is this the infamous Relay failure ?

[jihem]

Hi all,

 

I did a quick search but couldn't see if it had been described here before...

 

My Supertwin is blowing the starter/lights fuse every day. Sometimes it will happen 5 minutes after "take off", sometimes 1 hour later.

We somehow traced down a possible problematic situation and changed one of the cables, but still, the fuse blew later that day.

 

When there seem to be no more conflictual problems with the cables, everything seems correct and within working parameters, can it be that the relays are in fact the problem ?

[Kiwi_Roy]

I doubt its a relay for the fuse to blow needs a short circuit to chassis, possibly a wire pinched somewhere.

Since your bike is a special it may not have the standard wiring, do you know?

If your wiring is non standard pull the fuse and make a list of all the things it effects.

So it happens as you are riding, not when starting.

Does it happen when you apply the brakes?

 

One way to look for an intermittent short is to replace the fuse with a lamp, then wriggle all the

wiring around if the lamp suddenly becomes bright you are on to it. Far quicker and cheaper than

blowing fuses, I use an old headlamp bulb for this purpose, the normal load will make it glow but

not at full brightness until you get the short.

I would start by checking the wires going to the tail light area.

[jihem]

I doubt its a relay for the fuse to blow needs a short circuit to chassis, possibly a wire pinched somewhere.

 

this has been examined already. all seems fine.

 

Does the fuse blow while you are riding or only when you are trying to start?

 

the wiring seems standard. Fuse blows while riding the bike.

 

One way to look for an intermittent short is to replace the fuse with a lamp, then wriggle all the wiring around

if the lamp suddenly becomes bright you are on to it. I use an old headlamp bulb for that.

 

interesting....

[HaydnR]

Could be the regulator/rectifier gone faulty.

[jihem]

Could be the regulator/rectifier gone faulty.

 

 

Would a regulator act like that, sending sudden bursts to the fuses now and then ? And always blow the same fuse (starter/lights/tacho) ?

Wouldn't it just stop working instead of being temperamental at times ?

[HaydnR]

Could be the regulator/rectifier gone faulty.

 

 

Would a regulator act like that, sending sudden bursts to the fuses now and then ? And always blow the same fuse (starter/lights/tacho) ?

Wouldn't it just stop working instead of being temperamental at times ?

 

 

Yes,a friends 2002 le mans was popping fuses whilst riding. He took it to his usual mechanic who took it for a run with a meter attached and diagnosed the r/r fault which he replaced and then all was well. I suppose you could prove it by disconnecting the r/r (fuse3 30a) and see if the fault goes away.

 

edit: just spoke to Harry who had the problem above and it was always the 15a fuse 5 that was blowing.

[Kiwi_Roy]

I really doubt it's the regulator, you can eliminate that by unplugging the Black/White pair of wires a

few inches from the regulator, just be aware that the bike won't charge with those out. Unless the

regulator melts down there is no direct path to ground from Fuse 5.

 

Fuse 5 supplies a lot of wiring with potential short capability (the Red/Black wire) goes all over the place.

It supplies Tacho, horn, panel lights, stop lights and also acts as the voltage reference for the regulator.

http://www.thisoldtractor.com/guzzi007/schematics/1999_V11_sport.gif

 

One thing I would check carefully is the idiot lights, the lampholders are absolute c***. They short out if the wrong lamp is inserted. Ask me how I know. You can eliminate those by unplugging the connector (8) or snip the common wire.

 

Does the fuse blow when you are not operating anything or would you not notice the headlight going off?

 

Check both stoplight switches.

 

The tail-light wiring is a very common place to get a short, where the wire passes through a fender or the lampholder itself, have a close look at that. Even the lamp can short out. The stoplight is fed from the same fuse.

It's a simple short somewhere. Google Carl Allison Drawings and get the appropriate print then just follow the red/Black wire around.

 

If that fails to find anything the next step is to divide up the load, hopefully it won't come to that