Battery drain from solenoid? aka What is this wire?

[Danny Crawdad]

On my 81 Special, I have been having battery/charging problems. It runs great when it's running, but battery drops voltage after sitting and won't start the bike (sitting at around 12.25vdc it will turn the bike over a few times and then starts getting slooow cranking, and eventually drops below the threshold to crank).

Just to make sure it was actually charging, I went through all connections per the instructions of a bunch of threads here -- no corrosion, connectors and contacts all in good shape. Tested charging system, it is putting out about 14.60vdc at 2000-2500rpm, so I believe that to be healthy.

Today I disconnected the battery, and put my voltmeter in between the negative post and the negative cable, and saw a steady 0.30vdc draw. Pull main fuse, draw goes away.

Started unplugging connections and fuses, and found that what appears to be the 'source' of the draw is a single red wire that runs from the positive terminal of the starter solenoid near the fuse panel, to a connector, and then into the main wiring harness. I pull this connection, the draw drops to 0.00.

My question is this -- what is it, where does it go, and what can I do to find out what is causing the parasitic drop from this location?

I've attached a photo of what I'm talking about.

The wiring harness on this bike is factory and hasn't been cut into, so it is still wrapped tight from Yamaha, and I am really loathe to cut the harness wrap apart to trace it out.

Anyone have any insight?

Just to cover bases, I had the battery (new Interstate Cycletron II glass mat 360cca 18ah) tested, and although it was a little low to be fully tested at AutoZone, they said it was putting out 371cca, and appeared to be healthy. I hooked it to the battery tender jr to trickle to full overnight and I'm going to have them run the full test on it tomorrow, but I don't THINK (think being the key word) that this is the root problem.

Thank you for your help!
(note, the black on the shielding is not from a burn or anything, it is from spraypaint someone used to touch up the frame)

Sorry for the quality of the photos. It was dark and I am blind and any other excuse that I can come up with . The yellow sheathed wire goes to positive batt connection on solenoid, the red sheathed part goes into the wiring harness.

I looked at the wiring diagrams but I couldn't figure out what the hell this wire does. I have a feeling it's ignition?


100_3751 by crunchbones, on Flickr


100_3754 by crunchbones, on Flickr


100_3745 by crunchbones, on Flickr

[bikerphil]

IIRC, that wire you show goes directly to the main fuse. That glass type fuse box you still have is a known weak point, most of us replace with a Topcat blade type and our electrical gremlins disappear.

[crazy steve]

That's the main power supply wire for the bike harness... so in effect, it goes everywhere.

From this connection, it goes into the harness then quickly exits and goes to the 'main' fuse, which you'll find under the other sidecover; it will be that rubber lump just in front of the battery near the top. After going through the fuse, next stop is the ignition switch. If you unplug the ignition switch and the draw is still there, then this wire has a low-grade ground someplace, and you'll have to start looking at the main harness for damage.

If the draw does go away, plug it back together and pull all the fuses. The other three wires from the switch goes to the fusebox, so if pulling the fuses doesn't clear it, then the problem is in either the switch or the wires from the switch. The switches can get corroded inside, so that may be the problem. The switch can be disassembled and cleaned (there's a how-to here somewhere, do a search). Otherwise, check each wire to ground; if you get anything other than an open circuit on any of them, that's the problem wire...

I'm assuming you've already pulled the individual fuses without clearing the draw, so that's where the problem should be...

[Danny Crawdad]

Ha, that would explain why disconnecting it killed all power to the bike same as the main fuse behind the left side cover would . I basically discovered nothing, then! I'll follow the rest of the tests and see what's up. This may be a dumb question, but can I get to the ignition switch without removing the gas tank? I don't have the bike near me to check.

Phil, fusebox is my next step, I wanted to get this drain fixed, but if it takes replacing the fusebox to fix it, I'm game . I hate glass fuses so much. I'll contact the person selling them on here an go ahead and get one ordered, I know they are cheap.

[bikerphil]

Yep, Danny, remove the headlight and the ign switch connector is in the headlight bucket. If you do need to remove the ign switch, you can get it out with a 10MM 1/4" drive with swivel and extension.

[jetmechmarty]

Danny,

Don't be in a hurry to dismantle your wiring harness. Most likely, you have a bad component. Wiring won't short unless it's been tampered with. The exception being where the wires move, such as the steering neck.

Follow Steve's instruction. Divide and conquer!