BSA D14/4 BANTAM SUPREME D14/4 BANTAM SPORTS, Workshop Manual

Page: 93 / 120

D14/4 ELECTRICAL SYSTEM G7
FIG. G4. Lighting switch continuity test.
Finally there should be no circuit between any
switch pin and earth (earth body) in any switch
position selected.
Premature Bulb Failure
Premature bulb failure involving all or many of the
light bulbs at one time on a full D.C. battery system is
caused by a defective connection in the battery "line."
The following should be checked:—
(1) Battery positive terminal.
(2) Battery negative terminal.
(3) All connections in the four-hole connector into
which the battery negative lead is fitted.
(4) Rectifier earth lead (translucent).
(5) Harness frame earth.
(6) Both ends of the short link wire in ignition
switch joining brown lead from lighting switch to
brown lead from main body of harness.
(7) Check battery acid level and top-up if necessary.
Contact Breaker
Check the contact breaker points gap and adjust to the
recommended setting of ·012", as detailed on page
B17. Check cleanliness of contact faces, these, if in
good order, should have a light grey frosted
appearance. Where fine matter,
e.g., oil and grease
have been present, the contacts may have a blackened,
burnt appearance. Should the condition not appear
serious, then a light application of fine grade emery
will restore them. If in doubt replace the whole
breaker unit. Check the action of the breaker arm on
the pivot, as any sticking of this arm can cause
intermittent difficulty.
On no account should the star-shaped retaining
washer on the breaker arm be removed from the
pivot as the amount of end float is strictly
controlled, and is essential to the correct
functioning of the contact breaker.
Condenser
Should the capacity be suspect, first check for good
contact to earth and security to the contact breaker
plate. Secondly, a quick check can be made for short-
circuit to earth; the battery and bulb is a simple and
quick test, but first remember to disconnect from the
contact breaker plate. Visual recognition of a defective
condenser or its connections is vivid blue arcing at the
contacts when an attempt is made to start the engine or
when the engine is actually running.
Where an Avometer is available, a more conclusive
check can be made. This is done by firstly,
disconnecting the condenser lead from the contact
breaker. Select the Avometer to the ohms by 100
range and, using the test prods from the meter, connect
one to the condenser lead and the other to the
condenser case. The needle on the Avometer will
move rapidly and return to infinity immediately.
Remove the test meter prods and wait fifteen seconds.
Re-apply the prods and the needle should not again
move. If it does the condenser requires replacement. It
should be noted that a very small white spark across
the contact breaker points when running is normal.