voltage drop - blown 'lights' fuse

[Gorminrider]

There's so much information on this topic; ground-loops, high performance power, charging system quick test, stator papers, ...
I'm a bit at loss at where to start.

I have a '78 GS1000, with SH775 rr and regular light bulbs (no LEDs). SH775 + is connected to where the old RR was connected to the harness, the negative is connected directly to the battery.

The 'lights' fuse keeps blowing at irregular intervals. I haven't seen any other electrical issues.

Today I measured voltage between the main fuse and the lights fuse and notice a voltage drop of about 2V.
Engine off, I read about 12.8V at the main fuse (identical with battery voltage) and around 11V at the 'Lights' fuse (ignition & lights on)
Engine on (idling rpm), I read about 14V at the main fuse and around only some 12V at the 'lights' fuse.

The H4 connector at the headlight had also about 12V with the engine idling.

I checked all connectors - cleaned and sprayed them with WD40, all seemed plenty clean and solid. Fusebox isn't burned and solidly soldered.

I didn't find damaged cables or connectors.

Weird thing is that the fuse doesn't looked blown; it's visually still intact. Still the connection is broken, seemingly because the center thread disconnects from the ending tips. Batch of bad fuses?

I'm wondering what causes the voltage to drop so massively and what causes the fuse to blow.
Where to start looking further?

regards—

an alternate view, They are unrelated:

A SHORT is most likely causing the fuse to blow. Or just possibly, if your headlight is burning extremely bright for a second, you regulation has dropped out...

The Voltage drop is a different subject-ie you aren't bblowing fuses as you play with it? but it's pretty common on these bikes on the lighting circuit....However you might happen to fix the short by polishing your wiring up.

Get rid of the glass fuses for blade-type ,if you haven't already. It's too hard to find quality replacements it seems.
WD40 is a "water-displacer . I guess it's a coating too because I've heard technicians cry if they have to repair electronics yokels (their comment) have sprayed with it...

[crookedspoon]

an update and some measurements:
I implemented the Single-Point-Ground.
I took all connections apart, sprayed them thoroughly with contact cleaner.
I took the ignition out and cleaned that thoroughly because those contacts were diiiirty
I put in a LED headlight - wanted to do that anyway.

with the engine off, contact & headlights on, I measured:
At the battery: 12.35V
Starter relay (+) / RR - SPG (-): 12.27V
Main Fuse Hot (+) / RR - SPG (-): 12.08V
Main Fuse Dead (+) / RR - SPG (-): 11.77V
Lamps Fuse Hot (+) / RR - SPG (-): 10.99V
Lamps Fuse Dead (+) / RR - SPG (-): 10.30V


That seems like an awful lot of voltage drop between one side of a fuse and another side of a fuse.
And between Main Fuse Dead and Lamp Fuse Hot there's the biggest drop!

I tried to clean the contacts. What now? Flat fuses? Re-crimp all connections?

[Steve]

Go back and read post #8, but concentrate on the connectors and the ignition key.

Not sure if your bike has a connector right next to the fuse box, but that is one place to look.

You WILL have a 4-pin connector about 6-8 inches from the ignition switch. Check that connector, but also the actual contacts inside the ignition switch.

.

[posplayr]

an update and some measurements:
I implemented the Single-Point-Ground.
I took all connections apart, sprayed them thoroughly with contact cleaner.
I took the ignition out and cleaned that thoroughly because those contacts were diiiirty
I put in a LED headlight - wanted to do that anyway.

with the engine off, contact & headlights on, I measured:
At the battery: 12.35V
Starter relay (+) / RR - SPG (-): 12.27V
Main Fuse Hot (+) / RR - SPG (-): 12.08V
Main Fuse Dead (+) / RR - SPG (-): 11.77V
Lamps Fuse Hot (+) / RR - SPG (-): 10.99V
Lamps Fuse Dead (+) / RR - SPG (-): 10.30V


That seems like an awful lot of voltage drop between one side of a fuse and another side of a fuse.
And between Main Fuse Dead and Lamp Fuse Hot there's the biggest drop!

I tried to clean the contacts. What now? Flat fuses? Re-crimp all connections?

looks like you are demonstrating a dirty fuse box; I would do something about that.

[crookedspoon]

@steve:
there's no connector next to the fusebox. The 4-pin connector coming from the ignition is inside the headlight. Unplugged & cleaned it with anti-rust & contact spray. Took out the ignition itself as well and cleaned everything there (copper plates) — did all that before the voltage readings below.

@posplayr
here's pics of the fusebox. looks clean and solid enough — either way, the numbers prove me wrong. I guess I'll be installing an aftermarket box with flat fuses.

https://www.dropbox.com/s/c1bc95oifgr1tbx/IMG_4446.JPG

https://www.dropbox.com/s/hjh6lmo55uzle3e/IMG_4447.JPG

[posplayr]

It is standard procedure to take the back cover off of the fuse box and chemically clean out those crimps. Then using flux heat each crimp and flow a small amount of solder to block further corrosion.

[crookedspoon]

There're no crimps -> cables are soldered directly to the contacts (see second pic)

IMG_4447.jpg

It is standard procedure to take the back cover off of the fuse box and chemically clean out those crimps. Then using flux heat each crimp and flow a small amount of solder to block further corrosion.

[posplayr]

There're no crimps -> cables are soldered directly to the contacts (see second pic)

[ATTACH=CONFIG]50390[/ATTACH]

It is very common for the GS1000 fur boxes to get hot. The fuses literally will melt together. This is the first time I have actually see the inside of one, but most of the SSPB I sold were to GS1000 owners.

That fuse box looks filthy; it could be worse but there is little suprise if it would have high resistance between those plates secured with the pressed rivets. You need to chemically strip the oxidation between the plates, and shoot it with some contact cleaner(no WD40!), then try and flow some solder into the seam (using flux) between the clip and the bar that the wire is soldered to.

Simply follow the physical flow of where the current has to go to get through the fuse box. If there is anything that is press fit, it has probably corroded over the years and that is the problem.

[crookedspoon]

replaced the fusebox with an aftermarket one (flat fuses).
Voltage loss went from 2V (battery to light fuse dead side) to 1V.
Definitely better, still some searching to do.

thanks for all the feedback so far!

How much of a voltage drop could be considered 'normal'?

side question: what's the recommended way to join 4 wires together? wire nut with tape to keep it in place?

[Gorminrider]

side question: what's the recommended way to join 4 wires together? wire nut with tape to keep it in place?

"Recommended"? the answer is no wirenuts. Crimps only. Some like to work some solder in too. i don't. It's another metal added= corrosion. Plus it needs doing at the proper heat without corrosive flux (rosin core only) on clean clean wire. But you decide. I am leery because it fails around salt.
IMO, If you look at what Suzuki did, and duplicate it, you can't be far wrong.
But there are funkier ways that can last a long time. Wire nuts would be way down that list.
Add_It's not that I have never used "wirenuts" but in the end, if for no other reason, consider the ugliness of trying to seal them such that they don't come apart or corrode...it gets to be pretty ugly and they don't tuck away very well.

How much of a voltage drop could be considered 'normal'?

If you change that to "SHOULD be considered normal it'd be "none to 0.5 volts." but that's ideal. "could be considered normal" is whatever you can't fix but doesn't seem to hurt anything long term. If you consider the wiring diagram you will see that some electrical paths are longer and go through more switches and contacts than others and these, with higher currents flowing through, will have more vd. (Ignition,head light)