Bosch Alternator, tachometer connection?

[saltwater_gypsy]

I have a Bosch 55A alternator which has the existing connections made via a three pin block. There are also a further two unconnected terminals (one an M6 the other an M4). Which one is the tachometer connection?
I've surfed the net but no joy as alternator is circa 1982.
Thanks for any info.

 

[VicS]

If one is marked "W" thats the one.

No reason for it to be 6mm, that might be an earthing connection so its more likely to be the small one ..... asuming there is a tacho connection!

 

[saltwater_gypsy]

Thanks but there is no terminal marked "W"

 

[pvb]

Is there a terminal marked simply "+" (rather than B+ or D+)? If so, this is the tacho connection.

 

[VicS]

I would not have expected it to be marked + I'd have assumed that to be another connection to the rectified output for some auxiliary or control system but there is no standard marking for alternators.

If one of the others is marked AC that will be it. W and AC are the only markings I know of for the tacho connection.

There may not be a tacho output at all but you could try checking with an AC voltmeter to see if you can find an unrectified output.

Is it even one of those on the 3 pin connector. One is presumably the main output, one is the connection to the warning light but whats the third? (Some Bosch alternators from that era had external regulators that had a three wire connection. Its not on eof those is it?)

 

[iangrant]

Standard Bosch connections:

B+ (Big one) = Output
D- = -
D+ = Warning lamp
+ = 7 Volt connection (Tacho)


iAN