Battery selector switch

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J

Jim H SR

I have a Cat 27 and have a concern over selecting battery options while the engine is operating. The factory-installed switch(1979) has the 1, 2, ALL, and OFF positions. The engine is an Atomic 4 Gasoline with a 35 AMP alternator. With the engine operating at an idle, can I: Change from 1 to 2? Or 1 to ALL? Or 2 to 1? Or either 1 or 2 to ALL? Or any ther combinations? I KNOW I CANNOT SWITCH TO OFF WITH THE ENGINE OPERATING.
 
C

Chris Gonzales

NO

Don't change it. It can be left in any position but you cannot change it to a new position while the engine is running without damaging the diodes in the alternator.
 
G

Garry @ S/V TASHTEGO

Yes

A modern marine battery switch is a "make-before-break" switch. When shifting from one setting to the next, the connection will be made to the second terminal before the connection to the first terminal is broken. This is to assure that the alternator doesn't ever see an open circuit. You are correct that you can't turn the switch to OFF with the engine running but the others are OK. If you are unsure about your switch, hook a VOM to the output side of the switch with the engine off and watch the voltage as you switch from one position to the next. If the voltage drops to zero between settings (except when switching to OFF) then your switch is defective and should be replaced.
 
C

Chris Gonzales

The 5411 manual says.....

"To prevent alternator damage do not open or switch the battery circuits while the engine is running". I believe this also applies to the A4.
 
J

John Visser

Alternator field disconnect battery switch

There are switches available with an AFD feature (Blue Sea) that solves this problem.
 
B

Bob Camarena

Zapper

There's a product available called the Zapper (avail from West Marine and others). It's a small device that's designed to prevent the alternator from damage should you accidentally disconnect.
 
S

Sam

Selecting 1 or 2

I have the same set up on my Catalina 27 1977 and I have had no trouble switching between 1, 2, and all while engine is running.
 
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