Author Topic: Fuse question  (Read 944 times)

Pizza Guzzi

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Fuse question
« on: October 03, 2019, 09:08:59 PM »
I went to crank over my Breva 1200 this morning and got the old click no startee routine.  Previous owner had done what I assume is the usual fix of running a fused wire from batt positive to the starter relay in place of the yellow wire from the wiring harness.
Bike has always started well but today the fuse blew in the lead from the battery, it was a 20 amp fuse - does that sound like the right rating ?
I put in a 15 amp fuse cos it's all I have in the shed and it starts ok with that and I'm not sure why the original blew anyway. I've always been told to find the problem rather than chuck in a new fuse but my knowledge of electrons is limited.
At this stage I'm just going to make up a new lead as the one fitted by the last owner is a dogs breakfast. Think I'll just carry a spare fuse and hope for the best but what amp fuse is correct for this application ?

Glenn

pete roper

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Re: Fuse question
« Reply #1 on: October 03, 2019, 10:49:17 PM »
We've seen a couple of starters on Sports play up but strangely not other CARC models. On disassembling them we've found the bushes very dry and gritty which is odd but the greater demand put on the starter because of this seems to up the inrush current demand to the point where the fuse blows.

Try taking it apart and cleaning and lubing the bushes but be really careful removing the planetaries as there springs and cogs that try to jump out everywhere!

Pete

Pizza Guzzi

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Re: Fuse question
« Reply #2 on: October 03, 2019, 11:30:21 PM »
Thanks Pete, that might just be the culprit, I'll have a look at that.

Glenn

Online Kiwi_Roy

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Re: Fuse question
« Reply #3 on: October 04, 2019, 01:50:50 AM »
With a direct connection like that the solenoid is probably pulling 40 - 50 Amps but just for a split second.
HOWEVER if the main lead to the solenoid is loose or has a build up of lead oxide on the battery terminal the 20 Amp fuse will blow in seconds because the split second of 40 - 45 Amps doesn't drop back down to 10 amps holding current as it should. (Look at the note against the wire from battery + to solenoid on the sketch below)

I suggest you remove the battery leads, scrape the terminals to show shiny metal then apply some Vaseline to prevent the Oxide build up.

Lead Oxide is an insulator, it can disconnect the battery lead even though the bolt is tight.

Most Guzzis have a 15 Amp fuse fitted but I believe a 20 is more appropriate for the high inrush current


Here's a sketch I did years ago to explain the current inrush that causes Status Interuptus




Note: This shows there are 2 coils in the solenoid, None of the Guzzi Schematics show that, The Bosch starters and the Chinese ones fitted to V7s also have 2 coils, I'm sure this also applies to the 1400 Californias.
« Last Edit: October 04, 2019, 02:24:41 AM by Kiwi_Roy »
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Pizza Guzzi

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Re: Fuse question
« Reply #4 on: October 04, 2019, 06:29:30 AM »
Thanks Roy I cleaned up the battery terminals and applied Vaseline as you suggested. I also replaced the lead from the battery to the starter relay as the old lead was a real POS.
I think I'll put on a 20 amp fuse per your advice.

Glenn

 

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