Hitchcocks Forum

I have replaced the fuse holder on my 2003 Sixty 5 with a waterproof one using a standard 20amp blade fuse which does seem a bit high I think Micheal worked out it would draw about 14 amps with every thing on. I have been looking at a wiring diagram which seems as near as means little difference to mine(I had a no power fault I had power to the ignition switch but not seemingly to the ammeter I found the neutral coloured 2 point connector on the ammeter side not connected properly not sure if the speedo cable which is tight popped it open or I did when tinkering but that is another story I will stop waffling!)But while looking for information and looking at the wiring diagram it seems as though the headlight runs directly from the alternator using AC hence even with a new battery ( The old one was the original and the cells shot when I bought the bike about six weeks ago)The brightness increased with rev's and with the engine off no headlight which had me head scratching at first!Does any one know how this will effect the fuse as power for the headlight does not go through the main fuse I recon there should be ample spare capacity on a 15amp main fuse to run the bike with everything on? Advise most welcome please.

If you headlamp won't light unless the engine is running, then it is AC.

Yep thats what I figured, And that being so I recon I should get away with a 15amp main fuse considering other posters saying the wiring was there to protect the fuse! I must admit I have never seen anything like that before with an alternator!

the wiring was there to protect the fuse !!!!!, No the fuse is there to protect the wiring, A 15 amp fuse will let 180 wattage through it but the wiring has to let more wattage through it to protect it. Going back to the melted wire topic most wires on the R.E. cannot handle high wattage and should have in-line fuses.

Err, Jaffa, I think the "wiring to protect the fuse" quote is supposed to be a joke - a comment on the "not brilliant" electrical systems on these bikes.

Ahem... what he (the last guy) said! Also, a 15A fuse will let 180W pass @12V (the critical bit here is that P = IV). When running there is more like 14V available which pushes power to around 210W. When overcharging (like my bike was) there was more like 17 or 18V available (oops!)... hence melty wires. But, back to the point, it looks like 15A will be fine for your bike, especially if the headlight (pretty much the biggest draw) is on a separate circuit.

There are two good practical methods.



The first is to put an ammeter across the fuse terminals, having removed the fuse first. Unfortunately, most electricians multimeters only handle up to 10 Amps, so this can be a problem unless you have a higher capacity meter or one of those ones that just clip very the wire and read it by electro magnetic field.



The other is to start with a low fuse value ( say 5 to 10Amps) and having taken the next few values upwards, start your bike. If the fuse blows with lights, brake light and engine running at speed, then you proceed to the next higher value fuse. When it seems that the current fuse value is not blowing then ride the bike somewhere so that you can run the engine at speed with load (not just rev the poor thing in on it's centre stand. (take fuses and tools needed just in case. Then physically check the fuse. If it is cold, then you should be opk with that value, however if it feels warm or hot, or shows signs that it is not happy, then change for the next value up.



Always carry a spare or two, plus one of a higher value to be used on an 'emergency get you home' only!



IF you have an electricians 10 Amp meter, then you can try the following. With all the lights OFF, run the engine at just over tickover until any residual battery charging is done, (ammeter reading slowly drops). Read the value that the bike settles down at. Make a note along the lines of 'Engine and system only' and putting the value from your meter. Next turn on the headlamp, which with a 50W bulb will use 4-5 amps, plus you will have the tigers eye and maybe a pilot in the headlamp shell, plus your speedo and ammeter (if fitted) backlighting. Check both high and low beam, for the higher value. Write down the value as 'lights on'. Turm lights off and try the brake light, again, note the value as 'brake'. You can try the same with the indicator, but due to their flashing, it makes reading a needle difficult, and most digital meters impossible, unless you have a 'hold peak value' button. The easiest way is to check the value of your indicator bulbs (21, or 10 Watt or LED) remeber to add the tell tale of about 2-3 Watts to twice the value of the bulbs (front and back, one side of course!)



TAke the values for 'lights on' and take the value of 'engine and system only' away from the value (otherwise on adding together, we would have the basic engine value twice!) add this new figure to the value 'Brake' and that should be pretty much accurate to the bike running with all lights and brake on. Now add on the value worked out for the indicators. That only leaves the indicator relay not accounted for, but by now, you should have a figure that can be rounded up to the next higher fuse value.



Again, try it out, check that the fuse and holder do not show signs of heating, and take spares with you.

'clip very wire' in paragraph two above should read 'clip over the wire'

Yep Pete it was a joke perhaps just not a good one!!Thanks Micheal for the info I will go 15amps and if it keeps blowing I will post it.The only other draw would possibly be the starter solenoid lurking in the LH tool box but its only an electro magnetic switch so the current draw shouldn't be that great. Some of the cable on the bike and the odd connector seem relatively slim and I suspect may have less than a 20amp rating similar cable I have seen available is rated at about 17amps hence the bad joke about the wiring being there to protect the fuse!!

If you have more than one fuse, then work out what the fuse is connected to, and then either check with ammeter. It is not really practical to try and work out how much current newer bike with ECU's and other electronics make use.



(and so to lunch! Yummy!)