Another Tach Failure

[Guest ratchethack]

Well, the infamous Veglia tach just took a catastrophic dump. Symptoms - today it suddenly went from months of relatively benign, vibration-induced, mild variance (but only between 5-5500 RPM) right into a couple miles of erratic, jumping all over, then directly to dead quacker (er, honker maybe?)

 

Question: I've got the instrument out on my bench. Didn't I read here a while back either a post or a link to a procedure to pry off the bezel and install a good ground inside the case, which is the #1 most likely culprit?

 

I seem to recall it was Carl A's...? My searches somehow didn't locate it.

 

Anybody got the link? And Carl, if you're out there - any updates on this?

 

Thanks in advance!

[al_roethlisberger]

All I did was to splice into the ground wire, and add another ground wire with an eyelet and bolt it under one of the couple screws/studs on the back of the tach. The problem is simply that the original case ground under the stud often works loose, so two is better than one

 

That cleared up my ground problem... which may or may not be your problem.

 

But I'd try that first.

 

al

[callison]

Al's approach should work until the second stud breaks loose. Tach failure occur for other reasons as well, but the starting point is to remove it from the bike and wiggle the case mounting studs. Hopefully, that's all there is, as that is a tedious, but cheap fix. If the IC is fried, there are no commercial equivalents for it that I've found.

 

Here's a past post of mine from another forum.

 

-------------------------------------------------------------------------------

First posted sometime in early 2003:

 

I did my California tach two months ago and it is better than new for needle

stability. I found the same to be true for the 97 Sport when I did that

a few years ago. The problem with a lot of these tachs is that the case

mounting studs are the ground return path for the meter movement.

Although there are three wires going to the tach and one of them is a ground

lead, it is apparently only a ground lead for the electronics - not the meter

movement itself. What happens is the tachometer case mounting studs are

a press fit into the case with an interference mechanical fit. If they were welded

there wouldn't be a problem, but they tend to fracture the mechanical bond

after a while screwing up the meter operation. Not everyone has this

specific problem, sometimes the meter movement counterweights unglue

and fall into the bottom. Beyond the scope of my experience for that one.

 

It can be repaired though, and for not much money, but requires some patience

and if the tach is under warranty, I would push for replacement rather than

repairing it myself.

 

As for removing the tach to begin with? On the California, it's a bit of a nuisance.

For the 97 California, remove the headlight, the crosspiece between the

tach and speedometer and the other housing screw at the rear of the

tach as well as the rear cover of the instrument light cluster.

Inside the cluster is a screw into the tach housing. Remove that and

as I recall (I am going from memory here and I have certifiable CRS -

Can't Remember S?it) you can remove the tach and detach the wires.

Putting it back on is an amount of fun equal to or greater than the

original process. Be sure to have beer available to relieve the stress

but take care to not imbibe so much that the process becomes impossible.

The (somewhat) easy part is next. Lay the tach face down on a piece of

cardboard or an old dishtowel (go ahead, use a clean dish towel, just

don't expect me to explain it to your wife...) and using a very small

flat blade screwdriver, start prying the bezel lip upwards away from

the tach case that it is rolled over on. Just do a little bit, move a

few degrees around the case and do it again. A little bit of lift each

time. After you've gone around once or twice, you can use a bigger flat

blade screwdriver to pry the bezel lip to a nearly vertical position.

Once you can pull the bezel off of the tach housing, you remove the three

screws on the back of the tach housing and remove the guts. Set them aside.

Look into the housing and you'll see that the mounting studs are one of

those assembly line press fits. There is a very high probability that

either or both of them wiggle a tad (or if you have had too many beers

before tightening the tach onto the mounts, a stud has pulled completely

loose. One of mine was. I'm special, I don't need the beers as I am digitally dyslexic

and ambi-klutztrous). Any movement whatsoever is an indication that the

ground path is screwed up electrically and the stud needs to be re-secured.

Since very few of us have the skill or equipment to heliarc the damn

thing in place, only a really good epoxy will do. Use a metal loaded

one to help with electrical conductivity - something like JB Weld in the

USA and who knows what anywhere else. A dab on the outside of the case

and a large gob on the inside. Let it sit the full cure time - you don't

want to do this twice. Put the guts back in and with the bezel face

down on the towel, or yesterdays newspaper since your wife caught you

using her favorite towel with the little house and white picket fence

on it and you're now out in a cold garage with no beer because she took

that away too, and gently start bending the bezel lip back down around

the tach housing. A bit at a time and work your way around. At some

point it becomes possible to take a wooden stick or something similar

and a small hammer finish mashing the lip down tight to the tach case.

That's pretty much it, put the silly thing all back together (the

California's have some pretty berserk mounting hardware) on the bike

and take it for a ride. You should get a rock solid reading. In

accordance with Vaguelia specifications, all Moto Guzzi's are perpetual

motion machines. I can prove it. The tach always reads at least 500 rpm.

I didn't care to try and fix that.

[Guest ratchethack]

Thanks Al and Carl. Great stuff and well written too. Carl, yours was the write-up I had seen way back when. However, after going the "full Monty" route today (taking the guts out), I concluded that in my case, I probably didn't need to do this after all, because after careful inspection of the instrument movement, nothing appeared to be amiss. I wound up following essentially Al's less "invasive" technique and just wired in an additional known solid ground.

 

The press-fit of the studs evidently wasn't the source of the original problem, because both were still factory tight - that is, they were until I wiggled one loose, testing for tigtness I observed a "shoulder" on the stud, which was clearly preventing full & secure seating of the stud against the case. A poor design, to be sure. To solve this, I put on a washer just large enough to fit around the shoulder and stacked the smaller stock copper one on it, to provide good electrical contact. I believe this resulted in a far superior mechanical purchase than the stock set-up. Then I soldered my new good ground wire to the existing dubious stock ground solder lug from the harness (now redundant) on the case, and buttoned the whole mess up.

 

...But NOT BEFORE (MAN was I careful, I'm telling you!) breaking the stock instrument glass - AND ALSO breaking one of the extra custom glass replacements (Momma didn't raise no dummies) I had made for me (3 3/16" dia., 1/16" thick) at my local glass shop. Carl, after my second little do-si-do (and no beer in the fridge, either!) carefully, oh, so carefully - prying the bezel & replacing the glass, - well, let's just say by the end of the second time around I was finding your term "tedious" a bit of an understatement

 

Not taking anything away from your procedures at all, Carl & Al! Both were MUCH appreciated. So now I have a beautifully "refurbed" tach. Beautiful, I tell you, but the bezel isn't likely to survive another do-si-do with my elite swat team of knives and screwdrivers. She's all spent.

 

NOW, (are y'all ready?) the newly "refurbed" tach is every bit as dead as when I started! So any more thoughts on this, or is it starting to look like I might be due for placing an order for Vague - liar #2 at 18K miles?

[docc]

i've managed to dismantle and epoxy the mounting studs on the tach and speedo. Not a fun project. I'll post more on this in the 'grounding ' thread and try to create some links between some of these electrical threads.

 

It is notable that the JB Weld shows NO conductivity down to 0.1 Ohm. Fortunately my mounting stud still has connection to the case but be sure not to insulate the stud with the epoxy.

 

Thanks again to Carl for all the insight on where to look for this problem and also the magnificent wiring diagrams he has made available to all of us.

[moto pierre]

MY TACH PROBLEM After buying a 2000 V11 Sport as salvage, the first time I ran it the tach worked, but after much work including removing and replacing the front end, it no longer functioned. So I sent it of to Palo Alto Speedo and they reported that it was working fine. So I grounded the black center spade connector to the engine. Still no needle movement. I checked continuity from the ECU plug all the way to the instrument (black/yellow wire) and it was fine. When the engine is running I get voltage at both this wire and the red/black wire to ground. So how come nothing happens? I'm stumped. Yesterday I connected the ground wire to the mounting stud too, but I don't think it will help. I've heard that connecting the hot wire from one of the coils to the tach will also make it work. Has anyone done that? Getting to the connector on the coils is hell, and one of the three rubber coil mounts is already broken, so I'm reluctant to try removing either one for access to the connector. And which is the hot side anyway? Any ideas....

 

Moto Pierre

[mike wilson]

From all the posts I've seen on the reliability of instrumentations, I'd think there was a marketing opportunity for a direct-replacement-Jetsons-motor-scooter-LED-all-singing-all-dancing-type piece of kit.

 

http://www.motogadget.com/en/frameset.html

[callison]

MY TACH PROBLEM After buying a 2000 V11 Sport as salvage, the first time I ran it the tach worked, but after much work including removing and replacing the front end, it no longer functioned. So I sent it of to Palo Alto Speedo and they reported that it was working fine. So I grounded the black center spade connector to the engine. Still no needle movement. I checked continuity from the ECU plug all the way to the instrument (black/yellow wire) and it was fine. When the engine is running I get voltage at both this wire and the red/black wire to ground. So how come nothing happens? I'm stumped. Yesterday I connected the ground wire to the mounting stud too, but I don't think it will help. I've heard that connecting the hot wire from one of the coils to the tach will also make it work. Has anyone done that? Getting to the connector on the coils is hell, and one of the three rubber coil mounts is already broken, so I'm reluctant to try removing either one for access to the connector. And which is the hot side anyway? Any ideas....

 

Moto Pierre

 

This tach works on a pulse from the ECU. I believe that it will not work hooked across the coil, the older non-EFI bikes had tachs that worked that way. Cliff Jeffries provides a basic description at How My16M works.

[Guest Gary Cheek]

The secondary hairspring is a conductor. The hairspring breaks, the tach may go intermiitent for a while but it will quit. I have seen many of spring/conductors fail. Just gently move the needle while observing the hairsprings. Good chance you will find one has become disconnected near the attachment point. A repaired tach can be calibrated at a single point but will not track at other speeds due to the new spring rate.

 

I usually weld the goofy studs while inside the tach or speedo. Either a little brazing or TIG welding does the trick. I like to paint the salmon pink to white needle flat black too.

[kanoa]

how 'bout this one. i have a veglia tach replaced under warranty, it had been ordered by the PO when tach #1 died. since day 1, when tach #2 is wired up, it indicates RPM's flawlessly, fogs up only occasionally, and causes the turn-signal fuse to blow, religiously. could this also be a ground problem? or something upstream that fried tach #1? a few months ago i did a good amount of poking around with the multi-meter and head-scratching over carl's wiring diagram, but i honestly havent tried to tackle it since old man winter showed up.

[Guest oldtoolie]

My tach problems went away after I changed the relays.

 

You can see on the forum that the relays are the first thing to do when you have electrical problems.

 

oldtoolie in Hampshire

[callison]

My tach problems went away after I changed the relays.

 

You can see on the forum that the relays are the first thing to do when you have electrical problems.

 

oldtoolie in Hampshire

 

That's slightly strange unless other things also went away at the same time.

 

Still...

 

The tach on my Sport 1100i acted up at about 23,000 miles. Though the bike runs crappy right now (timing chain probably), it's not the relays. At 58,000 miles, the original relays are still in there. Apparently, the only thing you can say about Guzzi problems is that they're consistently inconsistent.

 

The only reason that I originally suspected the grounding studs was that the light in the tach wavered a bunch and the ground return for the light is definitely the case, regardless of how the internals of the tach work. Fixing the light fixed the tach as well. As I said, consistently inconsistent.

 

Don'tcha just love Guzzis?