
fuse 16 to the heater control oanel.
When you turn the rear window defogger switch
ON, a signal is sent to lhe defogger timer circuit
built-into the heater control oanel. The timer circuit
supplies voltage to the rear window defogger relay
(coil). The relay energizes and supplies voltage to
the rear window defogger. The defogger grid then
heats the rear window to remove anv condensation
from the glass.
The defogger timer circuit will automatically turn otf
the rear window defogger after about 25 minutes.
Refer to the Seryice Manual (Section 23, Electrical)
for specific tesls or troubleshooting procedures.
64-2
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Integrated Control Unit
NOTE: Fuse 31 is hot with lgnition Switch in START (lll) and clutch pedal depressed or A,/T Gear Selector in
PARK (P) or NEUTRAL (N), see Starting System, page 21,21-1, ot 21-2.
See BrakeSystemlndicatorli^hl
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Brake System Indicator Light
- '96-'98 Models
NOTE: Fuse 31 is hot with lgnition Switch in START (lll) and clutch pedal depressed or A,/T gear selector in
PARK (P) or NEUTRAL (N), see Starting System, page 21 , 21-1, or 21-2.
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- '99-'00 Models
NOTE: Fuse 31 isJtot with lgnition Switch in START (lll) and clutch pedal depressed or A,,/T gear selector inPARK (P) or NEUTRAL (N), see Starting System, page 21 ,2i-1, ot 21-2.
UNDER"DASHFUSEiRELAYBOX
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71-1

Brake System Indicator Light (cont'd)
- How the Circuit Works
The brake system indicator light comes on to alert
the driver that the parking brake is applied, or that
the brake fluid level is low. lt also comes on as a
bulb test when the engine is cranked.
Parking Brake
With the ignition switch in ON (ll) or START (lll),
voltage is applied through fuse 25 to the brake
system light. When you apply the parking brake, the
switch closes and provides a ground for the light.
The light then comes on to remind you that the
parking brake is applied.
Brake Fluid Level
With the ignition switch in ON (ll) or START (lll),
voltage is applied through fuse 25 to the brake
system light. lf the brake fluid level is low, the brake
fluid level switch closes, providing ground to the
circuit. The brake system light then comes on,
alerting the d verto a low brake fluid level in the
brake master cylinder. (Check brake pad wear
before you add fluid).
Bulb Check
With the ignition switch in START (lll) and clutch
pedal depressed or A'lT gear selector in PARK (P)
or NEUTRAL (N), voltage is applied through fuse 31
to the brake bulb check circuit. The brake bulb
check circuit closes, allowing current to flow through
the brake system light and bulb check circuit to
ground. The brake system light then comes on to
test the bulb.
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
71-2
a
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How the Circuit Works
Seat Belt Warning
With the ignition switch in ON (ll) or START (lll),
battery voltage is applied to the seat belt reminder
light. When the seat belt is not buckled, the seat
belt reminder/key-on beeper circuit in the
integrated control unit senses ground through the
closed seat belt switch. The seat belt reminder light
comes on and stays on, and the beeper beeps for
6 seconds. The reminder light and beeper will stop
when the seat belt is buckled or the timer circuit
deactivates them.
lgnition Key Warning
Battery voltage is supplied at all times to the seat
belt reminder/key-on beeper circuit in the
integrated control unit. When you turn on the
ignition key switch the integrated control unit
senses ground. lf you open the driver's door, the
door switch closes, causing the beeper to sound
until the door is closed.
Refer to the Service Manual (Section 23, Electrical)
for specitic tests or troubleshootrng procedures.
73-1

How the Gircuit Works
All Except GX
Do not smoke while working on the fuel system.
Keep open flame away trom the work area. Drain
fuel only into an approved container.
A thermistor is mounted in the fuel tank unit. When
the thermistor is cool, its resistance is very high.
When the thermistor's temperature increases, its
resistance decreases. Fuel in the fuel tank transters
heat away lrom the thermistor fast enough to keep it
cool so the thermistor's resistance stays high and
lhe low fuel indicator light does not come on. When
the fuel level drops below the thermistor, the
thermistor's temoerature increases. Without the fuel
to cool it, the thermistor's resislance decreases,
allowing current to llow through the low fuel
indicator light and the thermistor to ground, and the
low fuel indicator light comes on.
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
GX
The PCM turns on the low fuel indicator light when
the fuel level is low. The PCM will also blink the
indicator light when a problem is detected by the
fuel tank pressure sensor or the fuel tank
temperature sensor.
Refer to the Service Manual GX Supplement
(Section 11 , Fuel and Emissions) for specific tests
or troubleshooting procedures.
74-1

Gauges (cont'd)
- How the Gircuit Works
When the ignition switch is in ON (ll) or START (lll),
battery voltage is supplied through fuse 25 to the
gauges in the gauge assembly.
Speedometer and Odometer
The odometer and soeedometer drive circuits
receive pulses from the vehicle speed sensor
(VSS). The pulse rate increases as the car
accelerates. The frequency and duration of these
input pulses are measured and displayed by the
speedometer, odometer and tripmeter.
Tachometer
The tachometer drive circuit receives pulses from
the ignition control module (lCM) in the distributor
assembly or the ECM/PCM. The solid-state
lachometer then displays these pulses as engine
speed. For each 200 pulses per minute from the
ignition control modul€ (lCM) or the ECM/PCM, the
tachometer displays 100 RPM.
Engine Coolant Temperature Gauge
The engine coolant temperature gauge has two
intersecting coils wound around a permanent
magnet rotor. Voltage applied to the coils, through
fuse 25, generates a magnetic lield. The magnetic
field, controlled by the coolant temperature sending
unit, causes the rotor to rotate and the gauge
needle to move. As the resistance in the sending
unit varies, current through the gauge coils
changes. The gauge needle moves toward the coil
with the strongest magnetic field.
The 6ngine coolant temperature sending unit's
resistance varies from about 137 ohms at low
engine temperature to between 3H6 ohms at high
temperature (radiator fan running).
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
81-2
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Fuel Gauge (All except cX)
The fuel gauge has two intersecting coils wound
around a permanent magnet rotor. Voltage applied
to the coils, through tuse 25, generates a magnetic
field. The magnetic field, controlled by the fuel
gauge sending unit, causes the rotor to rotate and
the gauge needle to move. As the resislance in the
sending unit varies, current through the gauge coils
changes. The gauge needle moves toward the coil
with the strongest magnetic field.
The fuel gauge sending unit's resistance varies
from about 2-5 ohms at full, to about 110 ohms at
empty. When you turn the ignition switch off, the
gauge remains at the last reading until you turn the
ignition switch to ON (ll) or START (lll) again,
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting procedures.
Fuel Gauge (GX)
The fuel gauge has two intersecting coils wound
around a permanent magnet rotor. Voltage applied
to the coils, through fuse 25, generates a magnetic
field. The magnetic field, controlled by the PCM,
causes the rotor to rotate and the gauge needle to
move. The PCM calculates the gas quantity in the
fuel tank by using the fuel pressure value detected
by the tuel tank pressure sensor and the fuel
temperature value detected by the fuel tank
temperalure sensor, and outputs the signal to the
gauge assembly. The gauge needle moves toward
the coil with the strongest magnetic field.
When you turn the ignition switch off , the gauge
remains at the last reading until you turn the ignition
switch to ON (ll) or START (lll) again. When the
PCM detects a malfunction with the fuel pressure or
temperature, or detects a gas leak, the PCM
reduces the fuel meter to 0.
Refer to the Service Manual GX Supplement
(Section 11 , Fuel and Emissions) for specific tests
or troubleshooting procedures.
a
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A/T Gear Position Indicator (conrd)
- How the Circuit Works
With the ignition switch in ON (ll) or START (lll),
voltage is applied to the A,/T gear position indicator.
The A,/T gear position switch provides a ground for
each position. As an input is grounded, its indicator
light comes on. lf you select R, for example, ground
will be provided to the input of the A,/T gear position
indicato( and the R indicator will come on.
With the headlight switch in PARK or HEAD, voltage
is applied to the RED/BLK wire terminal. This
changes the indicator panel illumination from fixed
to controlled by the dash lights dimmer input
through the RED wire.
When the powertrain (all except '96-'98 CVT) or
transmission ('96198 CVT) control module (PCM or
TCM) detects an abnormality in the automatic
transmission control system, or when you request
diagnostic trouble codes through the service check
connector, the PCM or TCM will make the D4 (D for
CVT) indicator light blink.
Refer to the Service Manual (Section 14,
Automatic Transmission) for specific tests or
troubleshooting procedures.
\ia
89-2