Alternator Swap

[Neil W]

Due to uprating my 1150gs to include heated grips and a few other electrical extras I have swapped the alternator from a smaller Denso one to the larger output Bosch one ( I've had a spare altenaot from a 2000 mile 2003 model lying in the garage for ages.
The swap was simple but the wiring is a bit confusing, the Denso alternator has one large terminal (B) to which the red wire attaches (same as the Bosch one), but on the Denso one the other terminal (D) has a two wire connector attached (green/blue), the Bosch one has one blue wire attached to its (D) terminal.
HOW DO I WIRE IT UP?
t

 

[Greg Masters]

The red wire goes to the biggest terminal. On the wiring diagram this is marked X9241on both alternators. Essentially, this goes straight to the +ve terminal of the battery (although it is routed via the starter motor).

If I'm reading the circuit diagram correctly, you should have a spare green wire. DO NOT CONNECT THIS TO THE ALTERNATOR. Pop a voltmeter on this wire and measure the voltage to earth. Should be 0 volts with ignition off and 12 v with ignition on.

Do you also have a blue wire in the loom?

Greg

 

[Neil W]

Yes, I have an old 1100 loom lying and the blue wire on it and my 1150 both have the same female spade connector on (the one that goes on the D terminal of the Bosch alternator).
On the 1150 , however, it then plugs into the T shaped double block connector (which has the green wire as its other terminal) for the Denso alternator via a short wire.
A sticker on the Denso alternator shows a small representation of this T shaped block connector, the blue wire terminal is marked as L and the green wire terminal is marked as IG ?

 

[Greg Masters]

It'd be helpful if you just checked the voltage on the green wire as per my earlier post. If it is as I think it is then:

• Connect the blue wire in the loom to the small terminal on the Bosch alternator
• Blank off the green wire - you don't need it - but don't forget that it's 'live' with the ignition on.

BTW - I think L means warning light and IG means ignition.

Done.

Greg

 

[johnhorsley5]

On the subject of swapping alternators,
I have Denso unit fitted, but bought a Bosch as a spare.
The diagrams suggest different part numbers for the Bosch belt and the Denso belt.
If/when I swap alternators, do I need to get a different belt and is the pulley different? Can the pulleys get swapped?