Electrical Problem

[cash1000]

Merry Christmas.

I've got a long standing electrical problem that as I've got a few days off on holiday I though I would have a crack at fixing.

At times the horn on my 2001 V11 RM doesn't go. During the course of a ride it make go or just squeak or not go at all.

When you push the horn button and it doesn't go you can see the rev counter needle drop. Sometimes back to zero other times a couple of thousand revs. When the horn does go it doesn't affect the rev counter. Sometimes the rev counter may not go at all. When the rev counter doesn't go the motor will occasionally briefly cut out. I'm thinking this may be the fuel pump cutting out. When the motor is idling the rev counter may indicate zero revs but if you apply some revs the rev counter will go.

To try a solve this I've cleaned the battery terminals, replaced all the fuses and cleaned contacts. Relays have been replaced with Omron ones. Is it the ignition switch? I cleaned it a couple of years ago but is it due for another clean?

Any thoughts on what cause could be?

Many thanks for any suggestions you may have.

[docc]

Have a go at Relay #2 (counting from the front). Because your (delicious ) Rosso Mandello is an early V11, that current also passes through Relay #1 (front).

 

Be certain you are running  High Current OMRON relays and just treat your little lady to a full set! It is Christmas after all!

 

http://www.v11lemans.com/forums/index.php?showtopic=19755&p=216605

[swooshdave]

I can count the number of times I've used a horn on a bike with one finger. And that's only because I accidentally hit it.

[moto fugazzi]

There's so much happening in those circuits, that you may want to add a separate relay and new horns. The factory horns are weak at best, and most upgraded horns will require a relay anyway. My original horns only seemed to work when they wanted to, not when I wanted them to...

Ken

[docc]

Flinky horn and flinky rev counter? Hm. Same relay(s). Or their base connections.

 

Fuel pump is on an entirely separate wiring harness.

 

Another fail point could be the battery voltage and charging (although, charging also depends on Relay 2) .

 

cash, which OMRON did you install?

[Chuck]

Have you cleaned the contacts on the horn itself?

[Kiwi_Roy]

The early VII had the first two relays in series Start & Headlight so your lights will also be flakey.

The Horns, Tach and Voltage regulator are fed from the headlight circuit also, so your charging and lights will be flakey as well.

I suggest you measure the Voltage while you try the horn, I'm fairly certain you are loosing Voltage at the start relay.

The horns put quite a load on the circuit exposing any weak connections.

The brake lights will also load down the circuit.

 

One place you can easily measure the Voltage is at the red/black wire going to the Voltage regulator male/female plug.  Connect your multimeter or a test lamp to the socket and chassis while you try the horns.

The Normally Closed contact 87A of the Start relay is not as robust as a Normally Open contact. the Voltage should stay at 12 Volts while the horns are sounding.

Make sure you re-connect the regulator afterwards or the result will be a flat battery.  (I'm assuming you have the OEM Voltage regulator)

 

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

Look at the red wire going to the right most wire of the Voltage regulator, trace it backwards to see all the things it effects.

Trace the branch up to the source, Headlight Relay and across to the Start Relay, fuse 5 and battery.

 

Look at the relay bases carefully, I have seen it where the contact was pushed out the back and just making contact by the spring in the wire

Wrap a tiny wire around the relay pins so you can measure the Voltage coming out, concentrate on 30, 87 & 87A

The spade contacts can be removed from the relay bases and tightened, they are released by a sliver of metal poked into the little cut out in the socket hole.

|-----------|

|----__----|  pardon the crude sketch

       ^-------- contact release

 

When the rev counter is not working the battery will be going flat so it's cutting out on low Voltage, hold your hand in front of the headlight, you will find that out also, you must get that sorted, again I'm assuming OEM Voltage reg.

 

Did you apply Vaseline to the battery terminals, if not scrape them clean again and apply some.

 

Don't give up until you can sound the horns every time then like Moto Fugazfi I suggest you fit a pair of good cheap Italian Fiaam Freeway Blasters with their own dedicated relay fed directly from the battery through #14 wire and a fuse. Route one of the original horn wire pairs to pick up the horn relay coil. Make sure the Fiaams are self draining or a few drops of water will damp them down to a squeak until they dry out, ask me how I know.

 

When you find the source of the horn problem the charging and lights will work better also.

[emry]

Sounds like a horn driver that is stuck. When it gets stick it causes a direct short ( or near that) and pulls the voltage on the circuit low. 

[GuzziMoto]

Sounds like a horn driver that is stuck. When it gets stick it causes a direct short ( or near that) and pulls the voltage on the circuit low. 

It sounds like what emry said. If the tach is screwing up when the horn fails, it sounds like the horn is shorting and dropping the voltage enough that the tach goes wack.

[Kiwi_Roy]

The horn wouldn't be able to drop the Voltage unless there was some serious resistance in the circuit.

The battery should be able to put out 200 Amps while cranking, you re not going to pull that down through the 15 Amp circuit fuse.

Sometimes the horn goes, don't you think its more likely an intermittent bad contact but what do I know?

[emry]

What the battery can put out is illrelevent, the total circuit resistance is the important consideration. If the fuse has 0.3Ω, the relay 0.8Ω, the button 0.4Ω and the horn 0.1Ω, what happens in that fused circuit. 

[Kiwi_Roy]

What the battery can put out is illrelevent, the total circuit resistance is the important consideration. If the fuse has 0.3Ω, the relay 0.8Ω, the button 0.4Ω and the horn 0.1Ω, what happens in that fused circuit. 

What happens, it doesn't work very well, not a good design is it?

The horns do pull a lot of current, that's why they really need a relay and dedicated supply to work properly.

I was simply pointing out you are not going to pull the battery down, its too powerful to be effected by anything that will pass through a 15 Amp fuse,

The normally closed contact of the start relay is a weak point, it is only held closed by a weak spring whereas the normally open is held by a relatively strong electro-magnet.

There are two relay contacts in series on this model. n/c Start and n/o Headlight

 

I know from owning a similar bike that the headlight circuit is weak, I would get between 0.6 and 1 Volt drop at the Voltage regulator thats with the 4 Amps the headlight draws 0.15 - 0.25 Ohms

Much of the resistance is in the relay base, wiggle the relays around a bit and the Voltage drop would reduce.

I suspect the bike in question has even more Voltage drop, that's why the tach drops down when the horn is pressed, the headlight will be dimming as well. 

Battery Voltage will be all over the map if it still has the OEM style regulator.

 

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

 

I doubt this bike will ever suffer from Startus Interuptus though, notice how the start relay is fed direct from the battery,

Not through the ignition switch and all those connectors like the later models

I'm not sure where they took a step backwards, 2002-2003 sometime

http://www.thisoldtractor.com/guzzi007/schematics/2004_V11_Sport_Catalytic.gif

 

Since we are talking Ohms Law, what happens when you try to pass 40+ Amps thru all that spaghetti?

The starter solenoid has 2 coils in parallel 1.05 Ohms and 0.25 Ohms

[emry]

Roy, it has nothing to do with the battery or the charging system, let alone the changes in resistance to the starting circuit during pull-up. A fused circuit will only move so much current, based on the total circuit resistance, not what the power supply can provide. The problem occurs when the horn button is pressed, how about we focus on that problem and the voltage drops that happen therein. Your wiring diagrams here are awesome and your advice on this site is always outstanding. I wasn't really challenging your aptitude nor trying to dive into discourse about ohms law. 

 

I didn't take the time to look at a diagram in this case, but my advice was based on experience as a long time technician.  

 

To the OP, disconnect the horn. Start it, and press the horn button. What happens? If everything works like it should, replace the horn. While there can be other issues this is a quick and simple starting point.

[docc]

The OP posted these two RevCounter behaviors, independent of the horn:

 

"Sometimes the rev counter may not go at all. When the rev counter doesn't go the motor will occasionally briefly cut out."

 

"When the motor is idling the rev counter may indicate zero revs but if you apply some revs the rev counter will go."

 

Back to asking the OP about Relays 1 and 2 . . .

 

otherwise, we are going down the Grounding Rabbit'ole . . .

[emry]

I get stuck at the third and fourth sentence  

 

I hope everyone here has a excellent new year!