Intermittent Tachometer

[Dr Gil]

This morning during my morning daily commute (20 miles) I suddenly lost my tachometer. It registered zero RPM.

 

While I was swearing at the almighty Guzzi-gods it suddenly sprang back to life...for a minute. Then it went back to zero.

 

It did this a couple of more times during the ride but never worked more than for a few seconds. When I parked it at my job it was not working. At the end of my work day imagine my shock when the tach is suddenly working again. The bike has not moved nor been touched for 11 hours. I lost the tachometer one more time for about 30 seconds on the ride home then it "came alive again" and worked the rest of the way home including a shut down for fuel and over rough roads.

 

I am not sure how my tachometer works. I assume it's electric but have no idea if it's tied to the engine (or where on the engine) or to the transmission.

 

My first suspicions are some sort of sensor is going bad (sensor?) or I've got a connection working loose (damn vibrating sons of bitches).

 

Can anyone more knowledgeable help me out with a few suggestions about where I might start looking and what I'm facing here? I am also suffering other electrical issues (intermittent oil light, neutral light and an alternator light that's on more than I like) but don't feel they are related.

 

I NEED my tach.

[docc]

The tach is electric and triggered by the ECU. It is common to get a sketchy ground inside the instrument. Do a search as calisson had posted a handy fix.

 

With the other lights intermittent as well I would not rule out some relationship. The terminal stacks on the battery should be checked for tightness (easy) and the connectors along the frame toward the front of the tank (less easy) pulled,cleaned and lubed.

[Guzzi2Go]

Exactly the same happened to me on Sunday, with the exception that the tach did not come back to life again. Now it is just plain dead.

 

BTW, it is a white background Veglia instrument. If I can recall correctly, it is "powered" by a rectangular pulse (works like a counter/frequency meter). Where does the pulse come from, not sure. Will open and find out.

[stogieBill]

Sure sounds like a bad connection, Doc. Damn salty air around here.

[mdude]

I've gone through this the last month. Loosing the tach was for me an early sign of a serious contact problem. which in turn led to a total loss of lights and power. Its difficult to source excactly where the fault is but this helped me:

Take the tank and rear bodywork off and go through alle the switches and contacts you can find, especially those sitting on the spine itself. Take them apart, clean them and check them all, then put a healthy dose of contact grease in them when putting them together. Check all wires, fuse connections and relay connections. Check the bulbs, change them if you have spare, sometimes a short wire can occur in a bulb. Its a two hours job, but it will probably do the trick.

Theres also a dubious earth connection going from the tach, it might be worthwhile checking this also, I didnt cause it all works fine now....

[Dr Gil]

Update: (with all new clues!)

 

So now I'm on day 3 of this on again/off again tachometer. Each day I loose the tach about 1/2 way into my morning commute. Each day I park the bike at work with the tach not working and each day (after sitting in the sun under a cover) after work the tach is working again and works all the way home.

 

The only difference between the morning and afternoon commutes are temperature and moisture. I suspect the moisture is causing some sort of electrical anomaly (the temps here on the coast don't vary that much).

 

Which brings me to today. This morning the tachometer started off working as it generally does and then as I neared the 1/2 way point and then I noticed as I used my turn indicator that the tach would drop about 2K rpm every time the turn signal fired. I'm doing 4,000 rpm, no I'm doing 2,000 rpm, no I'm doing 4,000 rpm...you get the idea. A little further down the road it failed completely only to come back on for the ride home.

 

Another thing noticed about the turn indicators is that they are much more sluggish than usual. They used to come on immediately when the switch was operated...now there is a lag. I flip the indicator button and it's 2 seconds before the signals react.

 

I now know the problem is electrical. I know I'm going to have to start sorting out electrical connections (I hate sorting out electrics) but I'm hoping with this latest bit of info someone can give me some sort of idea where I might start. The problem seems to lie somewhere where the turn indicators and the tach share a circuit.

 

Any thoughts or advice will be greatly appreciated.

[Guest ratchethack]

Gil, this sounds to me like classic ground path symptoms. You've undoubtedly got a ground connection that's started to corrode. The good news is that when you find it and brighten it up and add dielectric grease, it'll likely be the end of the problem. Since I don't share the same year or model Guzzi and have different components, I can't be specific, but I've preemptively added ground wires to the tach and everything on the fork on mine, so no ground path is forced through the steering head bearings. Just a thought.

 

Carl Allison has done great write-ups on tach ground paths, as Docc mentioned above. You might do a few searches.

 

Good luck.

[Daniel Kalal]

on my Daytona (being the 1st spine; possibly similar wiring) the turn signals and the tach are on the same electrical circuit (and are therefore protected by the same fuse). Recently a floppy turn signal wire (nominally tucked into the fairing) touched to ground, which knocked out the tach... That's not to say yours is the same problem, but this is the sort of simple item you're probably looking for.

[Guzzi2Go]

Ok, I opened.

 

Found nothing!

 

From the material available on the internet, and on the little sticker on the side of the instrument, the "contagiri" should point to 11,000 rpm when receiving 366 12V (+/- tolerance) pulses per second. I applied my pulse generator on it. Nothing. It looks like it has rattled itself to death.

[Bbennett]

Yes, my Veglia died at 12K miles and now my replacement sometimes does not work for 3 seconds or so - a grounding problem but I cannot find it. I decided to live with it, it really harms nothing.

[motoguzznix]

The current for the tach has to pass the starter relay and the light relay. I would check these first when the tach fails.

 

When the head lamp and the idiot lights work while the tach fails, it is supposedly not caused by the relays.

[dlaing]

The current for the tach has to pass the starter relay and the light relay. I would check these first when the tach fails.

 

When the head lamp and the idiot lights work while the tach fails, it is supposedly not caused by the relays.

Although it is more likely the ground, if your headlight goes out when the tach goes out, you will know it is the relay, so it is easier to check then a bad ground.

Note that if that relay is going out, then your charging system will also go out, possibly causing turn signals to weaken, etc.

Regardless, you might consider the headlight relay conversion where you run a direct hot and ground to the battery and put a couple relays in the headlight bucket to send more better power to the lamp, bypassing most of the current past the notorious starter relay.

Come to think of it, my Tach may flutter less since I did the relay bypass surgery???? But could just be wishful thinking

[Dr Gil]

Update:

 

Ok, I spent about 4 hours on Sunday tearing the front of the bike apart. I pulled the seat, the plastic and the tank off...all was revealed.

 

Nothing was obviously out of place so I spent my time meticulously cleaning all the build up from numerous mysterious oil leaks (another thread and I think I can safely say once again "problem solved") and opening up, cleaning and coating with dialectic grease ALL the connections I could find...including relays, battery, turn indicators (both bulbs and innards).

 

The good news is that my tach hasn't quit since the operation. The not so good news is that that is no indication that I've cured the problem.

 

While down in its bowls I did take the opportunity to clean the K&N air filter and re-oil it and did change the spark plugs (bike's running rich...must get it to a dyno and set the Power Commander) and must say the bike is running sweet !

[Dr Gil]

For the love of...

 

On this morning's commute the Guzzi's tach quit on me again...sooner than usual however. I got 19 miles into my 20 mile commute and suddenly the bike starts stuttering, loosing speed and then quit altogether. I pulled over to the side of the road and stopped. I turned the ignition off then on, hit the start button and NOTHING! I thumbed the kill switch off and on and still nothing. A passing co-worker gave me a ride to the job.

 

Several hours later I went back to the bike and tried to start it (hoping it was just dampness that had shut it down) and the engine turned over but wouldn't start and then the starter just clicked. Dead battery. The battery was replaced about 6 months ago.

 

I towed the bike home after work and put it on the battery charger. After a couple of hours I went out and tried to start it and it fired right up and ran strong. I put it back on the charger and went to bed (long day).

 

I have now shifter gears in all this and am no longer thinking I have a short/ground problem but have a charging problem instead. My alternator light will flicker at times at low RPMs around town or at idle but goes away with increased engine speed. I have had no other indication that anything was seriously amiss.

 

Am I right in my thinking it's a charging problem? Any thoughts?

[docc]

Time to out the digital volt meter on and take readings: off, idle and at 2000-2500 rpm.

 

Be certain the connections from the alternator (yellow wires) are clean, tight and well insulated.