Replacement Alternator 09 GSA

Steppers. Just seen this post and now looking at your collection of Denso scrap

Are they all spilt in the same place? In your shots all the split cases seem to be along a bore for the casing bolt. Wondering if in fact it's the bolts that rust, then crack open the cases which locks up the rotation?

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Slipperyeel said:
Steppers. Just seen this post and now looking at your collection of Denso scrap

Are they all spilt in the same place? In your shots all the split cases seem to be along a bore for the casing bolt. Wondering if in fact it's the bolts that rust, then crack open the cases which locks up the rotation?

Sent from my SM-G975F using Tapatalk
Click to expand...

They all crack in the same place as it's the weakest point.
 
They fit the Bosch alternator to the RT and the Denso Alternator to the GS. Which is slightly odd.

So given that the pulley size and the belt size are the same on both bikes and alternators (according to the Parts guide)

What’s there to stop fitting a Bosch instead of a Denso? I’m assuming the alternator mounting to the frame are the same or similar which would only leave the electrical to sort out.......?
 
The alternator on my 2012 GSA has been deteriorating over the last few years and finally seized up a few weeks back.

Ended up going for a Bosch one, although required a minor wiring mod. Brian at BGM reckoned it was exceptionally rare he'd seen issues with the Bosch version, but the original were seizing fairly frequently with age.

Still, not bad for 144k. it would probably have been nearer 170k if I'd still been commuting over the last year...
 
So in order to convert an R1200GS with a Denso Alternator to run on a Bosch Alternator which is standard fit to the R1200RT range then a slight wiring modification needs to be performed on the R1200GS.

According to the wiring diagrams the theory is thus:-

Does anyone who has performed this modification disagree with the theory.
 

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Ian J Hartley said:
They fit the Bosch alternator to the RT and the Denso Alternator to the GS. Which is slightly odd.

So given that the pulley size and the belt size are the same on both bikes and alternators (according to the Parts guide)

What’s there to stop fitting a Bosch instead of a Denso? I’m assuming the alternator mounting to the frame are the same or similar which would only leave the electrical to sort out.......?
Click to expand...

Pulley size is also different between a GS and the ADV ... as seen in the picture. Simply undo the pulleys and swop them over .. Motorworks used to supply a wiring kit to fit a Bosch in place of a Denso. Also the wiring that plugs into the alternator is it’s self a short section, about 3inches long, which plugs into the main loom.
 

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You can see the short alternator loom. The white alternator connector plug is at one end and the green and blue wire is attached to the plug that connects to the loom.
 

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Steptoe said:
Pulley size is also different between a GS and the ADV ... as seen in the picture. Simply undo the pulleys and swop them over .. Motorworks used to supply a wiring kit to fit a Bosch in place of a Denso. Also the wiring that plugs into the alternator is it’s self a short section, about 3inches long, which plugs into the main loom.
Click to expand...


Steptoe said:
You can see the short alternator loom. The white alternator connector plug is at one end and the green and blue wire is attached to the plug that connects to the loom.
Click to expand...

Thanks for all that Neil......:thumb2

Given the problems with the Denso, I just can’t understand why anyone would replace like for like, particularly when there is a better more robust option available. I certainly wouldn’t.

At least a used Bosch would likely be better than a new Denso, which would be my choice.

Some Useful knowledge. Thanks again.
Ian
 
It definitely seems like a no brainer.

But I've still got a question about the pulley diameter, which will presumably alter the rpm of the unit, though I'm unclear what kind of differences it would make? I mean, does an RT rev lower than a GS?

Btw, I'm also not sure what the difference in diameter is between the two (which had the larger/smaller).

As mentioned above, seems odd they would fit an entirely different unit to the GS??

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Slipperyeel said:
It definitely seems like a no brainer.

But I've still got a question about the pulley diameter, which will presumably alter the rpm of the unit, though I'm unclear what kind of differences it would make? I mean, does an RT rev lower than a GS?

Btw, I'm also not sure what the difference in diameter is between the two (which had the larger/smaller).

As mentioned above, seems odd they would fit an entirely different unit to the GS??

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Click to expand...

As far as I can gather looking over the model range of the R1200GS /ADV/ RT from 04 through to 13 there were several permutations of alternators. The earlier models had a different crank shaft pulley, so this might explain why there are different size alternator pulleys.

There were 2 types of Denso and 2 types of Bosch alternators fitted through the range, so you would need to be careful which Bosch you should use.

Example:-
For a 2010 R1200GS Adventure with a standard Denso Alternator, the Bosch alternator would have to be from a R1200RT (2010) part No 12317715081 Bosch No 0 124 120 015. The Crankshaft pulleys and V belts are the same size on both models.

Ian
 
This might help with the understanding of interchangeability, not withstanding that need to slightly alter the electrics when converting from Denso to Bosch.
 

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The short alternator loom for a Denso.
 

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Hi Chaps,

I have just completing a full service on my bike and have noticed that I have a cracked alternator, yes it is a Denso!. I am looking around and from what I have seen the way to go is to fit a Bosch one from an RT.

These are the points that I am looking for help with before I start buying the wrong thing
Find a used Bosch alternator from a 2005 RT - or will later ones work as well
So looking at the great info provided above I will need to cut the existing plug off the loom and solder a new plug on that will connect to the Bosch unit. and from the wiring diagram it looks like we only need the one wire.

Remove the pulley from my Denso and fit that to the Bosch?
or
Can I just use a shorter belt?

I would rather just fit a shorter belt as removing the pulley does not sound that simple

Cheers
 
waggy said:
Hi Chaps,

I have just completing a full service on my bike and have noticed that I have a cracked alternator, yes it is a Denso!. I am looking around and from what I have seen the way to go is to fit a Bosch one from an RT.

These are the points that I am looking for help with before I start buying the wrong thing
Find a used Bosch alternator from a 2005 RT - or will later ones work as well
So looking at the great info provided above I will need to cut the existing plug off the loom and solder a new plug on that will connect to the Bosch unit. and from the wiring diagram it looks like we only need the one wire.

Remove the pulley from my Denso and fit that to the Bosch?
or
Can I just use a shorter belt?

I would rather just fit a shorter belt as removing the pulley does not sound that simple

Cheers
Click to expand...

It would help if you told us what bike you have...?
 
Hi,

Sorry about that I should know this but by now! 2004 GS ON A 55 plate. Also it looks like the Bosch unit is used on a 2006 GSA as well as the RT and they have the same bottom pulley size as mine.

Cheers
 
waggy said:
Hi,

Sorry about that I should know this but by now! 2004 GS ON A 55 plate. Also it looks like the Bosch unit is used on a 2006 GSA as well as the RT and they have the same bottom pulley size as mine.

Cheers
Click to expand...

Choose the simplest path. A used Bosch alternator should come with it’s pulley already attached. So at the very least all you would need would be a different belt. As you have to remove the belt anyway to fit the replacement alternator, changing the belt isn’t an additional problem.

You probably won’t have to modify the electrics. If you have the Denso adaptor cable fitted, then all you need to do is unplug it from the main electrical harness connector and then the harness connector should plug straight into the Bosch alternator.

You won’t need the external Zenor diode and bracket which the Denso uses with the Bosch alternator, so it can be removed as part of the change over.
 
Hi Ian,

Thank you for the quick reply. That is now a plan for me to work to. I think I have found an alternator, I have a new belt but it is the wrong size but I will have a chat with them to see if they will swap it for the shorter one. As the bike is in bits (the front subframe has just been powder coated) I will be able to take a good look for the adapter but if memory serves me right I am sure I have not seen one.

Cheers David
 
Hi, just checked and unless the connector is within the loom I do not have a separate Denso adapter which is a shame. Going to order a repair plug so that I can plug the Bosch in. Or Do you know the type of plug that it uses or just get the repair plug?
 
waggy said:
Hi, just checked and unless the connector is within the loom I do not have a separate Denso adapter which is a shame. Going to order a repair plug so that I can plug the Bosch in. Or Do you know the type of plug that it uses or just get the repair plug?
Click to expand...

I don’t sorry, but I’m sure someone might know. Most of the modern connectors are pretty much standard across multiple platforms.
 
@waggy how did you get on with this conversation and what mods did you have to do with the wiring and what belt did you use? Cheers.
 
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