Slight voltage leak through starter solenoid

[Doctor Shifty]

I've been having a nuisance problem on my 81 GS1000G with the battery slowly draining over several days if I don't ride. Seeing as how the battery was recently replaced I am now checking its state more often, and have found this problem.

With ignition off there is a very slight drain. I took the +ve wire off the battery, connected a multimeter between the +ve terminal and the wire. There is a 0.01 volt drop across what should be a zero volt link.

The wire goes to the solenoid and the fuse block. It's either the solenoid or elsewhere in the system that it's losing it. I checked the fuse block link as most likely but no voltage drop there. The bike's wiring is OK.

I connected the solenoid by itself. It shows the 0.01 volts. Looks like the solenoid terminal is not isolated like is should be. I suspected the built up of gunk letting a few electrons pass.

Pulled the solenoid apart. The terminal bolt holds a copper plate inside. There's nothing else. It is just sitting in the plastic housing waiting for the armature to connect it to its mate across the other side. So this bolt/plate piece is sitting on an insulated plastic housing and losing voltage. :?

I cleaned the insides with solvent. Put it all back together. Put in in the bike. the same thing happens.

This leak is very small, but it's enough to discharge a new Yuasa battery in a couple of days.

Why does an insulating plastic housing decide to not insulate?

[Steve]

Is the solenoid the ONLY thing on that wire?

I ask because I only have one wire attached to the positive terminal on the battery. Anything that is connected to "constant" power (digital voltmeter) gets its power from the battery wire on the solenoid. Make sure there are no other wires connected to the solenoid (on the battery wire terminal), then measure again.

Generally speaking, there is no reason there should be any "leakage" inside the solenoid unless it's really dirty inside, and you said that you cleaned it out.

Measuring voltage is an easy measurement, but the one that really matters would be current. Move your meter selector to DC Amps (or milliamps) and let us know what that reading is.


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[jfrankenbiker]

I wouldn't use the amps setting on your multimeter for this. It will smoke your multimeter or blow its internal fuse if the current leak exeeds the limit of the multimeter (which is very low).

Better to follow the red wire from the +ve battery terminal up to the ignition switch to see if you can find a possible source for the leak (Look for a spot where the wire coating has pinched or rubbed through) like under the tank or in the headlight bucket.

Ignition switch itself may also be leaking (highly suspect). Test across it with your ohm meter when the switch is off.

Another possibiliy is that the diodes in your voltage rectifier are leaking current backward.

[chef1366]

I agree. Clean the ignition switch.

[hp1000s]

I'm goin' with bad diode in rectifier...put VOM between negative cable & battery - terminal; then disconnect one item/appliance at a time till voltage stops. BINGO!

[Steve]

I took the +ve wire off the battery, connected a multimeter between the +ve terminal and the wire. There is a 0.01 volt drop across what should be a zero volt link.

I wouldn't use the amps setting on your multimeter for this. It will smoke your multimeter or blow its internal fuse if the current leak exeeds the limit of the multimeter (which is very low).

Most multimeters have a current limit of about 10 amps. He indicated that he measured 10 millivolts from the battery to the starter solenoid lead. I'm not going to say it's impossible, but there is nothing on these bikes that is going to flow 10 amps of current with only 10 millivolts pushing it.


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[Doctor Shifty]

Is the solenoid the ONLY thing on that wire?

I ask because I only have one wire attached to the positive terminal on the battery. Anything that is connected to "constant" power (digital voltmeter) gets its power from the battery wire on the solenoid. Make sure there are no other wires connected to the solenoid (on the battery wire terminal), then measure again.

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From my original post :-
The wire goes to the solenoid and the fuse block. It's either the solenoid or elsewhere in the system that it's losing it. I checked the fuse block link as most likely but no voltage drop there. The bike's wiring is OK.


The wire comes from the battery to the solenoid. At the solenoid end it sends another wire to the general bike wiring. Three inches along that wire is a connector. I undo the connector and the solenoid is the only thing in the loop. Lift the wire away from the solenoid bolt and the 0.01 volts drops to zero. Connect it straight to the bike's wiring and it's also zero.

[Doctor Shifty]

Thanks for the replies, guys. But...

The ignition switch is not in the loop.
The rectifier is not in the loop.

Both of these are part of the general wiring, and there is no problem when I connect the battery to that without the solenoid connected.

At the moment I am leaning towards the rubber gasket that sits between the bakelite holding the connectors and the metal case of the solenoid itself. It might be touching the bottom of the live contact plate in there. There was a fair bit of copper dust from 25 years of use that I cleaned out, perhaps the rubber is a bit ingrained.

Looks like it's going to have to come off the bike again.

[mf70]

Are you one of the lucky ones that can get a replacement starter solenoid from lawn tractor parts?

If so, maybe it isn't worth opening it up again.