Help on where to put the main 30 amp fuse


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mattiaGL
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Location: 6944 Cureglia, Switzerland
Motorcycle: HONDA GL1000 ED (Europeand Direct Sales), 1977

Help on where to put the main 30 amp fuse

Post by mattiaGL »



HI, to all here

I have a question for an expert: I replaced the main fuse that had been changed by the previous owner but I have a doubt: should the fuse be inserted
a) in line with the cable (red and white) that connects to the rectifier
b) in line with the cable (red) that connects to the main switch
c) the two solutions are interchangeable

I also have a doubt because if I look at the wiring diagram (see pic below), solution B (in line with red cable) seems to be the right one . On the other hand, if I look at the picture of the original spare part (see pic below) I see that the fuse line is that of the shielded cable with heat shield sheath, however between the two cables coming from the wiring harness, the shielded one with heat shield sheath and the one coming from the rectifier (red and white)

Furthermore, I would like to know if, in the case of a rectifier/regulator upgrade, it is recommended to put the fuse between the R/R and the Battery (actually it would be the starter solenoid connected to the battery...), actually solution A.

Thanks for your help

Mattia
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DenverWinger
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Re: Help on where to put the main 30 amp fuse

Post by DenverWinger »

I'd wire so that both the main switch and the rectifier are behind the fuse.

Thus the fuse protects from a short in the main wiring, and also protects from a shorted diode in the rectifier.
A local inventor has figured a way to turn a sausage grinder backward to manufacture pigs. :lol:

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Re: Help on where to put the main 30 amp fuse

Post by Rambozo »

I agree with Mark, but I'd go a step further and use two fuses, one on each wire. That way if you lose the charging from a shorted diode, etc. You can still limp home on the battery.
mattiaGL
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Location: 6944 Cureglia, Switzerland
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Re: Help on where to put the main 30 amp fuse

Post by mattiaGL »

OK thank you very much,
I think I will adopt this second solution of two separate fuses.
A suggestion for the fuse size of the charging circuit?
30 amps seems a lot for the R/R connection.
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DenverWinger
Posts: 2441
Joined: Thu Jun 23, 2011 2:20 pm
Location: Denver, CO
Motorcycle: (s)
'80 GL1100 STD Vetter (2005-)
'93 GL1500 Aspencade (2017-)
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Past rides
'72 CL350 (1980-1988) sold
'78 Suzuki GS550 (1985-2005) sold
'77 GL1000 (2002-2006) sold

Re: Help on where to put the main 30 amp fuse

Post by DenverWinger »

If you use the second solution I'd use a 40 amp fuse for the R/R.

In the single fuse solution, current draw from the main switch can be on the order of 20 amps, the R/R can supply that directly, and the surge of charge current to the battery when the engine is first started (up to 10 more amps) goes thru the fuse to the battery.

Maximum output of the R/R is pretty nearly 30 amps. In the second solution, there will be the 20 amps to power the bike from the R/R which will have to go thru BOTH fuses, and the additional 10 amps or so the battery might want for a short time after the heavy draw from the starter also has to flow thru the R/R fuse. Chance of blowing 30 amp R/R fuse simply because it is undersize.

40 Amp on the R/R will do the job, if there's a fault in the R/R the short circuit current will be much higher than 40 amps and the fuse will blow.


A local inventor has figured a way to turn a sausage grinder backward to manufacture pigs. :lol:

♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:
~Mark
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