1969 Scrambler electrical issues

[TedsDucs]

Hey Scrubs -

My name is Ted - recent lurker and now looking for help. I have been restoring a 69 Scrambler and have gotten to the fun part where I put it all back together. Here's the situation. When I got the bike, it did not have a battery, so in my excitement when I got it home, I immediately grabbed the first battery I could find - from a riding lawnmower - and hooked it up to test electrics and see if I had a spark. What I only realized later was that it was a 12V battery I was introducing into a 6V system....Ooops! Anyway, the lights did work - very bright, by the way!. Now, after the rebuild, and I hooked up the correct 6V battery, all I get is immediately blown fuses.

I do have a wiring diagram - thank you very much, Motoscrubs contributors, for the online info and manuals - I have traced everything I can. I did find a few chafed wires in the headlight bundles - what a rat's nest in there! - but can not seem to find a likely culprit for the short.

So, my big question is - Did I fry the regulator and/or coil when I hooked up that 12V battery? I did try to kick it a few time to look for a spark...Any good tricks to test the regulator or coil with a meter? I'm not an electrical genius, but I can follow directions....

Thanks for any input.

Regards, Ted

BTW, if you have time to kill and are interested, I am sporadically doing a blog of the restoration as a way to document it, here...

http://tedsducatis.blogspot.com/2013/03 ... on-hi.html

[JimF]

Hi Ted,

Your restoration is beautiful. Let's get it on the road.

Since your motorcycle is blowing fuses, I would begin there. The act of the fuse blowing is telling you there is likely a "short" circuit on the wire leading away from the fuse or there is a remote chance the fuse is just undersized. It may or may not not be your only problem, and it may or may not be your biggest problem, but it is a problem and needs fixing eventually. Since it is a problem that is waving its hand so-to-speak, it should be easy to find.


Before you start to look for a short circuit, keep in mind that most of your working circuits (lighting and ignition) have very low resistance "loads" on them which make the circuits look shorted when they are in working condition. An incandescent light bulb has a filament between between two contact points, and that filament is nothing more than a piece of wire which resembles a short. An ignition circuit has a coil on it which is just a very long piece of wire wound in circles many times. That wire resembles a short but it isn't one.


If you are working on a lighting circuit and trying to find a short it may help to take out the small light bulbs on the circuit for testing purposes, or in the case of the headlight to disconnect it. On the ignition circuit it may help to disconnect the primary winding from the circuit where you are looking for a short.


As for the 12-volt battery, I would be surprised if that 12 volts of potential was high enough to fry the regulator. Don't rule it out, but I think you should not pursue it just yet.


Can you tell us what electrical loads are on the circuit that is downstream of the fuse, and what size fuse is blowing?


Jim

[ducwiz]

Hi Ted,

on http://i.minus.com/ibepAKwCOCJ4eh.jpg you can download a simple test direction for the regulator, which I had written many years ago. Don't hesitate to ask, if you have questions about that. The DUCATI works directions are stored under http://ducwiz.minus.com/mYjSS1vWQ.
However, I'm afraid you've killed the regulator ...
Are you sure you had connected the battery the right way (negative ground) in each case?
The ignition coil can be tested by measuring the ohmic resistance of primary and secondary windings. If your ohmmeter reads 2-3 ohms for the primary, 5000-7000 ohms for the secondary, it is very likely the coil has survived.
On http://ducwiz.minus.com/ you can find more info stuff about Ducati singles.

cheers/good luck

Hans / Germany

[DewCatTea-Bob]

[quote="TedsDucs"
" My name is Ted - recent lurker and now looking for help. "

____ Welcome to our DUCATI-Single w.site Ted !



" the first battery I could find -
- and hooked it up to test electrics and see if I had a spark. What I only realized later was that it was a 12V battery I was introducing into a 6V system.... "

____ Connecting-up a 12-volt battery should only have one somewhat instant undesired effect (after the key-switch is turned-on), and that would be fairly short 6v.lightbulb-filiment life,, meaning that if the 12v.battery had been fully charged-up, the lights would've then burned-out within minutes after becoming powered-up.
However if the battery was low on stored power-juice, the 6v.lights's rather high current-draw would've then likely caused the battery's voltage-level to drop-down to perhaps under 10-volts,, which then would've made life a bit easier for the light-bulbs, (providing that your 12v.battery wasn't too large to be much affected by such a connected load).



" the lights did work - very bright, by the way!. "

____ Lights will indeed be overly bright whenever powered by excessive voltage/power, but they won't last very long that way... So either you didn't leave your lights turned-on for very-long, and/or your 12v.battery wasn't charged-up to it's normal storage-capacity.



" after the rebuild, and I hooked up the correct 6V battery, all I get is immediately blown fuses. "

____ That really OUGHT-to have nothing to do with having previously hooked-up any 12v.battery !
__ WHAT "fuses" are blowing ? _ And do you mean ALL/separately-installed fuses (in their separate fuse-locations), or merely-just multiple replcement-fuses in just one fuse-holder/location ?
Also, do you have all your fuses wired-up same as factory-stock ?



" I have traced everything I can. I did find a few chafed wires in the headlight bundles - what a rat's nest in there! - but can not seem to find a likely culprit for the short. "

____ Do your fuses blow whenever you simply connect-up the battery ? _ Or do they blow only after you turn-on the key-switch, or light-switch ?
__ IF only-just the fuse that's intended for just the main-lights blows only whenever the light-switch is turned-on, then I'd be most apt to suspect that one of the two power-circuits to the headlight-socket is out-of-place & finding a short-circuit to the HL.ground-circuit.
If so, then that likely wiring hook-up error should be checked-out.



" Did I fry the regulator and/or coil when I hooked up that 12V battery? "

____ The ign.coil should still be okay, even after many hours of running with 12-volts ! _ As it would then only become a bit warmer than normal when running at a higher than specified voltage.
__ The stock w-c.regulator is set-up to be non-functional without first being 'turned-on' by a 6v.battery with a minimal-charge. _ Your 12v.battery no-doubt fulfilled that requirement,, however I rather doubt that even if it had been FULLY charged-up (to 13.8v), could it have possibly compromised any of the regulator's internal circuity. _ (I'd expect it's related turn-on circuit to hold-up against at-least 24-volts before possibly surcoming to being overpowered.)
The rest of the stock w-c.type reg.box's internal-circuity is relatively independent of the battery, so I'm fairly sure that YOU haven't impaired it (with the 12v.battery connection).



" I did try to kick it a few time to look for a spark... "

____ And-so what did you see then ? _ (As there's no [stock] fuse for the ign.circuit.)



" Any good tricks to test the regulator "

____ With the use of an ohm-meter,, (then just-like as with a r/r.box with a fried-out rect/reg.circuit*), the meter's read-out should be near infinity regardless of set probe-polarity (between r/r.box-ground & either of it's two yellow-terminals), UNTIL the r/r.box's brown-terminal is fed with near 6-volts of positive-DC.
(* The stock (r/r.box)- units' internal-circuity is well-known to commonly be rather easily fried-out/burned-up if ran for very-long after the battery has become disconnected.)


Hopeful-Cheers,
-Bob

[TedsDucs]

Thanks for the replies, guys.

I am away from home right now, but will go back and try to trace the wiring to the fuses that are blowing. I have one on the positive lead from the battery that was blowing, and also one inside the headlight. They both heat up and go when I turn on the ign key. No effect from the light switch. I also have to recheck the headlight, as I'm afraid I did already blow that and need to replace it. Stay tuned - update when I get home and also go back through and make sure I don't have any more bad connections and put a meter on the regulator.....

Thanks, Ted

[quote="TedsDucs"
" My name is Ted - recent lurker and now looking for help. "

____ Welcome to our DUCATI-Single w.site Ted !



" the first battery I could find -
- and hooked it up to test electrics and see if I had a spark. What I only realized later was that it was a 12V battery I was introducing into a 6V system.... "

____ Connecting-up a 12-volt battery should only have one somewhat instant undesired effect (after the key-switch is turned-on), and that would be fairly short 6v.lightbulb-filiment life,, meaning that if the 12v.battery had been fully charged-up, the lights would've then burned-out within minutes after becoming powered-up.
However if the battery was low on stored power-juice, the 6v.lights's rather high current-draw would've then likely caused the battery's voltage-level to drop-down to perhaps under 10-volts,, which then would've made life a bit easier for the light-bulbs, (providing that your 12v.battery wasn't too large to be much affected by such a connected load).



" the lights did work - very bright, by the way!. "

____ Lights will indeed be overly bright whenever powered by excessive voltage/power, but they won't last very long that way... So either you didn't leave your lights turned-on for very-long, and/or your 12v.battery wasn't charged-up to it's normal storage-capacity.



" after the rebuild, and I hooked up the correct 6V battery, all I get is immediately blown fuses. "

____ That really OUGHT-to have nothing to do with having previously hooked-up any 12v.battery !
__ WHAT "fuses" are blowing ? _ And do you mean ALL/separately-installed fuses (in their separate fuse-locations), or merely-just multiple replcement-fuses in just one fuse-holder/location ?
Also, do you have all your fuses wired-up same as factory-stock ?



" I have traced everything I can. I did find a few chafed wires in the headlight bundles - what a rat's nest in there! - but can not seem to find a likely culprit for the short. "

____ Do your fuses blow whenever you simply connect-up the battery ? _ Or do they blow only after you turn-on the key-switch, or light-switch ?
__ IF only-just the fuse that's intended for just the main-lights blows only whenever the light-switch is turned-on, then I'd be most apt to suspect that one of the two power-circuits to the headlight-socket is out-of-place & finding a short-circuit to the HL.ground-circuit.
If so, then that likely wiring hook-up error should be checked-out.



" Did I fry the regulator and/or coil when I hooked up that 12V battery? "

____ The ign.coil should still be okay, even after many hours of running with 12-volts ! _ As it would then only become a bit warmer than normal when running at a higher than specified voltage.
__ The stock w-c.regulator is set-up to be non-functional without first being 'turned-on' by a 6v.battery with a minimal-charge. _ Your 12v.battery no-doubt fulfilled that requirement,, however I rather doubt that even if it had been FULLY charged-up (to 13.8v), could it have possibly compromised any of the regulator's internal circuity. _ (I'd expect it's related turn-on circuit to hold-up against at-least 24-volts before possibly surcoming to being overpowered.)
The rest of the stock w-c.type reg.box's internal-circuity is relatively independent of the battery, so I'm fairly sure that YOU haven't impaired it (with the 12v.battery connection).



" I did try to kick it a few time to look for a spark... "

____ And-so what did you see then ? _ (As there's no [stock] fuse for the ign.circuit.)



" Any good tricks to test the regulator "

____ With the use of an ohm-meter,, (then just-like as with a r/r.box with a fried-out rect/reg.circuit*), the meter's read-out should be near infinity regardless of set probe-polarity (between r/r.box-ground & either of it's two yellow-terminals), UNTIL the r/r.box's brown-terminal is fed with near 6-volts of positive-DC.
(* The stock (r/r.box)- units' internal-circuity is well-known to commonly be rather easily fried-out/burned-up if ran for very-long after the battery has become disconnected.)


Hopeful-Cheers,
-Bob

[JimF]

Hi Ted,

We'll wait for you to get back to the bike, but a blown headlight occurs because the either the glass envelope breaks or cracks and it looses vacuum on the inside (rare) or more commonly the filament wire breaks from vibration or over-voltage (and hence over-current.)


Regardless of the failure mode the end result is the same, the bulb goes from being a very low resistance in its working state to an infinite resistance in its broken state meaning it will draw no current (amps) whatsoever. So if you indeed blew out the headlight when you applied 12 volts it now wouldn't be able to pop a fuse unless you pulled the headlight out of the bucket and literally hammered the fuse with it.


In summation, your fuse is not blowing because of a dead headlight.



Jim

[ducwiz]

Hi Bob and others,


this is the circuit schematic of the 12Volt R-R for the 750GT L-twin. The 6Volt R-R circuit for the wide case singles is nearly identical; however, all resistors feature halved values. If this R-R is exposed to 12-14Volt, the circuit part grouped around TR1 will draw twice the current compared to the 6-7 Volt operation. This current may be excessive, so possibly burning TR1, R6 or the winding no.2 of the trigger pulse transformer T1 after some time.
Btw, TR2 together with mostly the rest of the parts form a flyback oscillator at ~30kHz, which fires the SCR gates.
During >25 years of working on those R-Rs, I often found dead ones, where the oscillator wasn't working any more, but the SCRs were alive and well. Unfortunately, the electronic circuit is potted in resin, so no repair work is possible

cheers Hans

[DewCatTea-Bob]

[quote="ducwiz"]Hi Bob
" The 6Volt R-R circuit for the wide case singles is nearly identical; however, all resistors feature halved values. If this R-R is exposed to 12-14Volt, the circuit part grouped around TR1 will draw twice the current compared to the 6-7 Volt operation. This current may be excessive, so possibly burning TR1, R6 or the winding no.2 of the trigger pulse transformer T1 after some time. "

____ Thanks for your contribution Hans, (it'd be nice if your postings were-not so rare as they've been) !
__ It wasn't really off-base for Ted to have suspected that perhaps he had caused his rect/reg.unit to go-bad, since it does have a terminal-lead that connects to the battery (through the ign.switch),, however I expect that you'd agree that the connection to his 12v.battery would-not have caused it's associated internal-circuit to go-bad & cause it to develop a 'short-circuit' (and-thus possibly cause his fuse-blowing issue).
__ Of-course I don't disagree with your post-wording which I've quoted, however I rather doubt that the connection to the 12v.battery would've burnt-open any internal-circuits during the rather non-extensive time it took him to complete his testing of his checked-out electrical-component circuits.



" During >25 years of working on those R-Rs, I often found dead ones, where the oscillator wasn't working any more, "

____ I never knew of exactly what internal-electronics become burned-out within those R/R.units, but they depend on a normally-working battery to hold-down the system-voltage,, so, whenever the engine is kept running at higher RPMs after the battery has suffered a broken wire-connection (or otherwise goes off-line), the R/R.unit's sensor-circuit is then exposed to excessive voltage (from the unregulated rectified alt.power),, and if done for a sufficient amount of time*, some component within that internal-circuit gets burned-out,, and AFTER that occurrance, the R/R.unit (once turned-off) thereafter is no-longer able to perform even it's relatively-simple rectification task, (let-alone regulate),, (just as in the normal-case whenever the key-switch isn't feeding the R/R.unit's sensor-terminal, except that the non-functional state remains permenant).
(* How long the unit's electronics can last without a connected battery, depends on eng.RPMs and whether the lights are left off or turned-on. _ So the varied conditions could kill the R/R.unit's sensor-circuit anywhere between 1/2 to several hours of operation.)
__ So if anyone ever notices that their headlight has started to 'flicker' and brighten-up (considerably more than normal) as revs are increased,
then suspect that the battery has gone off-line.
And if that's the actual case,, then ya have a chance of saving your stock w-c.type R/R.unit, by keeping system-voltage rather low (by running at reduced revs and/or keeping lights turned-on), until the broken battery-connection is restored-back to normal or the battery's std.function is otherwise brought-back to normal-operation.


Dukaddy-DUKEs,
-Bob

[DewCatTea-Bob]

By: TedsDucs ...
" will go back and try to trace the wiring to the fuses that are blowing. I have one on the positive lead from the battery that was blowing, "

____ That's not a stock location for a fuse but, it's a good-idea to have such a 'master-fuse' added (as CLOSE as possible to the battery's pos.terminal, wheneven such an inferior*method is chosen).
(* The most-superior method for adding a master-fuse is to locate it most-ANYwhere within the battery's NEGATIVE ground-wire circuit-connection !)
__ You failed to answer Jim's quite relevant question about the amp.rating(s) of your chosen fuses,, cuz if they are TOO low, then that could be reason for their blowing.
Your main-fuse ought to be rated for 25 to 30-amps.



" and also one inside the headlight. "

____ The stock fuse-arrangement has three fuses located within the headlamp... one fuse for the main-lighting (which ought to be rated for 15 to 20 amps), and one for the horn & brake-light circuit (which ought to be rated for 15 to 20 amps), and the 3rd.fuse for the parking-light circuit (which ought to be rated for 5 to 10 amps).
__ Since it's rather doubtful that you happen to have more than one short-circuit, it seems that you've made the mistake of having your main-fuse rated at the same value as the fuse that's blowing inside your headlamp. - (When identically rated fuses are both conducting the same circuit's current-flow,, even though both are 'rated' the same, one fuse will still inevitably be slightly less tolerant than the other and-thus will blow before the other gets hot enough to also melt all-the-way [which then possibly leaves the unblown fuse's rating reduced].) _ So in such case when ya replace either blown-fuse with the same rating-value, ya then can't be sure of which fuse-location will be the next-one to blow the circuit ! _ Thus you can then have your fuses blowing-out in either location, in the very-same mannor which you've experienced.
So for trouble-shooting purposes, your MAIN-fuse's amp.value MUST be rated at a GREATER value than any of the others !- (Opposite-wise, you'd then not be quided towards which-ever section of your system that's actually containing the short-circuit's actual location.)



" They both heat up and go when I turn on the ign key. No effect from the light switch. "

____ Okay then, it seems that a 'short' in the lighting-circuit is-not the cause then.
__ The ign.switch is supposed to directly-activate only the turn-on circuits for the R/R.unit and the ign.system...
And since the R/R.unit is likely not a source for a short-circuit, you should most suspect your ign.circuit. _ So next you should make-sure that your ign.points are held in their open-position before further checking for your short-circuit.
__ What wires do you have connected to each of your ign.coil's pair of terminal-posts ? _ The stock-system included a wire-circuit that connects the (B+)ign.circuit to a gen.warning-light within the headlamp, have you retained that stock circuit ?
There's also supposed to be a ground-wire running from the ign.coil-mount up-to the headlight... Do you have such a wire-circuit properly connected-up ?


Hopeful-Cheers,
-Bob

" My name is Ted - recent lurker and now looking for help. "

____ Welcome to our DUCATI-Single w.site Ted !



" the first battery I could find -
- and hooked it up to test electrics and see if I had a spark. What I only realized later was that it was a 12V battery I was introducing into a 6V system.... "

____ Connecting-up a 12-volt battery should only have one somewhat instant undesired effect (after the key-switch is turned-on), and that would be fairly short 6v.lightbulb-filiment life,, meaning that if the 12v.battery had been fully charged-up, the lights would've then burned-out within minutes after becoming powered-up.
However if the battery was low on stored power-juice, the 6v.lights's rather high current-draw would've then likely caused the battery's voltage-level to drop-down to perhaps under 10-volts,, which then would've made life a bit easier for the light-bulbs, (providing that your 12v.battery wasn't too large to be much affected by such a connected load).



" the lights did work - very bright, by the way!. "

____ Lights will indeed be overly bright whenever powered by excessive voltage/power, but they won't last very long that way... So either you didn't leave your lights turned-on for very-long, and/or your 12v.battery wasn't charged-up to it's normal storage-capacity.



" after the rebuild, and I hooked up the correct 6V battery, all I get is immediately blown fuses. "

____ That really OUGHT-to have nothing to do with having previously hooked-up any 12v.battery !
__ WHAT "fuses" are blowing ? _ And do you mean ALL/separately-installed fuses (in their separate fuse-locations), or merely-just multiple replcement-fuses in just one fuse-holder/location ?
Also, do you have all your fuses wired-up same as factory-stock ?



" I have traced everything I can. I did find a few chafed wires in the headlight bundles - what a rat's nest in there! - but can not seem to find a likely culprit for the short. "

____ Do your fuses blow whenever you simply connect-up the battery ? _ Or do they blow only after you turn-on the key-switch, or light-switch ?
__ IF only-just the fuse that's intended for just the main-lights blows only whenever the light-switch is turned-on, then I'd be most apt to suspect that one of the two power-circuits to the headlight-socket is out-of-place & finding a short-circuit to the HL.ground-circuit.
If so, then that likely wiring hook-up error should be checked-out.



" Did I fry the regulator and/or coil when I hooked up that 12V battery? "

____ The ign.coil should still be okay, even after many hours of running with 12-volts ! _ As it would then only become a bit warmer than normal when running at a higher than specified voltage.
__ The stock w-c.regulator is set-up to be non-functional without first being 'turned-on' by a 6v.battery with a minimal-charge. _ Your 12v.battery no-doubt fulfilled that requirement,, however I rather doubt that even if it had been FULLY charged-up (to 13.8v), could it have possibly compromised any of the regulator's internal circuity. _ (I'd expect it's related turn-on circuit to hold-up against at-least 24-volts before possibly surcoming to being overpowered.)
The rest of the stock w-c.type reg.box's internal-circuity is relatively independent of the battery, so I'm fairly sure that YOU haven't impaired it (with the 12v.battery connection).



" I did try to kick it a few time to look for a spark... "

____ And-so what did you see then ? _ (As there's no [stock] fuse for the ign.circuit.)



" Any good tricks to test the regulator "

____ With the use of an ohm-meter,, (then just-like as with a r/r.box with a fried-out rect/reg.circuit*), the meter's read-out should be near infinity regardless of set probe-polarity (between r/r.box-ground & either of it's two yellow-terminals), UNTIL the r/r.box's brown-terminal is fed with near 6-volts of positive-DC.
(* The stock (r/r.box)- units' internal-circuity is well-known to commonly be rather easily fried-out/burned-up if ran for very-long after the battery has become disconnected.)

NOTE - My Firefox-browser has lost it's feature to highlight & delete this above shaded-section ! _ I wonder if that's the same reason why Ted had also left it included within HIS postiing as well ?

[JimF]

I would propose to Ted that for diagnostic reasons that he disconnect the wires going from the rectifier/regulator from the battery, that he charge the battery to be sure it has a healthy amount of power contained within, and then without running the bike that he test the electrical system.


For the most part (ignition circuit excepted) Ted can affirm that the lighting circuits, horn, switches and wires are all functional or if there is a fuse blowing he can then pursue that problem. Like Bob says, just make sure the points are open so as not drain the battery through the coil or overheat the coil. If the points are closed a high amount of current will flow through the coil and drain the battery quickly. If Ted doesn't want to lay on the ground to look at the points or doesn't have a lift, turning the bike on and touching the ignition coil for a short while (less than a minute) will reveal if the points are closed by becoming hot to the touch. If the points are closed Ted could engage a drive gear and rotate the rear tire a few inches to open the points.


The astute people on this list will know that in the rare case of a shorted condenser in the ignition circuit, that particular ignition circuit problem will manifest itself during the diagnosis of the lights, horn, fuses and wiring but I would suggest that this rare fault would cause a fuse to blow and thus would be traced and identified during this first stage of electrical system testing.


This creates a watershed of functionality in the electrical circuit. I would think that only leaves the ignition circuit and the charging circuit as untested and unproven.


I believe the consensus is that a load (the battery in this instance) is required to be electrically on the R/R unit to prevent internal damage to its electronics when the engine is rotating so connecting that back up and trying to start the bike would begin to test the ignition circuit. Once again with a fully charged battery, If the bike starts or if combustion is audibly occurring the ignition circuit will have been verified. That's not to say the motorcycle is necessarily timed right, but at least the ignition circuit's functionality will be confirmed. If there is no combustion the spark plug can be pulled from the head, it's outer metal shell grounded to the motorcycle and its electrode examined for spark when the engine is kicked over. If there is no spark then the ignition circuit fault can be diagnosed and repaired.


Here again another watershed has been formed, that is both the lighting/horn/etc. and the ignition circuit have been verified as functional, and that leaves only the charging circuit as untested. If a fully charged battery runs down during initial shakedown runs, the alternator/regulator/rectifier and perhaps the battery itself should be considered suspect. What will be advantageous is knowing that the motorcycle's electrical system is functional save for creating DC voltage derived from engine power with which to run the bike and re-charge the battery.


Jim