Help! electrical problems
 

I have what appears to be a problem with the wiring that feeds the engine management fuses and relays that are under the seat.Basically whilst out yesterday my bike cut out and after checking all fuses found that the 20A fuse next to the ECU had blown,luckily i carry spare fuses and i replaced the fuse only for it to blow again after setting off. This happened several times until i ran out of fuses which then lead to me calling the AA. When the AA arrived (10 minutes by the way) he suggested that i may have a loose wire thats causing the fuse to blow or have a fault on my fuel pump, he messed about with the wiring but it still kept blowing fuses, then for some reason i tried it again and it worked. I managed to ride the bike home and then luckily as i rode into the garage the fuse went again! After changing it for the umpteenth time the bike started but cut out straight away again i went to change the fuse but it was ok!!! the relay marked N02 was now clicking, tried swapping with the relay next to it but that also clicked . Now i'm well and truly stumped, is it a faulty wire?, faulty fuel pump?, water ingress? any help or advice would be great.
Cheers Rob.

this is doing my head in now, just tried it again now and it appears to be working fine, you know what will happen though, i'll just set off out and it will stop again miles from anywhere!!! if anyone has had similiar problems as to what may be causing this please let me know.

Thanks
Rob

I had simillar back many years ago on my 95 plate 916, it was a headlight connector that kept blowing it with a bad earth. But realistically, it could be pretty much anything or everything..

Well the problem is still there i went out today and got half a mile before the fuse blew,new fuse fitted and just managed to get home as it blew again. spent most of afternoon checking all wiring and connections under the seat and around the bike but cannot find anything untoward. Has anyone got any suggestions as to what is causing the fuse to blow?

elect probs
 

Let me know your exact model mate, and ill have a look at the circuit diagram when i get in from work. (im in the us at the mo, so you may get an answer by the time you get up in the morning).
Dc circuits are prone to poor earths, so check your cables and earth returns to the frame.
Look for any wires which are discoloured, this is a sign of overheating.
When your bike was running, was it running normally, ie lights and all other functions ?

Does the bike start ok, no problems ? does your bike have an alarm, if so which one ?

any accessories fitted to the bike ? ie aftermarket indicators, digi gears, or anything else ? quick shifter.

Think back to when your fuse blew...what were you doing at the time on the bike ?

Any info will help

elect probs
 

according to the diagram i have here, the fuse you are talking about is under the rear section, on the cross bar, and should be a 15 A one...am I correct, as you say its 20A

looking at the cct daig, this fuse protects the ecu and power relays, could be a faulty relay (one of the two right under your seat)
send me a pm with your contact tel no and ill ring you in the next 1/2 hour.

We need to know which model bike you have, with which ecu..then we can be more specific...however check the following as a matter of course :-

1.All connectors, all earths for loose wires / poor connections.
2. All connections to sensors / fuel pump
3. check connector block to ecu
4. check power relay connectors

report back

thanks for the replys Demon, its a 99 748 Biposto, i have swapped around the relays with no effect. I have had a thought though, you mentioned about overheating, yesterday my mate noticed that the temperature gauge was between 180 and 200 but the fan did not come on. Could it be the fan is not working and when the bike reahes a certain temperature it blows the fuse? i'm getting the father in law round today he's a spark and i'll get him to have a look. Will keep you informed mate.

ok, then check the fan thermostat for good function, you say that the fan does not cut in, so a simple test would be to allow the bike to run whilst on the stand and observe what happens, when it reaches the cut in temp.

just tested the fan, the temperature reached 180+ and did not kick in. I then connected a wire from the battery to the fan and the fan works fine. Very puzzled at the minute. I did discover a leak on my expansion tank though, don,t know if that is also affecting things??

So you could have a faulty fan thermostat.
the split tank is becoming a common problem on this forum, and there is a sensor connected to it too..check it over

will look at it now, and let you know,

everything looks ok with the sensor,i'm still waiting for the spark to come with his testing equipment to see if he can fin any problems.

any news ? you've gone quiet !

I have noticed on my 1996 916 that the fan does not cut in until the water reaches 210, whereas Haynes says it should start at 197.

When I get time I'm planning to remove the fan sensor and test it in pan of water on the cooker, to see if it's at fault or if the temp guage is wrong?

No news yet, the electrician has not been able to come round yet. Bought a new expansion tank from Ducati Leeds today and he advised that i renew my fan thermostat and also that my electrical problem could be the wiring around the starter relay. Had a look around it and could not see any damage,could the afaulty fan thermostat be causing the fuse to blow?

in a short answer yes.
Have you looked at your official hanbook wiring diagram for the bike, because the one i have here shows a 15A fuse at that location, yet you said you had a 20A one fitted ?

yes mate looking at my Haynes manual now and it says 20a and 5a fuses.Gotta wait until saturday for my replacement fan thermostat to arrive.

Don't get too worried by a small difference in temps where the fan activates. the temp gauge isn't the most accurate and even a small amount of dirt or a semi loose connection will alter the reading.
I don't think the fan or engine temp is the cause of your problems. The ECU/pump relays are the most likely but any of the sensors going to earth could blow the fuse.
I'd try disconnecting all the sensors and connections on the ECU loom and reconnect each one in turn. if/when the fuse blows then you've isolated your problem area.
I'd also suggest nipping it to your nearest dealer for an interogation by the Mathesis tester. The ECU will return error codes on sensor earth problems, and will hold these in memory.
Could save you hours in tracing the fault.

The only problem Nelly is that the fuse only tends to blow when out on the bike after anything from 1 minute of setting off or upto 10 minutes,it did happen 6 months ago but after changing the fuse twice it seemed to right itself until last week.

fitted the new temperature switch and started the bike but it got to 190+ and the fan did not come on. Cab anyone tell me at what temperature their fan comes on

Rob
fan cut in temp varies on all bikes, by a few degrees, so dont worry too much about that. If it doesnt cut in at all, then there is a prob somwhere else, does the fan actually work if you connected it across your battery ?

the fan is fine i ran a wire from the battery, just wandered how hot it had to get before it came on. been out on bike today and everything seemed ok,never blew a fuse. i would still like to try and get to the bottom of whats causing it though as i think it will happen again.