Bosch K1 wiring

[Geoff W]

Hi all,

New to this forum.  I’m re-installing an original Bosch K1 alternator on one of my Cummins 6BT 210hp engines (its regulator was replaced).  The start key activates the volt meter and a light with buzzer on the dash.  There is a separate push button to activate the starter motor.

I connected the alternator as follows: battery positive cable to B+, start key wire to D+, tacho wire to W terminal and ground wire to alternator chassis.  When I turn the start key there is a short that immediately blows the fuse in the circuit that has the starter solenoid on it.  With only the B+ and ground wires connected it also blows the fuse.  I replaced the fuse with the same result.  There are fabric washers isolating the B+ and D+ wires from the chassis – I can’t see any cracks or faults in those.  

Observations:

With all wires disconnected from the alternator and start key ON but engine *not* running:  Cable from battery shows 13V, wire from start key shows 13V, ground wire shows 8V.  The first two make sense but why would the ground wire have 8V? 

With all wires disconnected: There is no circuit (infinite resistance) between terminal B+ and ground post.  There is also no circuit between terminal D+ and ground post.  

Any input on likely cause of the short circuit would be appreciated.  

Thanks in advance, Geoff. 

I found and read another post on this topic but couldn’t resolve based on information there.  

Topic

[Tony Athens]

Wiring diagrams are posted on the web site

[Author]

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