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Buell Forum » Old School Buell » Archive through June 22, 2008 » Speedo facts nobody told me... « Previous Next »

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Werewulf
Posted on Sunday, June 08, 2008 - 12:41 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

ive been crying the blues about my no worky speedometer, ever since i converted my 99 S-3 to a carb...it was working fine when i started the project and upon initial fire-up, the needle never moved again....now i found this http://www.badweatherbikers.com/buell/messages/384 2/10307.html it looks like the sensor works off of 5 volts, that i guess is reduced by the ecm... well, i have no ecm.....so, im guessing that im shooting 12 volts thru the sensor and it can only handle 5... am i wrong??? if so, maybe i have fried my sensor... then i must buy a rewiring kit... if so, does this kit remove the voltage from the ecm to a 12 volt source, or what... come on now, we have some electronic wizards around here, help to understand this...
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Oldog
Posted on Sunday, June 08, 2008 - 01:06 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

check with Reepicheep, the speed sensor is indeed 5v and yours is dead.
one of our electronic whizzies could cluge up a voltage divider I hope that your meter is not fried.
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Reepicheep
Posted on Monday, June 09, 2008 - 11:27 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The tuber sensors were fed battery V+. In theory this was fine, I think we found a spec sheet for the hall effect semiconductor like the one used in the sensor, and it was rated for like 14 volts.

In practice though, these are CMOS devices, which can be killed by *really* short transients. And on the tubers, they frequently were. Thats why some bikes ate them one after another, some bikes never touched them.

There are probably a lot of reasons for the spikes, including bad grounds and failing charging systems, that in theory could be resolved, but the bottom line is that the sensor needs regulated input.

I think the new part re-routes the +v to come from a regulated source, or you can just put in a regulator... I can hook you up with one if that works a lot better for some reason, but the factory method is probably a little more reliable (it does not introduce new parts that have to be weatherproofed and attached).
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