R1100gs alternator belt

[West coast gser]

Hmm ,went to change the alt belt on my 1100 today got the front cover off after a faff cos o the crash bars ,anyhoo I was surprised to find my engine doesnt have the oil breather pipe .. well slackened off the alt n had a look @ the belt looked ok n no worn parts tho there was a bit o dust in there presume from the belt ..whipped it off and fitted the new one but cant fro the life of me torque the bolt to 7nm ..it seems very tight so just backed it off a touch ..re assembled it n fired it up ..no noises or slipping/chirping tho the battery light is on till you blip the throttle then it goes out ..is that normal ? with a new belt fitted ..it did it with the old belt fitted aswell ..have I done something wrong ? thought once the new belt was fitted the light would go out as soon as the engine fired up ..?? cheers

 

[Paul G (BHT)]

If the RPM is slightly low the charging light won't go out until the throttle is blipped, once the alternator 'kicks in' the light should stay out even if the revs are allowed to drop.

 

[West coast gser]

If the RPM is slightly low the charging light won't go out until the throttle is blipped, once the alternator 'kicks in' the light should stay out even if the revs are allowed to drop.

thanks .. thats what its doing ... didnt fancy having to take off the crash bars n move the tank back again ..

 

[mouthfulloflake]

a slightly larger wattage bulb in the dash board where the battery light is will bring the alternator online and charging faster.

 

[moonhead911]

a slightly larger wattage bulb in the dash board where the battery light is will bring the alternator online and charging faster.

so yours saying if you change the bulb in the dash to a larger watt. it will make the alternator charge faster is that correct ?

 

[mouthfulloflake]

Yes Sir,

the circuit to excite the field winding of the alternator goes through that bulb, larger wattage will have have it charging faster.
BMW actually specified a larger bulb somewhere along the line. ( looking at parts fiche it looks like the bulb went from 1.7 watts to 3 watts)

look here, and follow D+ from the charge/warning light ( blue wire)

 

[mouthfulloflake]

That D+ terminal is also a good place to connect a relay for AUX light ( or anything else)
that you only want to be powered up while the engine is running, very easy to make a "Y" pigtail with connectors and not modify the stock wiring.

 

[moonhead911]

as far as i know once the alternators been excited is disconnects from that circuit?

 

[mouthfulloflake]

sort of, it doesn't really disconnect, but there is no longer potential there to light the bulb ( as long as the alt is working)

think of a positive going to a positive( alternator works and becomes voltage source), rather than a positive going to a negative ( alternator not working) which would light the bulb.

 

[moonhead911]

the bulb my have changed from 1.7 to 3 watt so did the alternator some use a bosch alternator 50 amp some use a denso 40 amp so that might be the reason the change in dash bulbs?

 

[mouthfulloflake]

No idea from me, on that Moonhead.

here is some more info on the theory of operation though

http://www.lotuselan.net/forums/elan-archive-f16/alternator-warning-lamps-etc-t10387.html

 

[moonhead911]

iv just never seen or header of changing the bulb to improve charging performance. can any one ells comment on this..
much appreciated

 

[mouthfulloflake]

its not "improving" anything

just exciting the alternator's field coils sooner, for instance if you have to rev the throttle to get the light to go out, a larger wattage bulb would likely remedy that.

 

[moonhead911]

ok i just thought you meant it would charge faster. usually if to start the bike using the fasts idle / choke the bike will rev that high to turn the light of and power the alternator up