1998 HONDA CIVIC Block

How To Use This Manual
Symbols
Ground - "G"
This symbol means the end ol
the wire is attached (grounded) Ito the car frame or to a metal I
part connected to the frame. \i oro,|
-t'
Each wire ground (G) it --/
numbered for reference.
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Switches
These switches move
together; the broken straight
line between them means the,
are mechanically connected.
Other types of switches are
controlled by a coil or a solid
state circuit. Unless otherwise
noted. all switches are shown
in their normal (rest) position,
with power off.
This ground symbol (dot
and 3 lines) overlapping the
component means the housing
of the component is grounded
to the car frame or to a metal
part connected to the frame.
This symbol represents
the bus inside a ground
connector. The dots I
i:l*,':1,'^:*,:"
;"
r"L I I I
terminals connect to.
The ground symbol (large dot)
is the connection between the
bus and metal (grounded) part
of the car.
Terminals - "T"
ffi
ffi
Solid-state
Fuses
This means power is supplied
when the ignition switch is in ON (ll).
Current rating
Diodes
A rectifier diode works like a one
way valve. lt allows current to
llow only in the direction of the
arrow.
A Zener diode blocks reverse
current at normal voltages just like
a rectifier diode. At high voltages.
however, a Zener diode allows
current to f low in reverse
oo
Each "T" lerminal (ring type)
is numbered for reference and
location. A "T" terminal is
secured with a screw or bolt.
Shielding
This represents RFI
(Radio Frequency
Interference) shielding
around a wire. The
shielding is always
connected to ground.
f--l;j-i",..
I
,,,,
T

- How the Circuit Works
Battery voltage is supplied through tuse 56 to the
A,/C compressor clutch r€lay contacts at all times.
With the ignition switch in ON (ll), vollage is applied
to the coil of the A,/C compressor clutch relay
through fuse 17. When you push the A,/C switch
ON, and the heater fan switch is in position | , 2, 3,
or 4, a "ground" input is provided to the engine
control module (ECM) or powertrain control module
(PCM) through the l'lC thermostat and the l'lC
pressure switch.
The A,/C compressor clutch relay is grounded by the
engine control module (ECM) or powertrain control
module (PCM). When energized, the A'lC
compressor clutch relay allows battery voltage to
turn on the A,/C comDressor clutch.
The A,/C ON indicator light comes on when the A,/C
system is requested.
A,/C Thermostat
The A'lC thermostat is located on the evaoorator
housing. The A,/C thermostat turns off the A,/C
compressor clutch if the temperature at the
evaporator goes below 3'C (37'F). This prevents
condensation from freezing on the evaporator fins
and blocking the air delivery into the passenger
compartment. The blower motor will keep running
when the sensor turns off the comDressor.
A,/C Pressure Switch
The fuC oressure switch is located in the condenser
outlet line where refrigerant is in a high
temperature/high pressure liquid state. The switch
will sense abnormally high or low pressure, and
open the circuit. This removes ground, and the
compressor will stop running.
Thermal Protectot
The thermal protector, located on the A,/C
compressor, opens and turns the compressor off if it
senses high temperature. Once the compressor
cools, the switch will close and the compressor will
begin running again.
Refer to the Service Manual (Section 22,
Air Conditioning) for specific tests or
troubleshooting procedures.
62-3

- How the Circuit Works
Radiator Fan
Voltage is provided at all times to the radiator fan
relay (contacts) through fuse 57. With the ignition
swilch in ON (ll), voltage is provided to the coil of
the relay through luse 17.
The radiator tan relay can be grounded through
either the engine coolant temperature switch or the
engine control module (ECM) or powertrain control
module (PCM).
The engine coolant temperature switch grounds
the radiator fan relay (coil) when the engine
coolant temperature exceeds 199'F (83'C). The
switch opens when coolanl temperature
decreases 3'- 8'C.
Condenser Fan
Voltage is provided at all times to the condenser fan
relay (contacts) through fuse 56. With the ignition
switch in ON (ll), voltage is provided to the coil of
the relay through fuse 17. When you push the A'lC
switch and put the heater fan switch in 1, 2,3, o( 4
position, the ly'C thermostat comes on, the
condenser fan relay energizes, and the condenser
fan motor runs.
A,/C Thermostat
The A,/C thermostat is located on the evaporator
housing. The A,/C thermostat tums off the A/C
compressor clutch if the temperature at the
evaporator goes below 3'C (37'F). This prevents
condensation from freezing on the evaporator fins
and blocking the air delivery into the passenger
compartment. lf the temperature goes below 3'C
(37"F) tuming off the Ay'C thermostat, ground will be
removed from the condenser fan relay. This will
deenergize the relay and remove voltage from the
condenser fan motor causing the fan to stop running.
Reter to the Service Manual (Section 23, Eleckical)
for specific tests or troubleshooting procedures.
63-3