Buick LeSabre 1965 Service Manual page 638

1 0 - 6 8 SPEEDOMETER
ELECTRICAL SYSTEMS
(d) To eliminate the tank unit tan
wire which runs through body to
connector at frame rail, remove
the left kick pad and unplug wir-
ing harness connector. Contact
brown wire in connector with red
wire of test unit, ground test unit
and turn ignition switch on. If the
dash unit functions properly with
movement of test u n i t arm,
trouble was caused by the brown
wire.
2. Test of Dash Unit
(a) Disconnect wiring connector
under left kick pad. Attach test
unit red wire to connector tan
wire leading to dash unit; attach
test unit black wire to ground.
(b) Make sure multiple connector
at instrument cluster is plugged
in securely.
(c) Turn ignition on. Move arm
of test unit up and down against
stops. If dash unit pointer moves
freely from " E " to "F" with
movement of tester arm, dash
unit is okay. If pointer does not
move or only moves part way,
printed circuit may be defective,
dash unit may not be grounded
properly, or dash unit may be
faulty.
(d) B e f o r e removing complete
instrument cluster to c h e c k
printed circuit, try replacing dash
unit with a known good unit.
(e) If pointer of new dash unit
will not move properly with
movement of tester arm, printed
circuit is probably defective. Re-
move instrument cluster assem-
bly as described in paragraph
10-48, b.
3. Test of Tank Unit.
(a) If • tests given above indicate
that the trouble is in the tank
unit, check the tank unit wiring
and if necessary, remove the unit
so that it may be cleaned and
tested. Tank unit is accessible
f r o m under car ( e x c e p t in
Rivieras).
(b) A f t e r thorough cleaning of 1. Jack up rear wheels in a safe
tank unit, connect it to ground
and to wire leading to dash unit,
and test in the same manner as
when using tester. If tank unit
tests okay it should be reinstalled
in tank, otherwise, it should be
replaced with a new unit. When
installing tank unit make certain
that insulation is folded over the
terminal and snapped over wire.
1 0 - 5 2 SPEEDOMETER
a. Speedometer Heads
The speedometer head has a mag-
netic speed indicator and a gear
driven odometer. It is driven by
a flexible cable connected to a
worm gear in the transmission
rear bearing retainer.
The speed indicating portion of
the speedometer operates on the
magnetic principle. There is a
permanent magnet in the speed-
ometer head which rotates at the
same speed as the cable. This
magnet exerts a pull on a speed
cup causing it to move through an
arc in direct ratio to the revolving
magnet speed. A pointer is at-
tached to the speed cup spindle
to indicate speed on the speed-
ometer dial. A calibrated h a i r
spring (part of speed cup) opposes
the magnetic pull on the speed
cup so the pointer indicates speed
accurately; this spring also ro-
tates the cup and pointer to zero
when the car stops.
Some speedometers have a trip
odometer and a reset knob. Push-
ing the reset knob in and turning
clockwise gives a quick reset to
zero; turning the knob counter-
clockwise r e s e t s t h e t r i p
odometer 1/10 mile at a time.
Speedometers which have the trip
odometer also have either the
safety b u z z e r or t h e cruise
control.
b. Checking Noisy
Speedometer
manner and close car windows to
exclude outside noises.
2. With transmission in direct
drive, run slowly from 0 to 50
MPH and back to 0, noting speed
range where noise appears.
3. Apply brakes and shift trans-
mission to park position, then run
engine through same speed range
as before.
4. If the noise continues even
with the transmission output shaft
stationary, something other than
the speedometer installation is
at fault.
5. If noise disappears with trans-
mission stationary, check further
for cause of noise by checking for
p r o p e r installation of speed-
ometer cable as shown in Figure
10-71 or 72.
6. If cable installation is okay,
next remove inner cable from
casing. Lay inner cable on clean
paper to keep dirt from cable
lubricant. Reconnect empty casing
to speedometer and recheck for
noise at various speeds. If noise
still continues, noise is coming
from transmission rather t h a n
from speedometer or cable.
7. If noise stops with inner cable
removed, speedometer or cable
is at fault. Inspect cable as de-
scribed in subparagraph c.
c. Inspection of Speed-
ometer Cable and Casing
If t h e speedometer installation
appears to be noisy or the speed
indicator wavers, inspect the ca-
ble casing for d a m a g e , sharp
bends, or for being out-of-position
in the supporting clips. See Fig-
ure 10-71 or 72. If casing is in
good condition and properly in-
stalled, remove inner cable for
inspection.
1. Disconnect c a b l e casing at
speedometer head, then pull inner
cable out of upper end of casing.
2. Inspect cable for worn spots
or breaks. Check cable for kinks