vague Veglia

A

andre

Senior member
How's that - I found a fresh ignition related question...

My SFC1000 runs an electronic tacho and an IIS ignition.

The tacho has had a tendancy to get the needle waving way higher than actual revs when the turn signals are on. Since compulsory 'headlights on' laws, the tacho behaves even more erraticly. I've just had the tacho checked and they say it's working fine.

Any suggestions? Earthing of coils? JW?...

regards
Andre
 
Hello Andre,
                    Gee ask a tough question,  you have no pity for an ageing feeble mind like mine...  :)
nice of you to invite me for a response all the same.


    Covered the RGS et al instrument pod in the past posts on forums,  becomes lengthy in content as all the facets are covered, in required details.

    Perhaps easy things first,  being an IIS user the Veglia pod Tacho can be tested with test position "F" on the module.  This will tachometric drive the tacho from 1000rpm to 10,000rpm in 1000rpm increments,  time on each test 1K increment reduces with each successive step.  Any tendency for erratic needle movement or incorrect reading will be obvious. 

  Have tried several permutations of addressing this vexed problem of an automobile pod on a motorcycle implementation,  Laverda and Veglia in this case.  Key point is the limited life cycle of cars, mostly 10 years.  These pods are now in excess of 25 years old,  coupled to the severe environment of the RGS/A and am amazed the pods work as well as they do.

  The tacho movement drive chip or IC is a BA115 from memory,  and is non existent in the parts world.  Many is the tacho pcb have stripped of all original parts and installed a LM2917 charge pump device.  Also restoring the meter movement damping with stiction fluid Rocol Kilopoise ( spelling not checked ).  Improved overall accuracy is restored and available devices can be sourced as repair spares. 

  The original factory design was to send 300V spikes through the motorcycle harness to drive the tacho,  ok on cars mostly. Can be a source of severe electrical interference on the motorcycle,  even more so these days given additional load on the electrical system,  including heated clothing items,  ipods ( dangerous to my mind, need total concentration when riding ie personal view ),  or the more usual these days GPS item(s).

    The IIS can maintain the implemented factory 300 Volt drive for the tacho or it has a dedicated 12V drive signal to drive tacho's.  It does not always follow the BA115 chip will drive properly on a 12V signal.  The circuitry on the Veglia pcb, AC couples the 300V signal to a voltage divider,  which feeds the BA115 input pin.  Hope that makes sense.

  Try the easy things first Andre and let me know the result of test position F procedure,  as you see fit.  Unsure which tacho you have implemented,  most after market units can be switched for 300V or 12V drive.  Obviously care needs to be used when switching input signal conditioning.

  HTH and regards to all.  John.
 
mmhh - I am not half as experienced as John but if it only happens with turn signals on, I would assume there is a change in the signal due to the turn signal relay is giving pulses somehow into the tacho circuit. I would assume the only connection between the two should be - the earth side. Try to bridge the earth from the tacho directly back to the battery and see if this solves it. If not, try bridging the earth of the blinkers directly to the battery or a separate plus-feed for the IIS?!? Witt describes similar issues with the DMC but more regarding an impulse initiated by the coils going into the plus feed coming from the main key switch that cause irritation on the DMC itself. Maybe the relais is to close to the tacho-feeding cable?

Not sure if the fault could happen through this and if you could solve it this way, but it would be the way I would check it by separating the two circuits.

Just my
2centvorne.jpg
 
Hello Lothar,
                      Nice to meet you once more.

  You make good suggestions about this anomalous tacho and or wiring problem.  As i read Andres' report he indicated a staged problem,  mis operation of the tacho when headlight is on and or flasher circuit in operation.  Indeed your on the money,  it would appear to be return or earth issues,  however it may be one or more issues at play.  The only indicator of a problem is the tacho behaviour.  With ignition on and motor not running, Andre can test the tacho for proper operation  as described in my last post. If that test is a success,  then he can turn his attention to wiring and the possibility of impedance issues in supply or return paths.  Voltage gradients cause many strange outcomes on motor vehicles.  Once more you have a good idea to break the problem in the middle if possible. Degraded wiring and connectors are going to be more common with the Laverda's now, most rate a "Grandpa" status.

  The IIS wiring harness has a return wire, that  is attached to the battery negative terminal direct.  Personally i do not use any of the steel frame as a conductor.  Reasons are many,  for instance, not impressed by DC currents travelling through the steering bearings when the "earth" wire fails or not connected in the headlight shell,  mostly on 180 Laverda's.

  Regards from John. 
 
John, Lothar
cant say my mind any less aged/worn than yours John.
Slight indication is that I 'forgot' my SFC has a DMC2. You should have remembered my Motodd has the IIS John... It's operating just peachy by the way.
Tacho has been tested and works fine.
My speciality is Road building and even I managed to come up with earthing as the next issue guys. The SFc is fairly stock but I will go over the earth connections.
Nice to hear you both anyway...

Respectful and warm regards,
Andre
 
yeah - and think of a separate plus cable, too. It is described in the manual that there might be some issues if you use the same plus feed that comes from the key lock, as it supplies all other things, too. Maybe use a relay that is turned on by the red wire coming from the key lock and give it a direct supply from the battery...

Oh - and yes, hello John! Good to see you back online, longtime no hear!  ;) Hope all is well with you.
 
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