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TACHOMETER (Synchromesh and Jetaway)
The tachometer can be removed for service
by removing the bezel retaining screw located at the rear of
the tachometer housing. After removing the attaching screw,-
pull the tachometer outward to disconnect the bulb, feed and
ground wire.
Before replacing a tachometer, the following
tests should be performed:
INOPERATIVE TACHOMETER
- Check the tachometer ground connection by
connecting a jumper wire to a good ground and holding the other
end against the tachometer bezel. If the tachometer will now
operate, a defective ground is indicated and must be corrected.
- Check for loose connections or broken wire
from the ignition coil to the console. Repair if necessary.
- Check the tachometer fuse located inside
the console by replacing it with a known good fuse. (AGA-2 amp.)
- If the tachometer is still inoperative, remove
it from the console. After removal inspect the connector and
ground wire at the back of the tachometer for loose connections.
Repair if' necessary.
- Connect a jumper wire between the terminal
of the tachometer and the negative side of the coil. Connect
another jumper between the tachometer ground and a good ground
on the car. Start the engine and observe tachometer operation.
If the tachometer now operates, the trouble is not in the tachometer
assembly and Steps I through 3 must be rechecked to locate the
trouble.
- If the tachometer is still inoperative, it
must be replaced.
INACCURATE TACHOMETER
If the tachometer is inaccurate, it must be
calibrated against a known accurate tachometer, such as one used
in engine tune-up work. Calibration is performed as follows:
- Remove tachometer from console.
- Remove calibration hole cover (brass plug
or tape) from back of tachometer case.
- Connect jumper wire between the terminal
of the tachometer and the negative side of the ignition coil.
Connect another jumper between the tachometer ground and a good
ground on the car.
- Start the engine.
- Accelerate engine to 2000 rpm indication
on the tune-up tachometer.
- Insert a small screwdriver through the hole
and into the adjusting slot, turn the screwdriver slowly until
the tachometer reading agrees with the tune-up tachometer.
- Vary engine rpm from idle to 2000 rpm. Electronic
tachometer indication should be smooth throughout range of operation
and comparable to the test tachometer.
- Replace the hole cover.
- Turn off engine, disconnect jumpers and install
tachometer. Make sure all connections are tight and electrically
secure.
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