z900 current drain

[gray]

Having a problem with my old zed. Basically standard but dyna coils and dyna S ignition. Dave Ennis redid the loom 1989 but it's done 60,000 miles since then
With a fully charged battery voltage across the battery = 12+V and holds a charge Ok, Turn the ignition on and the voltage drops to 7 and keeps plummeting. Goes back to 12 when ignition turned off or onto Park. Signs of overheated wiring in the connector block to the ignition switch ( and brown wire feels hot) and signs of heat in the blue wire and connection blocks in the clocks lamps sub-loom. Fuses all ok tho white wire feels warm
However , when raiding the spare parts cupboard and replacing the sub-loom and the ignition switch for another one , still does it.
With the dyna S red wire disconnected and ignition on , voltage stay 12+V
Does a dyna system draw a lot of power?
With engine running , voltage across the battery is 14+V
I've stripped the loom off and opened it all up- no sign of melted wires crossing each other
Any ideas fellas?
Gray

[ZedHead]

Have you tried another battery?

[gray]

No. This one was a new sealed/ maintenance free one last Spring

[Jay1969]

I heard somewhere that Dyna S does draw quite a bit of current, to overcome this, there is a modification you can try called the "wired george" mod, by adding a relay to the circuit from the battery, thus:

coil_diagram.jpg (23.72 KiB) Viewed 7091 times

https://www.wgcarbs.com/index.php/using ... s/89-coils

[Julian_Boolean]

If it's been fine and gone wrong without any changes being made then you have a fault rarther than the Dyna S drawing current as a normal function, if the voltage only drops with the Dyna S connected then the fault is with the Dyna S, inspect all the wiring carefully, most likely place for a fault is where the wiring goes through the casing.

Take a logical approach to fault finding and you'll be okay

Most likely cause of fault - something has been changed by someone, if nothing has changed then eliminate componenets one by one.

[gray]

The Dyna S is a recent addition last summer. I had changed the exhaust but hadn't re-routed the cabling from the points casing. So the new exhaust was closer and fried the dangling wiring from the Newtronic system I had on it. So I upgraded to Dyna , the bike misbehaved later that summer in Ireland ( flat battery , misfires etc) but I had attributed that to the constant torrential rain we had all week. In retrospect it might have been this same issue first surfacing.

[ZedHead]

No. This one was a new sealed/ maintenance free one last Spring

Still the main suspect In my humble opinion.

To drop from 12 to 7 volts you have to be drawing a massive amount of current or the battery must be duff. Even a conventional 12N14-3A battery should be capable of delivering circa 125 amps! It is extremely unlikely your Dyna S is drawing even close to this, particularly as it is not obliterating the main 20 amp fuse.

the bike misbehaved later that summer in Ireland ( flat battery , misfires etc)

Sounds like the original regulator and it has probably goosed the battery. Bin it, fit a combined unit and do the "Wired George" mod while you are on.

[KeithZ1R]

pull the RHS Switch apart and check something isnt amiss in there, the brown wire feeds the lights /ignition and horn from this location, mebe a red herring but worth a look !

[z1bman]

have you tried it with the kill switch in the off position

[ZedHead]

To clarify my understanding, the voltage is dropping at the battery terminals only when the Dyna S is powered up?

Unless the Dyna S has a massive short circuit this is probaby inconclusive. When powered up, apart from the the power that the Dyna S itself consumes, it will start to work. Assuming the pulse wires remain connected to the coils, the unit will instantly ground one or both of the coils depending on crank position. Effectively placing between 1.5 to 3 ohm load on the 12v feed to the coils or around 4 amps through each grounded coil, up to around 8 amps in total. This would normally not cause any problems for a good battery. To prove the point try disconnecting the black and green wires from the coils before connecting the red to the Dyna S. If the voltage stays at 12v the Dyna S is probably ok and your battery is sus.

[gray]

I took the battery out last night and put it on the optimate. This am the optimate says the battery is "weak" . I've already had the R switchgear apart and checked all the wiring. Never tried the killswitch on/off tho. Battery replacement seems inevitable now however. Where do I get one of these relays - do I just read then the mumbers as per the diagram?
Ta very so far

[ZedHead]

viewtopic.php?f=22&t=26357

[Gus]

http://www.halfords.com/workshop-tools/ ... inc--diode

http://www.halfords.com/workshop-tools/ ... -30a-4-pin

[KeithZ1R]

http://www.vehicle-wiring-products.eu/p ... with-diode

you will get everything you will need here including the japanese bullit crimp connecters

[gray]

OK new battery ordered , just checked the voltage regulator/ rectifier combined unit I have as per the youtube video on the club website and it's ok , moving the kill switch makes no difference.
Nothing obviously wrong when I look at the dyna ignition behind the points cover ( e.g. full of water/ melted bits etc)
I'll try the battery and see where we go , and keep you all updated.
Many thanks
Gray