2008 Breva 750 speedo dead

[hzbloke]

I'm getting about 4.5 volts at the connector under the seat, I presume I should be getting 12. I've had the connector to the instrument cluster out a few times and cleaned it with contact cleaner. Everything looks to be OK. The tacho and all of the lights work fine and the speedo does the sweep when I turn the key on. I replaced the speedo pick-up (at some expense) and that didn't help at all.

In the past the speedo has shown random (always low) speeds and has stopped completely before only to erratically work for a while. The last time it worked was after I had washed the bike. Some stray dash lights came on (including the mysterious red dot on the tacho) and the speedo worked until, I guess, the water dried out.

As far as I know there is only the one connector between the pick-up and the cluster and it checks out fine. Where have my extra volts gone and where should I be looking? Be gentle - I'm electrically challenged.

Cheers
Ray

[Moto]

You might like to look at this thread if you haven't already:

https://wildguzzi.com/forum/index.php?topic=43216.0

[Muzz]

The last time it worked was after I had washed the bike. Some stray dash lights came on (including the mysterious red dot on the tacho) and the speedo worked until, I guess, the water dried out.

Ray

Just a thought Ray.

During my shenanigans with a multitude of gearbox swaps, I forgot to connect the RH earth (mine is an '03 Breva but should be the same) up that bolts on to the bell housing up near the fins.

The dash went absolutely berserk. Found what I had done, bolted it up and it all went fine.

It may help to undo the bolt and clean up the contact.  The fact that it went a bit haywire after washing the bike makes me suspicious.

[hzbloke]

Thanks Moto. Yep, I've looked at that and I have continuity everywhere I should but only 4 or 5 volts where I should have 12. That thread (and the link it contains to another) sorta just fades away without a conclusion. As does Kiwi Roys dissection of a Breva/Nevada dash here: https://wildguzzi.com/forum/index.php?topic=76100.0

I also read through your efforts with a Griso (?) dash. You guys are playing in a league far, far removed from my bumbling abilities.

And thanks for that Muzz. I'll take that earth off (and the one on the other side) today and see what happens.

[hzbloke]

Removed, cleaned and replaced the two earths on the bell-housing. No change.

[Kiwi_Roy]

Here is a Breva schematic, hopefully like yours. Can you identify the connector you are referring too?
Yes, the dash should be getting 12 Volts.
Are the direction indicators working normally?
http://www.thisoldtractor.com/guzzi007/schematics/2004_750_Breva.gif

All the 4 fuses at (25) should have 12 Volts with the key On, two are fed through the switch.

[hzbloke]

My apologies. There are lots of connectors under there I should have been more specific. It is the 3 pin connector that joins the speed sensor (44) to the instrument panel (43).

The indicators are working correctly. In fact, apart from the speedo, everything is working very well.

I'm guessing you meant the fuses at 23 (25 is an indicator).

With the key on I'm getting: A 8v, B 13v, C 6.5v, D 9v

That doesn't seem right.

[sign216]

. The last time it worked was after I had washed the bike. Some stray dash lights came on (including the mysterious red dot on the tacho) and the speedo worked until, I guess, the water dried out.

I recall there's history of Breva speedos failing due to moisture.  I think on Guzzitech there's an old thread about fixing it.  I recall the repair was quite involved.

I checked Ebay, and there's some aftermarket speedos, economical, that claim to fit the Breva.

Let me know how you end up.
Joe

[Kiwi_Roy]

My apologies. There are lots of connectors under there I should have been more specific. It is the 3 pin connector that joins the speed sensor (44) to the instrument panel (43).

The indicators are working correctly. In fact, apart from the speedo, everything is working very well.

I'm guessing you meant the fuses at 23 (25 is an indicator).

With the key on I'm getting: A 8v, B 13v, C 6.5v, D 9v

That doesn't seem right.

Yes fuse-block (23) my eyes are not as good as they were
I suspect the odd fuse Voltages are caused by a bad ground on your meter, as you can see from the schematic A & B are wired together as are C & D, perhaps use a piece of wire under a handy bolt wrapped around the meter probe.  A & B could be low if the ignition switch was getting dirty (would show up as bad starting also)
A lower voltage on the connector to sensor might be normal +5 is quite common to sensors Red Black wire I think. It should be possible to connect an LED with resistor in series to one pin of sensor and chassis to see the pulses.
Check the gap from the sensor to the target at the rear wheel, I assume you haven't changed the bolts for stainless?

Can someone else with a small-block Breva comment.

Has your dash been wet recently?

[Chuck in Indiana]

^^^^ Whew! Those voltages made no sense to me so I didn't say anything. The ignition switch was one of my suspects.

[Kiwi_Roy]

Hzbloke
Does the speedo do its upscale dance when you turn the key on, or does it just sit at zero?

I have one that Pete kindly sent a couple of years back, I can fish it out to check on the Voltage at pin 2

[hzbloke]

A good earth makes a world of difference. Well deduced. Now I have 12.9v at each of the 4 fuses. I checked again and I have 9.3v at the 3 pin connector. But when I measure across pins 2&3 and turn the back wheel I get readings of 2 to 5 millivolt, not the .5 to 12 volts expected.

Yes, the needle does do its dance when the key is turned on. And the bike starts easily every time.

"connect an LED with resistor in series" I am familiar with the concept discussed here (make light flash) but you overestimate my electrical ability by a factor of many.

The sensor is 1.5mm from the bolts. They are, as far as I know, original and a magnet sticks to them. The bike has not been wet recently.

Thanks Joe. I went looking for the Guzzitech article but didn't find it. I had a look at those aftermarket speedos. Some are incredibly cheap but I presume all would require messing with existing connectors etc. See previous comment on electrical ability.

As the rest of the dash works perfectly (except for the odometer and trip meter) I've been using a bicycle speedo. $35, no wiring. Far from ideal but helps avoid speeding tickets.

[Kiwi_Roy]

I measured my 2007 Griso and here's what I got.

I could poke the meter probes into the rear of the connector socket (loom side)
From the centre pin to chassis it changes from 10.6 Volts DC without a target dropping to about 0.344 DC when the target is in place

I suspect the sensor is probably a Hall Effect Switch with a weak magnet to turn the switch to one state and the field is diverted so it changes state when a ferrous target is introduced
Whatever it is it will have a nice square wave output.
I have to assume the Griso and Breva use the same sensor.
Its also essential to seal where the cable exits the sensor with silicone as they will wick in water and short out or corrode otherwise. The hard epoxy and soft cable makes for a perfect leak point.

It might be possible to roll your own sensor using a reed switch and magnet/s

UPDATE
These magnet biased sensors have a very short sensing range, typically only a couple of mm, could that be the problem?

From a V7 manual, I suspect all the Guzzis use the 883768 magnet biased Hall Effect sensor

[hzbloke]

Still not fixed but Kiwi Roy has been doing excellent work in the background (despite also having fun touring NZ) looking for a solution.

I've checked my old and my new sensor and they both put out millivolts when they should show .6 to 12 volts when the sensor is triggered. Not sure exactly why this is but could two sensors fail in exactly the same way?

Some good information from an Aprilia forum here: http://apriliarsv.com/guides/16285-inexpensive-speedo-sensor-fix.html

More news as it comes to hand.

[Kiwi_Roy]

Yes, two sensors could fail the same. The usual failure is caused by moisture wicking into the crack between cable and the body, this shorts out the sensor connections.
I learnt the hard way with industrial pH probes costing over $500 how vulnerable these potted sensors are to moisture ingress, it's bad design.
Have you tried drying out the two you have, overnight in a warm oven might get one to work.

If your sensor has steady power across 1 & 3 and the output is not toggling between 1 & 3 I suggest it's shorted out holding the signal low

Using my Griso as the test rabbit.
The output of pin 2 switches between +10.3 and +0.3 reference to battery negative (chassis)
I found that putting a jumper momentarily into the socket between 2 & 3 causes the speedo to go to 300 for a second and it's possible to get it to read other values with a momentary contact, this proves to me that the speedo is working.

Thats a very good link you posted, I quote;
The original sensor is a biased hall effect device, i.e. a hall effect sensor combined with a permanent magnet. The output is a an open collector, i.e. the signal wire is grounded when ferrous metal is in front of the sensor, and is floating when no metal is present. The instrument pack pulls this wire up to around 9-10 volts, giving a 0-10volt swing. My sensor was still working to some extent, but the voltage swing was from 0volt to less than 1 volt (too low for the instrument pack to register) which indicates a high leakage current (probably moisture ingress).

I know the sensors are expensive but peanuts compared to a new dash, using a different type requires you to make a new bracket.
When you get a new sensor waterproof it before use with some silicone sealant around the cable entry.

[hzbloke]

I managed to remove the actual sensor from its housing. It is a Honeywell 1GP7001 Geartooth Sensor. After soldering the wires on it is embedded into the hard plastic casing in what I guess is an injection molded firm rubbery material. It's a bugger to get out. For the record: the Moto Guzzi part number is AP8124528.

[Kiwi_Roy]

This is great information Hzbloke is providing,
Guzzi part AP8124528 the Honeywell chip is less than $50 at Digikey part No 48-02826-5-ND

This is not the same sensor as used in the flat package 883768 used on CARC bikes

Actually I think in Hzbloke's case the chip is not drawing enough current to pull the Output up when it turns Off
I suggested he adds another resistor between Positive and Output (1 to 2 at the plug 1 to 3 at the sensor).
The chip is capable of sinking 40 milliamps, I picked a conservative 10 milliamps which would call for 1,000 Ohms

The good thing is it's very easy to test by measuring at the 3 pin connector
Pins 1-3 (power to chip) should measure approx. 12 Volts
Pins 2-3 (output) should measure 0.4 - 12 Volts as the target moves past, turning rear wheel slowly.
 
Note the sensor needs to be set about 2 mm from target.

[Muzz]

After reading all this Roy I am pleased my speedo works.

[hzbloke]

I've put washers under the bolts on the rear disc to reduce the gap between them and the sensor casing. It was previously 1.5mm. But the hard plastic casing in which the actual sensor is embedded is about 1.5mm thick and so the actual sensor was really about 3mm from the bolt head. The spec sheets says its operating range is 2.28mm. The speedo still doesn't work.

But I did put a 1000ohm resistor across pins 1 & 2 as Kiwi_Roy suggested and I now get an LED (with 10k resistor) from pin 2 to earth to light (it's off when a bolt passes and on inbetween bolts, is that right?). But the speedo still doesn't work.

I took the speedo instruments off and checked the connector. All three wires for the sensor are fine and have continuity back to the connector under the seat. But the speedo...etc etc

[Kiwi_Roy]

It's good you now have the sensor switching however it may be that the LED you have between 2 and 3 is the problem, if its just a bare LED with no series resistor it will clamp the input at the Forward Bias Voltage, too low for the speedo to see as a change of state.
Check the Voltage on pin 2 with and without the target then take the LED off and see what pin 2 does then note down the two levels and report back.

I'm just guessing the speedo input switches at around 5 Volts I would like to see it go to about 8.
I can check this over the weekend.

If the Voltage on pin 2 is still low you might try adding another 1K resistor in parallel thus doubling the Pull-up current.

Good Luck

[hzbloke]

I've tried both of the options Kiwi_Roy has suggested (see diagrams) and am getting .28v and 8.2v on pin 2. Still no movement on the speedo. A second 1000ohm resistor across 1 & 2 has had no effect.

I may not have got the speedo to work yet but I have got an LED to blink and that, for me, is quite an achievement. Thanks Roy.

[Kiwi_Roy]

Oh dear - You certainly gave it your best shot came from no switching at all to getting a good pulse and we have learnt a lot about the sensor along the way.
Hang in there and I will do some poking around in case I have missed something obvious.

[hzbloke]

Still not a working speedo but Kiwi_Roy has been doing great work trying to come up with a reason why. His diagram (below) of the plug at the back of the instrument cluster is the clearest I have seen yet and makes testing much easier. Thanks again Roy.

[sign216]

Still not a working speedo but Kiwi_Roy has been doing great work trying to come up with a reason why. His diagram (below) of the plug at the back of the instrument cluster is the clearest I have seen yet and makes testing much easier. Thanks again Roy.

Kiwi,
The diagram is marked "Breva 850."  Does it apply to the Breva 750?  The 850 is a big block, and the 750 small block, and in other matters they can be very different.
Joe

[Kiwi_Roy]

Kiwi,
The diagram is marked "Breva 850."  Does it apply to the Breva 750?  The 850 is a big block, and the 750 small block, and in other matters they can be very different.
Joe

Joe,
       That's my mistake, I have a 750 dash that Pete sent me and it's based on Carl's schematic of the 2004 750 Breva.
I just assumed the 1100 was the big block.
Thanks for catching that.

[sign216]

Joe,
       That's my mistake, I have a 750 dash that Pete sent me and it's based on Carl's schematic of the 2004 750 Breva.
I just assumed the 1100 was the big block.
Thanks for catching that.

Okay, thanks.  Just checking on that detail. 

The 750 is the biggest smallblock Guzzi's ever made, and ironically, that's the size of the original big block.

[F-22]

Okay, thanks.  Just checking on that detail. 

The 750 is the biggest smallblock Guzzi's ever made, and ironically, that's the size of the original big block.

No, the very first Guzzi twin was 700cc. Then came the ~760cc V7 Special/Ambassador, and then the 850GT/Eldorado (700 had a smaller bore, 760 had standard 83mm bore and shorter stroke than the final 850 model). I think the only real 750 they made back then was the V7 Sport model since 1971 (later the twin and triple disc versions of the same bike - the 750 Sport and S3), they used a smaller 82,5mm bore, so that they could also use these bikes for 750cc racing. However, I think the V7 700 was sold/manufactured for longer than the other two "upgraded" loop frame models (they were made specifically for Italian police/military use up to the mid 70's, the Eldorad was replaced with the T3 a little sooner).

[hzbloke]

I haven't given up on getting my speedo working, I've just been away for a few weeks (Darwin, Kakadu - recommend it). This arrived while I was away:



It came from here: https://www.ebay.com.au/itm/1-5mm-Inductive-Proximity-Sensor-Switch-NPN-NO-DC-6-36V-100mA-3-wire-PR08-1-5DN/303101996626?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20190212102350%26meid%3De8a627e705c34cbab50b0a9d5115d2a8%26pid%3D100012%26rk%3D3%26rkt%3D12%26sd%3D302730027116%26itm%3D303101996626&_trksid=p2047675.c100012.m1985

And this is the tag attached to it:




Although it is looking increasingly like the problem is in the instrument not the sender I will test it to be sure.

Could someone (hi Kiwi_Roy) please confirm how to connect it to the existing wiring?

[Kiwi_Roy]

There is a data sheet on this site
https://octopart.com/pr08-1.5dn-autonics-12800363

Unfortunately I have a very short attention span and I retired so I no longer have access to my notes.
Brown +
Black Switch  This wire should switch between Negative and Positive I think, I'm not sure if you need Pull Up or Pull Down resistor
Blue -

Perhaps try it first with the black wire off to see what it does

Good Luck

[hzbloke]

No joy I'm afraid. With nothing to lose I tried every combination of wire, with and without a resistor - nothing.

I'm about to head off riding for a week (yeah, life's pretty good). When I get back I'll pull the instruments off again to recheck that everything in the connector is OK.

After that: I quite like the look of the new V7 III Special.

Thanks again Kiwi_Roy for all your help.