Blowing main fuse - HELP!!!
 

I recently replaced the gasket (ignition side) on my Tenere (1984) due to it leaking oil.
Everything went OK till a few days later. I got the bike out and it wouldn't start. I then noticed the lights were not working. I checked the main fuse and it had blown.

I replaced it thinking everything would be fine but as soon as the ignition was switched on it blew.

I have traced the fault to the ignition circuit, when the CDI is disconnected it doesn't happen.
I had a spare CDI to hand so I tried that and the same thing happens.

Has anyone had a similar problem?
How is it fixed

Basically I'm at a loss - I'm an electrician and it doesn't make sense to me.

Well I'm not an electrician :) but my guesses are:

1. Two duff CDI units - unlikely but possible

2. Fault in the wire to the CDI or the connector, thus showing only when the CDI is in circuit.

But that could all be b*llocks, of course.

you need to take the cover off and re check there first sounds like a pick up wire has been dislodged and rubbed through to short out

I disconnected the wiring from the pick up while I was looking earlier and it didn't make any difference.

It is deffo the ignition side of things that's at fault.

Any more ideas???

disconect the 6way at the cdi if it blows then you need to a continuity check between the cdi plug and that pickup conector then check its not shorting to earth thats the only thing that would blow the fuse other than the cdi being faulty

hi tom, not an easy problem to solve it sounds like a live wire is earthing somewhere try disconecting one be one all switchs etc . also are all the earth wires ok . get the multimeter out and put the kettle on, and get a bag of fuses in . good luck zigzag

Cheers guys - you are all talking sense!!!

I'll be getting my meter from work tomorrow and will have it sussed out before long.

Look forward to seeing you at Squires soon Gaz:thumbup1:

It's looking like there is a fault on the loom.
There's a dead short on the +ve and -ve (battery terminals) when the ignition is switched on.

I checked the main fuse that had blown and it was a 30A which seems a bit high to me.

I'm thinking there's been a bit of melting plastic going on in the loom and 2 cores have become in contact with each other.
Until I get some more time to sort it I'll be riding my lads moped :scooter:
27mph!!! It's getting de-restricted as soon as possible too!!!

hi tom the fuse or circuit breaker is only rated at 10 amps so to blow a 30 amp fuse some thing might have been iffy for a while , i hope the wires are not fried too bad and its not total meltdown ,good job your a sparky zigzag -----27 mph so no speeding ticket tom , peddle faster mate

Old joke: at least you won't get done for speeding, but you might get arrested for kerb-crawling.

Boom-tish.

:(

tom you said "when the CDI is disconnected it doesn't happen"
is this no longer the case if so give details and i should be able to point you in the right direction as i've been working with auto electrics for nearly 20yrs

Yep that's right. I also disconnected the earth on the coil and it stopped too.

"I also disconnected the earth on the coil and it stopped too"

that is rather missleading i think it possibly a short in the loom where it runs from the cdi down the frame about half way down the length of the seat, check for signs of rubbing through and heat damage.

i'll dig out the wiring diagram later and do you a test sequence to follow if you cant see anything obvious on the loom.

I'd have to agree with you - I'm going to disconnect everything from the loom and check the insulation between the cores. I'm pretty sure it will be a short somewhere.

mine had rubbed through where i said and had damaged the wiring to the reg/rectifier, but depending on the twist in the loom might rub through the cdi wiring.