1150gs alternator upgrade.

otruk

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Hi Folks

My Denso 40 amp alternator has just split its casing at 210000 so I cant complain. Just rummaging through my draws (ohh) and have a Bosch 50 amp which fits, my issue being the wiring. The Denso has blue and green wire as well as the main red but the Bosh only has one fitting. I assume it would be the green wire for the Bosch as that supplies the ignition switch? And the blue seems to run charging light so would I leave that off or wire it to the green?

Thanks
 
Have a look at the wiring diagram in the Haynes….
Denzo
15= green ….seems to be the connection to the ignition switch +kill switch
61=blue
B+= red

Bosch
B+ red
D+ blue
 

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Thank you for that, on the Bosch unit I think it will be only the green I need, just not sure what to do with the blue or will it be spare?
 
Memory a bit vague but does the Denso not have a small sub harness that you unplug and plug the main loom connector into the Bosch altrrnator
 
The Denso unit has two small wires in a block connector and the Bosch has only one terminal. Its which one of the 2 wires I connect to the Bosch unit.
 
Fantastic thank you for that. :beerjug:
 
Just doing this! Got a Bosch alternator, there'a a Denso one fitted. I can see the Bosch connector further up the loom, it has a lug so it will only go in the alty one way. Theres 2 wires on the loom, but I can only see one pin inside the alty connector, is that correst. Do I need to swap over anything from the Denso unit?
Thanks again, Mike
 
jacksdad63 said:
Just doing this! Got a Bosch alternator, there'a a Denso one fitted. I can see the Bosch connector further up the loom, it has a lug so it will only go in the alty one way. Theres 2 wires on the loom, but I can only see one pin inside the alty connector, is that correst. Do I need to swap over anything from the Denso unit?
Thanks again, Mike
Click to expand...
The Two wires on the Bosch connector are for the Denso adapter lead which you have fitted.

When you connect the Bosch connector to the Bosch alternator. The connector will ensure the correct wire in the loom connects to the only pin on the alternator. For clarity this should be the blue wire, the green wire is not required for the Bosch alternator.

Additionally, there is No need to transfer anything across from the Denso alternator, everything is built into the Bosch alternator.
 
Ian J Hartley said:
The Two wires on the Bosch connector are for the Denso adapter lead which you have fitted.

When you connect the Bosch connector to the Bosch alternator. The connector will ensure the correct wire in the loom connects to the only pin on the alternator. For clarity this should be the blue wire, the green wire is not required for the Bosch alternator.

Additionally, there is No need to transfer anything across from the Denso alternator, everything is built into the Bosch alternator.
Click to expand...
Thats great news! I've looked at the Haynes wiring diagrams, the GS shows 2 wires, the RT shows just the one, and the Denso alty has 4 pins in the connector!
I paid £200 for the Bosch one, with 6 month warranty, yet the same seller has a Denso one listed at £600.... :oops:
 
Noooo...the pullies are different sizes! Can I swap them over?
The Denso one has a normal nut holding it on, the Bosch, smaller pulley, is some sort of damper in the centre and no nut, appears to have an internal torx or allen type fitting...don't ythink they are interchangeable after all
 
Last edited:
jacksdad63 said:
Noooo...the pullies are different sizes! Can I swap them over?
The Denso one has a normal nut holding it on, the Bosch, smaller pulley, is some sort of damper in the centre and no nut, appears to have an internal torx or allen type fitting...don't ythink they are interchangeable after all
Click to expand...
You ought to try at least….. (y)
 
jacksdad63 said:
Noooo...the pullies are different sizes! Can I swap them over?
The Denso one has a normal nut holding it on, the Bosch, smaller pulley, is some sort of damper in the centre and no nut, appears to have an internal torx or allen type fitting...don't ythink they are interchangeable after all
Click to expand...
The Bosch alternator with the 57.3mm diameter pulley uses the same belt as the Denso Alternator. 4PK592.

Provided the alternator fits physically and you can tension the belt, no need to change the pulleys. The rotation speed of the alternators are likely to be different, but that won’t matter provided the power output at lower rpm is achieved.
 
The original Denso pulley is 66mm where the belt sits, the Bosch is 54.5mm, so it may not be tight enough. I was wondering why there's just the one belt, the new continental says 5PK592 (611) and is identical to the old one...I'm lost now!
The BMW parts supplier has replied, says they aren't interchangable....
 
jacksdad63 said:
The original Denso pulley is 66mm where the belt sits, the Bosch is 54.5mm, so it may not be tight enough. I was wondering why there's just the one belt, the new continental says 5PK592 (611) and is identical to the old one...I'm lost now!
The BMW parts supplier has replied, says they aren't interchangable....
Click to expand...
There are. 2 sizes being used…
One is the 611 and the other is a 592.
The 592 is really almost too tight to get it on the GSA but the old one removed was a 592. (12.31.7681941)
Could work .?
F830A025-03D1-4051-AA1F-539CAA3577D2.jpeg
 
I can try the Bosch alty with the one wire, won't take long to fit it.
I've got the old genuine belt, as above, and a new Continental 4PK611 (592) ELAST
Its not easy is it!
 
Well its all working. Fitted the Bosch alty, plugged in the one connector and the live feed, then fitted the new Continental Elast belt, went on with just a little resistance, 'rolled it over a bolt' hack. Very easy yet tight enough, I suspect people who say its bloody hard work have the Denso alty with the slightly bigger pulley?
 
jacksdad63 said:
Well its all working. Fitted the Bosch alty, plugged in the one connector and the live feed, then fitted the new Continental Elast belt, went on with just a little resistance, 'rolled it over a bolt' hack. Very easy yet tight enough, I suspect people who say its bloody hard work have the Denso alty with the slightly bigger pulley?
Click to expand...
The 1100/1150 alternator is adjustable for belt tension ? It’s not fixed in place like the 1200. I always fit the 611 belt to 1150 bikes.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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