Sunbeam ALPINE I SERIES: APLINE II SERIES, Workshop Manual

Page: 358 / 413

5th
re-issue
Page 40
ELECTRIC IMPULSE TACHOMETER
{Refer to Fig. 37)
Later Models
Fitted as standard equipment on later models is the
electric impulse tachometer, this instrument Is an
advanced
engine-speed
indicator which measures
revolutions per minute by "counting" electrical
Impulses called for by the Ignition coil.
The tachometer has no mechanical take-off and
operates In the following manner:-
The tachometer "counts" low-tension current
impulses demanded by the Ignition coll by means
of a transistorised printed circuit unit contained
within the instrument head. This In turn Influences
8rowiv'
Yellow
.,_ ____ CONTROL BOX
IGNITION
WARNING LIGHT
white
3
I
2�4
IGNITION AND
STARTER SWITCH
ROOTES MAN UAL WSM. 124
Section N (Elec. Equipment)
a D.C. voltmeter movement to which a pointer Is
attached, so that when the engine Is running this
moves round the instrument dial which is cali­
brated from 0-6,000 r.p.m. The accuracy of this
instrument is not affected by variations in Ignition
timing, or gap settings of either the distributor or
the plugs.
No servicing is required of the tachometer, there­
fore, where the Instrument becomes faulty, a new
instrument must be fitted as the unit can only be
repaired by the manufacturers or their appointed
agents.
Should the Instrument cease to function, a check
is to be made of the electrical connections to see
if they are in order. If the connections prove to be
correct, then the tachometer must be removed
and replaced by a new unit.
Fig. 37.
Tachometer and circuit dia1ram. (Earth wire
on
tachometer head for Rapier only.)