Rectifier and fuse.

I'm not surprised it blew at 3 Amp............If its the one I'm thinking of, it should be 30 Amp.........

....but I am basing that theoy on Ess-ess wiring......

AL

 

Nelson, which bike? There is no fuse on the reg/rec on a 748 and the 3A fuses in the fuse box are for the RH and LH switches on the bars.

 

On the early single phase 748 and 916 there is the fuse you show. It goes to the regulator, it must provide an ignition reference voltage, but it also tees to the kill switch and starter button. If it blows there will be no starter function and no power to the ECU. Hence the dead bike.

 

Sorry, I've no idea. It could be a bare wire causing a short, a faulty component or maybe the fuse just died of old age.

 

Hi. The current in a circuit is directly proportunal to the amount of voltage and resistance. If one changes then so does the other. If the resistance in the the new regulator is the same as the old item, then the increased voltage output would increase the amps. If the new reg has less resistance and a higher output than the old one then the amps could go up a fair bit. All a bit hard to say without knowing old and new measurements but the long and short of it is, yes. Your changes could be the reason the fuse blew. If you have an multimeter, set it up for amps, remove the fuse, put one probe in one side of the fuse holder and obviously the other probe in the opposite side. Fire the bike up and see what it's reading, maybe give it a rev too to get the most out the charging system. If you get more than 3 amps, no good

 

Nelson, what Derek said, I thought you had a 99 748 for some reason. So it runs OK until you were giving it a little? Does it run at 14.4 all the time or does it run closer to 14v most of the time, 14.4 after starting or on the fast idle, does it drop below 13 on very slow tick over? Is there any evidence of heat on your new wiring at the two (formerly yellow) alternator to rectifier wire connectors?

 

Hi Nelson

I'm the first to admit I don't know the bike that well. I tried to get a wiring diag for the 916/748 but the quality was pants and I couldn't read it properly. I ass-ume that from Denzl's post its a permanent magnet alternator probably 2 phase if 2 yellow wires. Would think that your new reg/rec has a slightly higher volts setpoint or the old one has just become tired and possibly drifted over time.

Remember its a 2 function jobby regulator whose job is to hold the Volts at the correct level and if too high disipate the excess power through the unit as heat and rectifier whose job is to iron the squiggly electricity (AC from the alternator) to straight electricity for use on the rest of the bike (DC). The rectifier probably also has better Diodes making it more efficient at Ahem, electrical ironing.

I wouldn't think anything upstream on the Alternator side would cause the fuse to blow, the output will be more or less fixed at any given rpm and as you said it was only when you started to give it stick that the fuse blew it might be the regulator is set maybe a fraction high, some are adjustable.

However I wouldn't worry yet especially if its been running the original fuses for many years. I'd replace it with a new one and try it. Could well be the fuse just isn't up to the hew higher voltage and as 1037 stated proportionally (marginally) higher current from the new unit.

I'll probably get shot for saying but if the 3A blew after a while and not right away I'd bung in a 5A and try it. I would doubt the wiring is sized that critically. That is just me though.

Sorry if I am teaching my granny etc etc:

Denzel sure is the gnu when it comes to all things electrical with Ducs

John

 

Remember its a 2 function jobby regulator whose job is to hold the Volts at the correct level and if too high disipate the excess power through the unit as heat and rectifier whose job is to iron the squiggly electricity (AC from the alternator) to straight electricity for use on the rest of the bike (DC). The rectifier probably also has better Diodes making it more efficient at Ahem, electrical ironing.


Old jock

I like your excellent explanation of the way the 'squiggly' AC is ironed out to DC

You would make a great teacher!

 

Crystal John
Thanks for the compliment but God forbid I teach any "weens" (as we'd say in Glasgow). Being a simple soul I try to explain it the way that I understand it.

Nelson
Providing you are using a 3 phase rectifier (reg/rec) that's up to handling the power it shouldn't make a difference the concepts are the same. Permanent magnet alternator means fixed output at a given rpm and output rising with rpm. The excess power has to be dissipated as heat by the unit.

If the reg/rec wasn't up to the job you'd just probably fry it, so I don't think that's a problem.

I'll let Denzel confirm but the voltage sounds about right, 1098 is 14.5 at 3k rpm, nearly all bikes should be about the same.

Pretty sure that wire for the regulator is as others said a voltage sensing wire. On the 1098 set up its fused through the 30A main fuse. On the 1098 it appears that the voltage sensing circuit is directly across the battery. Is it the same in your set up? I'm just thinking on the probability of any resistance in the sensing circuit, if there was it would cause the regulator to errrr regulate at a slightly higher voltage.

Check all your main battery connections and grounds are good as this will do the same thing. Replace the fuse and go ride.

Just my tuppence worth

John

 

Classic

 

Nelson, the plot thickens, you have a three phase 1098 alternator, which regulator is fitted?