Regulator rectifier woes. Help!

[Hamel]

My Ducati 900SS has a SH548-12 Regulator/Rectifier off a Kawasaki (the legacy of an auto electrician having changed a whole lotta things when he revised the wiring loom for my projector beam headlights etc.

Right now its only putting out 12.3 Volts (just enough to get me somewhere with a flat battery )

I've already asked for recommendations for a good sparky in Christchurch but my question is this: "Might the R/R not be powerful enough for the bike?" They used this type on old GPz750s KLX650s etc

I really have no idea about such things, but replacing it with another SH548-12 (the first one fried itself) is beginning to seem like a bad idea...

Is anyone familiar with the reasons the R/R might be delivering a low charge?

[vifferman]

You need to test the battery, alternator and R/R together to work out where the fault is, but more often than not it's the R/R at fault (the components inside get fried). However, whehn this occurs it often buggers up the battery as well, but only if it's supplying unrectified current or excess voltage. Most R/R's fail the other way (perhaps by design?) and don't let enough ergs through, as it sounds like has happened in your case.

There's no problem with buying another R/R the same - it sounds like the one you had was already secondhand? However, you're better off buying a new one. The one you have is a Shindengen, as many R/Rs are, especially those supplied to Honda and Ducati. The later ones are better though, as they are more robust, have finned heatsinks (heat kills the R/Rs eventually) and many of them have a 'monitor' wire that allows the R/R to control the current delivered more accurately. The only problem is they may have different plugs (assuming yours is plugged in) which is only a minor problem as hard-wiring the R/R is better anyway. The plug is a source of potential failure, either via a partly broken or loosely connected wire or corrosion on the terminals, either of which can cause the connections to overheat and die.

[jim.cox]

I have a spare regulator that might fit.

You are more than welcome to try it.

Drop me a PM if you are want it

[CookMySock]

"Might the R/R not be powerful enough for the bike?"

R/R don't work that way. R/R are a shunt device. That is, when the battery voltage is too high they short the alternator out so it stops charging. If you watch it in operation with a multimeter, you will not see this happening because in practice it flicks on and off quite quickly, and the multimeter averages the readings out.

The bottom line is, you need to test the parts of your charging system seperately and isolate the faulty part.

The stator - can develop a short to the engine or open circuit, check with ohmmeter.

R/R - can go faulty, test with ohmmeter and chart.

Battery - can sulphate up or loose a cell, charge overnight and then measure terminal volts, or load-test it.

You might charge the battery overnight and see what volts it reads then. If its still low, you might just be up for a new battery.


Steve

[p.dath]

I know nothing about this ... if you shorted the alternator out wouldn't it act like a brake on the engine?

I know if you short an electric motor out that is driving something (like a flywheel) it has a breaking effect.

[CookMySock]

I know nothing about this ... if you shorted the alternator out wouldn't it act like a brake on the engine?

Yes, which is why they are removed or disconnected for racing. Try unplugging the stator from your regulator with the engine idling - you can hear the revs change. Don't touch the plug, hehe.

Because the windings have quite a large resistance, and because they are oil-immersed, you can just short them and force them to dissipate all the generated voltage as heat in the windings. It doesn't sound right that they can be shorted and theres voltage but theres no voltage.. /me mumbles something about kirchoffs equivalent circuits.

Steve

[vifferman]

In case you want to diagnose the faults yourself (or someone else wiht a similar problem reads this thread), here's a handy link.

[Hamel]

Thanks for the tips guys. Just FYI, the battery is new and I've had it on a battery tender (trickle charger) over the winter.

I'm going to take the bike to an Auto electrician in a couple of days so he can check the whole system. (Might come back to you re your kind offer Jim, thank you)

I bought the R/R new (at least Norjos said it was new, I suspect otherwise) about 500Km ago. Not a lot of k's to fry the R/R.

[vifferman]

I bought the R/R new (at least Norjos said it was new, I suspect otherwise) about 500Km ago. Not a lot of k's to fry the R/R.

Indeed not. You should've got upwards of 5 years out of it, rather than 500km.
But it may have just been one of the underspec'd ones, and they fitted it because it was plug'n'play.... er... perhaps "plug'n'pray" in this case.

[CookMySock]

I bought the R/R new (at least Norjos said it was new, I suspect otherwise) about 500Km ago. Not a lot of k's to fry the R/R.

Sounds like theres a stator fault to ground. That will destroy a R/R.

Do you have an multimeter?

With the engine stopped, measure ohms from each stator wire to the engine frame. They should all be infinite ohms - open circuit.

With the engine idling, measure AC VOLTS from the bike frame to each stator wire in turn - should be ZERO volts each.

With the engine idling, measure AC VOLTS from each stator wire to the other - should be exactly the same voltage between any and all combinations (20V AC approx - rising to 60V AC if you give it a good rev. Don't touch the terminals - it won't hurt you but you will probably drop your meter hehe.


Steve

[ralley]

Check the wiring and connectors from stator to battery thoroughly. Early 90's Duc's are famous for having weak wiring and connectors. Especially the two bullet connectors in the yellow wires from the stator to the reg/rec are well under spec and exposed to the environment. Over time they corrode and cause high resistance, the additional resistance increases the current and subsequently the heat, melting the insulation off the stator wires. When this happens they short together or to the frame and take out the reg/rec.

Pull the connectors apart and clean with some contact cleaner and check the wiring for signs of burning/melting. A good mod is to replace the wires between the stator and reg/rec with a larger gauge and replace the connectors with a permanent soldered connection well sealed with heat shrink. Some guys also like to re route the wires so they are not touching over their whole lengths.

Also check your reg/rec is not covered in crud thrown up from the front wheel, this can cake them and prevent them cooling nicely.

The early bikes had under spec'd alternators that were gradually upgraded over the years (went from 350w to 500w). I suspect an orphan year SS like yours probably even more so, trying to run the projector beams may be too higher load.

In general as the reg/rec just shunts the load (producing more heat, which they hate) pulling more current is better (less to shunt, less heat). So keeping your lights on is actually easier on the system.

Rob.

[Hamel]

The early bikes had under spec'd alternators that were gradually upgraded over the years (went from 350w to 500w). I suspect an orphan year SS like yours probably even more so, trying to run the projector beams may be too higher load.

Rob.

Spot on Rob. The alternator has crapped out. I guess the best solution is to get a stator from a later model bike? Is there anyone around who would rewind my Stator? Is the increased wattage merely a function of better (gauge?) wire or should I just try to find a new (later model) Stator?

Will pull the motor apart and check it anyway. >Sigh<

Great advice by the way. Thanks!

[Kickaha]

Is there anyone around who would rewind my Stator?

This guy does them and has repaired a few for members on here, he turned mine around ex Chch within a week
J.Halsey Rewinds
Auckland
0-9-534 4161

And this guy off trademe does them to
http://www.trademe.co.nz/Members/Lis...?member=302802

[CookMySock]

They are a bit of dicking around, but you can rewind it yourself. They have to be dipped in shellac and baked afterwards.

The headlights won't affect the stator load at all. It will more likely be caused by a winding touching the core and shorting out. It seems a pretty common thing to happen to bike stators.

Steve

[Hamel]

Before I pulled the engine apart I was going to check the wiring (per Rob (ralley)'s advice, below. So following Robs lead (cough cough) I jumped on www.ducati.ms, the most helpful Ducati forum I've found to see if anyone else had has similar issues.

The below advice is from Larry Kelly (aka Shazaam) of San Diego CA. Larry wrote an outstanding article on Ducati Charging issues which you can find at http://www.ducati-upnorth.com/tech/chargingfailure.php

I contacted Larry last night and he said:

"Yes, it's unlikely that the stator windings need replacement, just the lead wires. Do this first. Once replaced there's really no need to use a higher wattage system. Read this and get back to me if you have questions.
Here’s the basic problem.

The loops of wire that comprise the stator itself are coated with an insulation coating that prevents the wire loops from shorting together. So failure of the stator itself almost never occurs. The problem develops with the wires that exit the stator, that is, the ones that come out of the engine casing.

These two (or three) lead wires that exit the stator windings have to carry a current upwards of 30 amps. The voltage differential between these lead wires increases with engine speed to around 70 VAC.

If the insulation on these lead wires can’t hold back this voltage they’ll short together somewhere along their length where they physically touch, or short to a grounded component, at some intermediate voltage/engine rpm. If you short out these wires, your voltage regulator/rectifier that they connect to will be damaged and need replacement.

Adding to this problem is that the lead wires are partially routed in close physical contact with each other within a common sheath. This sheath is intended to provide supplementary insulation to prevent shorting between the wires and adjacent grounded components. Unfortunately, when the insulation gets damaged the lead wires will short - inside this sheath - where they are forced to touch.

So, the insulation gets damaged by heat and looses it’s ability to prevent shorting to adjacent components. It gets hot inside a fairing (and this doesn’t help) but engine heat not the main cause of insulation damage.

Ducati could have used a larger gauge wire and a better heat resistant insulation, but again, this is not the primary reason for RR failures.

The damage occurs because the in-line connector that allows the regulator/rectifier to be detached/replaced develops a higher and higher resistance as it develops corrosion and/or loosens under normal usage. This causes I-squared-R heating at the connector, and because copper wire is an excellent conductor of heat, ALL the adjacent wiring gets hot, really hot. For example, a small one-half ohm increase in resistance at the connector causes a typical 30 amp current to develop 450 watts of heat.

The mistake most owners and shop workers make is to cut-out and replace only the crispy portion of the wiring. Not good enough.

Here’s the basic solution.

You have to replace all of the wiring that was heat damaged and take steps to assure it won’t happen again. Otherwise you’re going to be replacing your regulator again, and soon.

As luck would have it, the stator lead wires do not touch each other inside the engine casing, so even when the insulation is damaged they can’t short together. So there’s no NEED to replace the wiring inside the casing.

So my advice to ALL Ducati owners is to make this a winter project. Replace all the wiring between the engine casing and the regulator leads with PVC-insulated AWG 12 gauge from Radio Shack. Larger 10 gauge is even better, less resistance per foot. Then solder the wires together to eliminate the heating source. Remove the common sheath to physically separate the wires and use stand-off insulators where the wires come close to grounded components."

Will try this next. Good call Rob and thanks to all!