Fuse 'B' (and maybe 'C') blowing on start

Soon after I got my bike, on starting up fuse ‘C’ blew [EDIT: might have been ‘B’, see later in this thread] so no start. On replacing that with a good fuse, bike ran fine… but same thing happened yesterday. Anyone else come across this? Any ideas what is causing it (fuse ‘C’ is 15A as it should be).

GZK6NK2013-08-07 17:06:51

could be a sticking piston in the starter motor, that sometimes raises the current and pops the fuse
i cleaned mine out and lubricated it with graphite

According to the wiring diagram, fuse ‘C’ feeds the fuel pump, the injectors, and the coils.Has anyone else had this problem?

Did you look in the FAQ section before posting? The starter problems are clearly documented in there with full details of the fix.
Are you certain it is fuse C? Normally it’s fuse B which controls the start circuit and rear light.When the fuse blew, did the starter motor turn? If not then it is definitely fuse B.
Brian UK2013-07-29 09:22:10

I saw the fuse ‘B’ posts. This is deffo fuse ‘C’. The starter motor starts to turn for a fraction of a second before the fuse blows, so the contactor must be pulling fully in. I suspect the ECU senses fuse ‘C’ failure, and inhibits the starter from running once the fuse has ‘gone’.

I hate these intermittent faults. Need to find out what keeps doing it until it’s found and fixed.

Could be at easiest a faulty fuse box , had that on the V11 the fuse contacts corroded then burned away blowing the fuse OR bad connection or faulty relay IF you are lucky

How old is the battery, as the battery voltage drops under load then the amps drawn increase, basic ohms law if the bike has been stood for a long time unused like your had before you bought it then I would bet its the battery on its way out
Regards Keith

I’m wondering the same. It’s 4 years old and had only done just over 1K miles when I bought it recently. Each time the fuse has blown it’s after the bike hasn’t run for a couple of days (it always - so far - restarts OK when out on a ride). Before I start it next time after a lay off of a few days I’ll stick the Optimate on it first to get a full charge, then try it.If I consistantly get no problems with a fully charged abttery, but fuse failures if it hasn’t run for a few days, I’ll consider a new battery.

To reiterate (sorry), fuses don’t blow for no reason, summat’s up like a overload or intermittent short somewhere, fiddling with batteries won’t help.

Arrgh! Another fuse blew on starting - checked carefully before replacing, and …it’s fuse ‘B’! Could I have been wrong about the other fuse blows? Was it ‘B’ all along and I was looking at fuse box from the wrong end and thought it was ‘C’? Or are they both blowing?I’m going to assume for now that I’m an idiot and has been fuse ‘B’ all along. Unless fuse ‘C’ really does blow in future! I hope it is just ‘B’, as that at least seems to be well understood. I think!Voltage is reduced through the ignition switch and its small diameter wires by the current needed to pull in the starter solenoid, and the reduced voltage to the starter solenoid means the current goes high enough to blow fuse ‘B’. This can be made worse by a sticking starter solenoid which means the pull-in coil is on for longer that it should be (it should be relieved almost immediately by a lower current hold-in coil if all is working correctly?).But if fuse ‘B’ can power the ‘pull-in’ solenoid at all, it should surely be capable of supplying ‘pull-in’ current for any length of time. So is the ‘sticky solenoid’ issue a red herring?

No, DC resistance of winding is extremely low, virtually a short-circuit (if my Bosch one is anything to go by), it’s the inductive reactance that controls the current, this climbs from zero until there’s enough magnetism generated to move the plunger, THEN of course it’s switched over to the holding winding. The latter is much higher resistance so that is the one that can be powered up indefinitely. This has to happen in fractions of a second else the current rises too high and could blow the fuse. The fuse, of course, is there to protect the wiring and connectors. So could still be ‘sticky solenoid’, maybe need to open the starter motor for a looksee ?

What’s involved in removing and cleaning the solenoid? Is it straightforward? I’ve bought a Griso manual but it’s pretty useless on stuff like that.

If it’s a Valeo found some instructions here: http://www.threecountiesguzziclub.pwp.blueyonder.co.uk/DOWNLOADS.html

take it to your local auto electrikery specialist

I don’t think so. I shall fix this myself… I do know a bit about electrikery; in my experience with other vehicles, more than many so-called auto specialists. But if someone else who is Guzzi experienced has already ‘done it’, then I’m willing to learn from them rather than ‘re-invent the wheel’.However, I am not yet familiar with the ‘nuts and bolts’ of the Griso regarding disassembling mechanical assemblies (only recently bought it), so am grateful for the help on here of those who are. And as I get experienced on Guzzi specifics, I’ll be happy to share that with others here.S’why I joined the club!
GZK6NK2013-08-04 20:46:37

I’m fairly sure it will be a Bosch starter, the one on my Norge is. Before anyone jumps in, do not compare this with the old Bosch starters. Very easy to do. Disconnect battery.Two bolts hold the sterter to the crankcase, just unscrew them. At some time you will aslo have to remove the connections from the solenoid, sometimes it’s easier to do once the starter is unbolted. Then just remove starter motor.You will then see two Torx (star) screws which you undo, and the solenoid housing will slide back leaving the plunger fixed to the operating arm.Clean sticky grease from plunger and inside of housing, then put a smear of engine oil in place of it.Reassemble as it always says in the Haynes books. Interestingly I blew the starter fuse on the Norge last week, and I had done the bypass, the new direct wire does have an inline fuse (20A). Changed it and the new one blew. Put in a 30A fuse and that held, but the starter did not engage. Turns out the teeth must not have been meshing,which did not allow the solenoid to complete its travel. Ended up removing starter, checking it, then putting it back and all was well. S’why I joined the club! And that’s what we are all here for too.

Thanks Brian. I did that today, except my starter motor solenoid has 3 Torx screws, not 2. There wasn’t too much grease in there, just a very light smearing. I cleaned it out anyway and smeared the plunger and the inside of the cylinder with a bit of new engine oil on a clean cloth.Has started OK since - let’s see if that has cured it… although I don’t like the idea of the solenoid current going through the ignition switch so will do the mod anyway. When I figure out how to get the rear side panels off the bike to access the relay (see other thread)!I am noticing that any fasteners I take off are ‘dry’, and the lower starter motor mounting bolt had a little corrosion on the shaft and in the threads. So every fastener goes back with a smear of Coppaslip on it.

I always grease every screw/bolt/nut I can find whenever I do anything on the bike.Did you note the make of the starter? Mine was a Bosch one, yours may be different.