On my 73 850 I've replaced the glass fuse with a Bussmann ATM blade fuse on the battery positive. I did this for the convenience of finding replacement fuses and I like to pull the fuse when the bike isn't going out for any length of time. Last night I was checking my battery voltage with a multimeter. The fuse was removed and I probed the black lead to battery negative and the red lead to the metal blade female receptacle in the fuse holder closest to the battery. The meter showed 12.8 volts. I then probed the the other metal receptacle expecting to see zero. The meter showed 12.73 volts there. Shouldn't this be reading zero? I have my 69 Triumph Bonneville set up identically and I checked that - 12.9 volts closest to the battery and zero on the other. Also, when I put the fuse into the holder on the Bonnie is slips in with no commotion. On the Norton when I put the fuse in I get a spark. I need to start tracing circuits, right?
Wiring/Fuse question...>
- Thread starter ommief
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ommief said:
Not necessarily, as the spark is probably the result of the 2MC emergency starting capacitor charging up (which takes about 1 second) so if the sparking only lasts for around a second or two (ignition switched OFF), that's perfectly normal.
If the battery has been disconnected, then a good 2MC will often take several hours to fully discharge, however, if the ignition is switched ON with the battery disconnected then the 2MC will fully discharge in about one second.
You could try disconnecting the 2MC (remove the red earth/ground wire) and see if that cures the spark/volt "problems"?
I don't know what effect this will have on your situation but I believe if you have a positive ground system the fuse needs to be on the negative(-) side of the battery, unless you are running a negative ground then it would be on the positive (+)ommief said:
Protecting your ground circuit is a moot point.
I see. So we have been putting it on the non ground side because simply that's what we are used to. I believe the correct term is standardization and for this reason it should not be deviate from.L.A.B. said:
Also, Isn't it proper to have the fuse at the start of the circuit to protect the wire at length.
pete.v said:
Whether it is deviated from or not isn't in question, nor would it be relevant.
Not all vehicles with positive earth electrical systems have the fuse on the battery negative side.
Examples:
Various Triumph, Norton, BSA:
pete.v said:
And with the fuse on the opposite side of the battery? What's the difference?
Also an electrical circuit doesn't have a "start" and a "finish" that's why it's called a circuit.
L.A.B. said:pete.v said:
In that case I think perhaps you should tell all the Commando (and other British bike) owners who've converted their bikes to negative earth/ground that it's not consistent?
Now look who causing trouble. You should be ashamed of yourself. We look up to, man
Lock it down!
I was going to casually suggest that it was OK to hang the fuse on the ground side if you like, since one of my bikes is wired up that way. The fuse pops just fine if you do something clumsy/stupid. In this case it made the fuse more accessible than if it was on the load side.
Glad I didn't bring it up tho, looks like Pete wants to go down fighting :mrgreen:
Glen
Glad I didn't bring it up tho, looks like Pete wants to go down fighting :mrgreen:
Glen
Likewise, makes no odds. One supply, one circuit ie. as on Commando, one fuse irrespective of where it is will provide protection in the Norton world.
If you have one or more DC supplies and multiple circuits then one fuse in Pos and one in Neg will give you protection of the circuit and will enable the others to carry on working as in the military maritime fit DC distribution systems. It works by the fact if a leg in another circuit goes to the structure it will not blow either fuse as there is no return path. If another circuit using the same supply has the opposite side go to hull there will now be a circuit via the hull and a fuse will blow, multiple earths and supplies can lead to big problems and a headache in fault finding. It also provides additional safety when a switch is incorporated into the circuit where the hull / frame is not used as the return. It is why DC earth checking on major systems is important, though our simple Commando is at the bottom end of this complexity we all know that it's a bugger sometimes finding those short circuits.
Simple and cheap solution, would be to use the hull as the return with one fuse, but then if one circuit went to earth then the return line via the hull would blow and all circuits would be isolated. Also the distance / resistance and the fact that the hulls potential difference is variable even over a few feet, would create problems in itself. I always thought that the hull was at 0V, but again this is not the case, a hull will have PD, and this is why you may see a common earth wire linking the outside of multiple electronic cabinets, and a common 0V line within.
The only convention I can think of is that the fuse needs to be as close to the supply as possible and and easily accessible. With cars, there are more circuits, therefore a bigger single fuse would be needed, it would work, but it is not the best solution as it would also dictate the size of all the downstream wiring as well, there is also the space to put a box with lots of circuit fuses within it which is the better option allowing smaller lighter cable to used.
This might be mumbo jumbo to many but the best advice is = Fit a fuse in either side and of the correct rating and all will be well, replace fuse = cheap, replace bike / garage = £lots.
If you have one or more DC supplies and multiple circuits then one fuse in Pos and one in Neg will give you protection of the circuit and will enable the others to carry on working as in the military maritime fit DC distribution systems. It works by the fact if a leg in another circuit goes to the structure it will not blow either fuse as there is no return path. If another circuit using the same supply has the opposite side go to hull there will now be a circuit via the hull and a fuse will blow, multiple earths and supplies can lead to big problems and a headache in fault finding. It also provides additional safety when a switch is incorporated into the circuit where the hull / frame is not used as the return. It is why DC earth checking on major systems is important, though our simple Commando is at the bottom end of this complexity we all know that it's a bugger sometimes finding those short circuits.
Simple and cheap solution, would be to use the hull as the return with one fuse, but then if one circuit went to earth then the return line via the hull would blow and all circuits would be isolated. Also the distance / resistance and the fact that the hulls potential difference is variable even over a few feet, would create problems in itself. I always thought that the hull was at 0V, but again this is not the case, a hull will have PD, and this is why you may see a common earth wire linking the outside of multiple electronic cabinets, and a common 0V line within.
The only convention I can think of is that the fuse needs to be as close to the supply as possible and and easily accessible. With cars, there are more circuits, therefore a bigger single fuse would be needed, it would work, but it is not the best solution as it would also dictate the size of all the downstream wiring as well, there is also the space to put a box with lots of circuit fuses within it which is the better option allowing smaller lighter cable to used.
This might be mumbo jumbo to many but the best advice is = Fit a fuse in either side and of the correct rating and all will be well, replace fuse = cheap, replace bike / garage = £lots.
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