Acura Integra 1998 Service Manual page 1500

Gauges (cont'd)
- How the Circuit 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 speedometer drive circuits
receive pulses lrom 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 ('98-'99 Models)
The tachometer drive circuit receives oulses from
the ignition control module (lCM) in the distributor
assembly. The solid-state tachometer then displays
these pulses as engine speed. For each 200 pulses
per minute from the ignition control module (lCM),
the tachometer displays 100 RPM.
Tachometer ('00 Model)
The tachometer drive circuit receives pulses f rom
the PCM or ECM. The solid-state tachometer then
displays these pulses as engine speed. For each
200 oulses oer minute trom the PCM or ECM the
tachometer displays 1 00 RPM.
Engine Coolant Temperature Gauge and Fuel
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 field. The magnetic
field, controlled by the engine coolant temperature
gauge 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 tield. The fuel gauge
works the same way.
The engine coolant temperature gauge sending
unit's resistance varies from about 137 ohms at low
engine temperature to between 30-46 ohms at high
temperature (radiator fan running).
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 to LOCK (0), the
gauge remains at the last reading until you turn lhe
ignition switch to ON (ll) or START (lll) again.
Refer to the Service Manual (Section 23, Electrical)
for specific tests or troubleshooting
procedures.
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