Blows main fuse when I turn on the key?

[Guest]

Electrical problem. I have a 1980 GS750L. It’s been a great motorcycle which I bought from a member of this wonderful sight about 13 years ago. It had 9,000 miles on it when I purchased it, it now has 28,000 and change. Until a little while ago it has been a “turn the key and go” type of ride! Except for maintenance items, this little bike has been a delight to own and ride with NO issues. However, about two months ago I was running some errands around town and it just quit running. I found the main fuse blown. Didn’t think much of it, put a new fuse in (15 amp) and continued on with no problems. However, a couple weeks ago it did the same thing, but when I put in a new main fuse, the moment I turned on the key, it blew again. I got a friend to come get me w/ his trailer and the bike has been parked since. I bought some new fuses and tried it again today, and again the minute I turn the key on the main fuse just fries. So, I figured I had a short someplace in my wiring. I pulled the tank off and exposed all the wires, looking very carefully for a break in the insulation or an obvious spot in the wiring where a short might be. I found nothing. As a matter fact, all of the insulation on the wires looked great and I found no places that were compromised. So, anybody got a suggestion of what might be causing this? What should I look at next? Thanks.

[Gumpster]

PAC, I will get a wire diagram and revert back with suggestions. You can put a test light in place of the fuse and remove things from the circuit until the light goes out. Could be anything from a shorted handlebar switch or headlight or even a shorted coil. Be glad to help and electrical is my specialty. The good news is that I am local, was on the island today and live just south of Brunswick near exit 29.

[posplayr]

Unplug the R/R and see if the fuse blowing still happens. If not replace the R/R. Preferably series R/R (e.g. SH-775)

[Gumpster]

PAC315, looked at a diagram and have an idea. Remove the other 3 fuses and replace the Main fuse. It shouldn't blow when you switch on the key. The ignition switch powers the other 3 fuses so as you install the other fuses one by one, the circuit that causes the main fuse to blow will identify the culprit. If by chance the main fuse blows with the other 3 fuses removed, then the problem is the orange wire between the ignition switch and the fuse box. Hope this helps. PM me if you need some help.

[Gumpster]

Posplayr, I think the R/R is on this fuse but before the ignition switch so it would blow the fuse even with the ignition in the off position. He stated it blows when the ignition is switched to the run position.

[Redman]

,,,,,,,,,,,,,,,,,,,,, the minute I turn the key on the main fuse just fries. So, I figured I had a short someplace in my wiring. .......................

If the main fuse blows as soon as plug in a new one; then I would suspect the R/R.

But you say the main fuse blows as soon as turn on the key.
I say to remove the head, the Signal, the Ignition fuse and the Aux fuse. Then if main fuse blows when turn on the key I would suspect something along the Orange wire from the Ignition swtich to the fuse block.
If the fuse doesnt blow, then plug the other fuses one at a time.
I suspect it will be the Signal fuse (org/grn circuit), and if so, disconnect the org/grn wires from the horns and try it again. THe power from the Signal fuse (org/grn) goes straight to the horns and then the other wire gowes to the horn button to complete the ground. But if is problem in the horn it can then short the power to ground. You would think should blow the Signal fuse but maybe it gets the main. Oh, the signal fuse should be a 10.

[Gumpster]

Attached portion of wire diagram, note R/R item 5 not part of ignition circuit but powered even with ignition in off position.
image.jpg

[Tom R]

Check your horn.

[tom203]

Posplayr, I think the R/R is on this fuse but before the ignition switch so it would blow the fuse even with the ignition in the off position. He stated it blows when the ignition is switched to the run position.

You would think so , but if the r/r had an random internal leak,say 3 amps, then when ignition is on and/or starter button is pushed you'd could be exceeding the the 15 amp fuse

[posplayr]

You would think so , but if the r/r had an random internal leak say 3 amps, then when ignition is on and/or starter button is pushed you'd could be exceeding the the 15 amp fuse

Excellent deduction ,+10.

It could well be more like +5 amps but the same failure mechanism.

Very good. This is probably the best diagnosis I have seen here other than the fellow that figured out the leg to ground stator tests( it was not me).

[Gumpster]

A constant 3 or 5 amp draw with the ignition off. Really? That is a little more than an acceptable parasitic drain. Bike is fixed and it wasn't the R/R or stator.

[Gumpster]

5 amps is the equivalent of a headlamp on all the time even when switched to the off position. 60 watts.....

[Big T]

A constant 3 or 5 amp draw with the ignition off. Really? That is a little more than an acceptable parasitic drain. Bike is fixed and it wasn't the R/R or stator.

So, what was it?

[posplayr]

So, what was it?

Gonna take more than that; 29 questions?

[Rich82GS750TZ]

Has Elvis left the building?