February 28, 1961
Bulletin No. SB-831
Electrical System
(Supplement to SB-813)
SUBJECT: Charging batteries while connected to junction boxes
of alternator equipped engines.
Paragraph 3.b. contained in Service Bulletin No. SB-813 has already cautioned you
about being careful with battery polarity (battery cable connections) when working
with alternator equipped engines. Briefly, if the battery is connected to the
junction box with reversed polarity (battery cable connections reversed), the
rectifiers will conduct full battery current and may be damaged before the 60-amp.
generator fuse burns out. If the ignition switch is "ON" while polarity is reversed,
the voltage regulator will also be damaged.
A similar danger exists when recharging batteries while they are connected to the
junction boxes of alternator equipped engines. Since accidentally connecting the
charger to the battery with reversed polarity is very easily done, the safest
possible procedure to protect the 60-amp. fuse, and possibly the rectifiers, should
the fuse fail to opportunely "blow", is to disconnect the battery from the junction
box BEFORE connecting the charger. Disconnection is most conveniently accomplished
by disconnecting the cables from the battery terminals.
The alternator system is rugged and efficient, has few moving parts subject to
wear and is capable of charging at low engine speeds. For this reason, under normal
operation and with all components of the generating circuit functioning as intended,
recharging batteries should be an infrequent necessity. However, batteries may
nevertheless require recharging as the result of customer forgetfulness in turning
off ignition switches, accessories or lights. We therefore urge you to advise your
customers, particularly the do-it-yourself variety, about exercising reasonable
care in connecting battery and charger cables.
Keep in mind that blown 60-amp. generator fuses or damage to voltage regulators
and rectifiers caused by reversed battery or charger cable connections is not
damage which is attributable to faulty material, parts or factory workmanship.
JOHNSON MOTORS
W. W. DeWees
Service Department
WWD:eb
NOTE: Post on your V-75 index.
