'80 GS850GT sudden electrical meltdown, hot igition coil

[SleepNSnooze]

Hello all, I am new to this forum. I would liked to have been able to contribute a bit of knowledge myself before posting, but I have ran in to a problem that I can't find answers for anywhere else.

I have a 1980 GS850GT. I had it running pristine, new plugs, oil, cleaned carbs, etc... But I needed to remount some front lights as I had taken off an old Vetter fairing that came with the bike. Whoever installed it used splice connecters to attach the fairing plug to the harness, so all of the original female connectors were there. I plugged in the OEM signals from the rear end up front to test and they were working fine, but when I plugged in the headlamp that I pulled from the fairing, things went downhill fast.

First a 10A fuse blew, which I replaced with a 15A as per the manual. This worked for a few minutes, but then it blew again. When it did, suddenly the ignition switch ceased to turn off any running lights, including the speedo/tach/indicator lamps. I had to unplug them from the harness to turn them off. Then a second fuse, the third one down, blew, and after that happened, the left-hand ignition coil become too hot to touch. I begun to smell burning and with the ignition switch not killing any circuits, I had to disconnect the battery.

Does anyone have any idea of what may have happened? I'm certain I made a bad connection when plugging in the headlamp, maybe a positive lead to something brushed up against a ground, but the fuses blew as they should when that happened the first time. The worst case scenario I can imagine is that a bad connection was made for long enough for some wires to become melted together, which would explain the ignition switch not killing anything when in the off position. That's something I don't mind sitting down and fixing, but what concerns me is why the ignition coil became as hot as it did. I didn't try to run the starter during all of this, but does power run through the coils regardless? I'm stumped, and a little worried that I'm going to have to drop some money on a new coil. Everything relating to the electrical appears to be stock, so unfortunately I can't blame any of my troubles on bad parts.

Any advice is much appreciated. I may be in a little over my head here because I don't have any electrical working equipment besides a 99-cent voltmeter, so I can't do resistance checks or anything like that.

 

[Steve]

Yes, when the ignition key is in the ON position, power runs through both coils. When the pickup on the right end of the crank spins around to the right spot, it tells the ignitor to momentarily open, which stops the current. When the current stops, the magnetic field in the coil collapses, which is what creates the spark. Note that the "ignitor" that was mentioned is just a box of transistors that are an electronic version of points that open up to stop the current flow. There is nothing magic in that box, it does not create any power, ironically, it does not "ignite" anything, yet is still called an ignitor.

Back to your problem: at the front of the bike is a four-pin connector. It might be just under the front of the tank, it might be in the headlight bucket. Wherever it is, you will find red, orange, brown and gray wires in it. The red wire comes straight from the MAIN fuse and feeds the ignition switch. The orange wire goes back to the fuse box to feed the three top fuses, LIGHTS, SIGNALS and IGNITION. It appears that something might have bridged across the red and orange wires, which would have prevented the key from doing its job.

Which fuse was the first to blow? I know you said a 10A, but what position was it in? There should only be one 15A fuse, in the MAIN position, which is fourth one from the top.

I can only guess as to the source of your 99-cent meter, but you will eventually want to invest in at least a 9.99 meter. While you are at it, invest in a test light. In cases like this, it is MUCH quicier and easier to use. You don't necessarily need to see whether you have 12.3 volts or 11.5 volts, all you need to see is if you have power on a wire where you shouldn't (or the other way around). Much easier to see if the light is on, rather than reading a display. While the "high-tech" of an LED is nice in some areas, I prefer a test light with a regular incandescent bulb. The brightness of the bulb is a bit of an indicator for how much voltage is there. No, can't tell 11.5 from 12.3, but you can certainly see the difference if there is only about 6 volts there.

.

 

[Redman]

First, Welcome to GSR.

Having power on things with ignition swtich off,,,, yikes,,,,, I can t see how anything you did with plugging in headlight had any effect on that. That problem would be in the ignitions swtich (crud bridging two contacts), or the wirng harness (wire insulation broke down and wire contuctors making contact) to the ignition switch.. or maybe inside the fuse block (main circuit bridged over to ignition-head-signal circuit).



Ew, probably going to have to troubleshoot that with a meter, disconnect connectors at ignition swtich and at fuse blck, measuing continuity beteween circuits and find what circuits are conected to each other that should not be...... will reguire good understanding of things and good use of meter. ... all which you say are not comfortable with.... humn....



Maybe get under the igntion swtich and pull the connector there and see if still have power to everything, if do, then know its not the ignition swtich powering things when it should not.

Maybe look at wiring harnes where it wraps around steering neck. look for some damage.

Pull tank, look to see if can see wiring harness damaged anywhere....

But is hard to tgroubleshoot eletrical problem, especaiuly this one, with your eyeballs.

Oh, about the ignition circuit, the kill swtich should kill power to the coils, maybe that might help in being able to keep power on everything else while trying to find the main problem.

.

 

[posplayr]

Rule #1 when a fuse blow DON'T get a bigger one

 

[Redman]

Ew... something else.
Look for the ground wire (blk/wht) that comes out of the wioring harness and grounded to bike frame under seat up top behind the battery box. Does it have the insulation melted off.....?
I will save you the horror story of what else can happen if that has happened.

.