Relay question

[Eliminator]

I've read so much about relays recently, watched videos, my head is spinning. Trying to trace an intermittent electrical fault for an amateur numpty like myself isn't easy. I'm "learning" as I go. All I can do, is report what I find. Must be frustrating as a professional, reading about my haphazard approach and thoughts.
My simplistic thoughts on the difference in the engine when I swapped the relays, is this. If there is an intermittent fault in either the relay or associated wiring, that causes the rev counter to fluctuate, might it be the case that the engine could be slightly misfiring at the same time? When I swapped the relays,(or maybe nudged a loose contact) the rev counter did not bounce, so the engine would seem to be running stronger.

 

[scottmastrocinque]

“Possible and probable are usually a million miles apart from each other”. - Unknown

I mean no pejorative.

Only if you understand that a relay used in a motorcycle, is just a glorified switch, that has only 2 position, OFF and ON, then you begin to see the situation.

I have to go back and carefully analyze what you have written again and look at the wiring diagram. e.g. where there is a relay in the path of the tachometer, if at all.

I will ponder on this more and see if I think of anything to help further.

 

[Eliminator]

To save you reading through all of my waffling, and my assumptions, these are the basics.

Rev counter started fluctuating for a week or so.

Then the bike stalled a couple of times a few hundred yards after starting, when I stopped at traffic lights.

Engine reluctant to start, started then ok for the 25 miles going home.

Happened again one evening, but stalled twice. On the way home, the rev counter reading about 6,000rpm, when I knew it was far lower.

Seems that the rev counter takes a signal from the Digiplex on the wiring schematic, I can't see a relay relating to the rev counter.

 

[scottmastrocinque]

…Seems that the rev counter takes a signal from the Digiplex on the wiring schematic, I can't see a relay relating to the rev counter.

This makes perfect sense to me as I am 99% sure there isn’t a relay between the battery and the tachometers.

I think you are experiencing a coincidence of non related events.

I have experienced the same jumping, erratic tachometer on every Moto Guzzi motorcycle I have owned from that period.

(California III, California 1100i, California V-11 EV, V-10 Centauro x 2, and my current California Vintage).

The internals on the tachometers are all very delicate and not the most robust construction.

If you look at virtually any V11-EV, V-10 Centauro, or 1100 Sport, they all look like the ones below with the tachometer no longer reading ZERO correctly.

It’s usually not far down the road from this symptom that the erratic jumping of the needle begins appearing.

I wrote a post about Joel Levine, (Available under SEARCH) the gentleman I send mine to for upgrade and repair. Many others have said the same thing too.

I am much more inclined to believe that your tachometer is failing internally but your random cutting out and running issue are related to an intermittent break in a wire in the main loom, or that the crimping on a main fuse is loose or shorting out randomly. When you go pressing on stuff, you are moving things that is moving wiring.

Your symptoms just aren’t attributable to a relay and how it functions.

They are either working as a switch or they don’t work. (On or off)

These types of issues are the hardest to track down.

 

[GerryAZ]

The relay reference information Scott posted is great--I printed it for future use. Other terminology you will see regarding relay contacts are Form A, Form B, and Form C contacts. Form A contacts close when the relay coil is energized (normally open contacts); Form B contacts open when the relay coil is energized (normally closed contacts); Form C contacts have three terminals with a common terminal that is connected to one terminal when the coil is energized and the other terminal when the coil is not energized (changeover contacts in Scott's reference).

It happens rarely, but I have actually had a couple of intermittent failures of these small automotive relays. The springs can get weak and loose connections in the coil circuit (or high resistance wiring) can cause inadequate contact pressure so the contacts bounce between open and closed.

 

[Eliminator]

Thank you for giving your time to help. The quest goes on.

My rev counter has sat on 500rpm since I bought it in 2012.

 

[Eliminator]

I've ran the bike for about 15 miles every day since my last post. I bought a can of contact cleaner, sprayed all the relay bases, and pins on the relays. Sprayed the fuse box, I did notice that I had failed to push one fuse fully home, I wonder if that's why one of them overheated before?

Anyway, no more bouncing rev counter, not engine stalling or stumbling.

Just hope I haven't tempted fate

 

[scottmastrocinque]

Did you also remove and clean your ground strap for the negative battery post to the engine? If not, do this as well. You want a good clean circuit from + to -.

 

[Eliminator]

I'll do that.