Breva 750 Speedo intermittent now not working, any ideas?

[pentrich1]

My 2006 Breva 750 developed an intermittent speedometer a few weeks ago, and it would jump around all over the place whilst riding.  now it has stopped and is constantly on 0 mph.  It does however spin around on ignition with the rev counter (as it should) and then settle back on 0 mph as normal.

It has rained a lot lately which may be a cause, but i'm hoping it is unlikely to be the rather expensive clocks that are faulty. 

Does anyone have any knowledge on this?

I will take a look at the sensor on the back wheel soon.  I noticed though that some bikes have a magnet on the disc that triggers the sensor each time it spins, but mine does not seem to have one?

Any help would be much appreciated.

Regards

Travis

[sign216]

Travis,
The speedometers can be unreliable, aren't repairable, and can be expensive.  Before buying a new unit, here are some things to check;

- Corrosion at the multi-connector in back of the "dashboard."  Take off the connection, inspect, and spray w electrical contact cleaner.  Not WD-40, but a real switch cleaner.  The cheaper ones are just alcohol in a can, but there are some good brands that will fight the corrosion.  The brand names escape me right now.  Anyone remember a good brand?

- Examine the inductive speed sensor at the rear brake caliper.  Sometimes they get engine oil on them, or crack, or it may have loosened.

Let us know what you find out.

Joe

[flashman]

Travis,

Based on your description, I'd be leaning towards something outside the instrument cluster being the culprit.  Logically, there can only be three places the problem lies; the instrument cluster, the wiring harness between cluster and sensor, and the sensor itself. 

If your dash passes the built in test (needle sweep), then it should not be the cause...  The manner of failing you describe sounds a lot like an electrical contact problem, given that it started intermittently and got worse.  Since the wiring harness is fairly well protected, I'd start looking at the sensor first as Joe says.  Check the sensor for condition or damage, then check the molex connector where it plugs into the wiring harness.  The good news is that if it is the sensor, they're not very expensive - about $75 - and are a common Aprilia part (AP8124528)

PS - the disclaimer here is that I have just about enough knowledge to be dangerous, but the above is what I would do were it my bike.

PPS - Just for fun, I'm going to venture a prediction - loose or corroded connection from sensor to main harness.   

[iamz]

"- Corrosion at the multi-connector in back of the "dashboard."  Take off the connection, inspect, and spray w electrical contact cleaner.  Not WD-40, but a real switch cleaner.  The cheaper ones are just alcohol in a can, but there are some good brands that will fight the corrosion.  The brand names escape me right now.  Anyone remember a good brand?"

For cleaning the contacts, try finding some CRC 2-26.

[windsurfed]

Since the speedo sweep works, and the speedometer reads 0 when you are riding, I think you will find it in the magnetic pickup in the rear tire area.  Sounds like you may have lost one of the the magnets.

[Chuck in Indiana]

but there are some good brands that will fight the corrosion.  The brand names escape me right now.  Anyone remember a good brand?

Dr. Wayne recommends Caig Dexoit. Good stuff, I might add.

[pentrich1]

Thanks for the replies so far, I had a look at the sensor and it appears okay.  I'm in agreement that it is most likely away from the speedo unit as it seems to function perfectly otherwise.

I am however finding it hard to find out if the breva uses a magnet mounted on the rear disc to trigger the sensor.  Web searching brings up nothing.  My bike doesn't have a magnet, so either it has fallen off or it is supposed to be like that?  Does anyone have a breva 750 that they can have a look at to see if it should?

Any help appreciated

Thanks

[NOLAGuzzi]

The manual for the small block breva says it is a hall sensor with six pulse/revolution square wave output.  No specs for testing the function of the sensor are given though.  The parts and service manuals can be found on the guzzitech website if you need them.

I looked at my breva and it seems to me that the pulse(s) are triggered when the each of the six brake disc mounting bolts pass in front of the sealed sensor.  My speedo works and I don't see any magnets anywhere on mine.

I'd check/clean the connections well and/or find a dealer or person with the computer diagnostic tools to test the sensor OR look for a used (cheap) sensor on ebay and just swap the part. 

[pentrich1]

Thanks for that info, I am going to try and find a sensor online to swap.  I had a good look at mine today and it looks fine, maybe a small knick in the rubber. 

Now to find a sensor....why are they so expensive!

Cheers

Travis

[flashman]

Travis -

I guess this is why there's the expression "RTFM!"  Just checked the V7C workshop manual and found this...  I guess I should have looked there first  ::)

Speed sensor.

Function:  To indicate the vehicle speed by reading the rear wheel rotation speed.

Operation / Operating principle:
Hall effect sensor: a square-wave pulse is generated with voltage between 12V and approximately 0.6 V.

Level in wiring diagram: Speed sensor

Location:
· Sensor: on the swingarm, left side, next to the rear brake calliper.
· connector: under right fairing, next to the Marelli control unit.

Pin-out:
PIN:
· PINS 1-3 Voltage: approximately 12 V
· PINS 2-3 Voltage: between 0.6V-12V (turning the rear wheel)

1. Supply voltage (green - sensor side)
2. Output signal (grey/white - sensor side)
3. Ground (blue/orange - sensor side)

DIAGNOSIS.

Speed viewing problems on the instrument panel: 
CARRY OUT THE CASCADE OPERATIONS UNTIL THE FAILURE IS FOUND

- Check correct position of the sensor in its fitting.
- Check voltage between PINS 1-3 of the sensor. If there is no voltage, check continuity between PIN 1 of the sensor and PIN 3 of the instrument panel connector.
- Check the instrument panel PIN 13 connector.
- Check continuity with the sensor PIN 13 ground lead.
- Check continuity of the grey/white cable harness (cable harness side) from PIN 2 of the sensor to PIN 17 of the instrument panel connector.
- Check instrument panel PIN 17. If there is no failure after all these checks, replace the sensor.

[pentrich1]

Thanks for the above diagnostic tests, much appreciated!  I did the tests and all seems well with the system above the sensor.  I have ordered a new sensor so fingers crossed that sorts it out!

As I have looked really far into this issue I thought i would summarize my findings for future help.  It turns out that the Aprilia guys have had no end of troubles with these sensors on various models.  At current there seems to be no pirate/copy part so the only option is to replace with a AP8124528 Aprilia OEM sensor.

These are known as 'hall sensors' and each time the disc rotor bolts (which need to be steel ones so aftermarkets may disrupt the readings!) pass the sensor, there is a small drop in voltage which is recorded by the clocks and the frequency of the passing bolts is turned into the speed reading on the clocks.  Thus there is no magnet, but rather the passing bolt upsets the magnetic field of the sensor and causes the needed drop in voltage.

Another common cause on other models seems to be either a snag of the cable in the swingarm causing damage to the wires, or the bending of the wires when disconnecting the rear brake calliper carrier and letting it hang (thus exceeding the safe bend radius of the cable).  So a tip would be to make sure the cable is clear of any snags on its way from the rear wheel to the connector under the seat area, and perhaps tying up the calliper carrier when removing the rear wheel to prevent it being over stressed.

Once my new sensor arrives I shall report back!

thanks again for all the help

travis

[sign216]

Travis, great work.  Good to know these details.  I'm surprised there's not a sensor from another brand that fits.  Perhaps it just hasn't been found yet. 

[pentrich1]

Update:  I fitted the new sensor and just like that - it works perfectly again!  I noticed the new one is slightly different in that where the cable goes into the sensor head, it is a sealed unit, where as before there was a small rubber boot that could be slid back, maybe a solution to water ingress?

[Figly]

Any hints on how to remove/replace this sensor? I had the same symptoms and diagnosis as you (thanks a million for that manual excerpt, was a lifesaver!), and have a new sensor on its way, but was wondering what's the best way to get the old one out and new one in?

I found the single bolt holding the old sensor in and removed that - after that, is it just a matter of pulling the cable and connector down through the body and running it all out through the hole the sensor sits in (toward the wheel), or is there a different solution that I'm missing?

Thanks in advance!

[Figly]

Update: apparently my original diagnosis was wrong...popped the new sensor in today and still no reading on the speedometer. Unless I jacked up the new sensor putting it in, looks like my problem might lie elsewhere.

I did run the checklist (which is what lead me to believe it was the sensor), and as far as I could tell everything above the sensor was good (good voltage, good continuity, etc.):

Quote
Speed sensor.

Function:  To indicate the vehicle speed by reading the rear wheel rotation speed.

Operation / Operating principle:
Hall effect sensor: a square-wave pulse is generated with voltage between 12V and approximately 0.6 V.

Level in wiring diagram: Speed sensor

Location:
· Sensor: on the swingarm, left side, next to the rear brake calliper.
· connector: under right fairing, next to the Marelli control unit.

Pin-out:
PIN:
· PINS 1-3 Voltage: approximately 12 V
· PINS 2-3 Voltage: between 0.6V-12V (turning the rear wheel)

1. Supply voltage (green - sensor side)
2. Output signal (grey/white - sensor side)
3. Ground (blue/orange - sensor side)

DIAGNOSIS.

Speed viewing problems on the instrument panel: 
CARRY OUT THE CASCADE OPERATIONS UNTIL THE FAILURE IS FOUND

- Check correct position of the sensor in its fitting.
- Check voltage between PINS 1-3 of the sensor. If there is no voltage, check continuity between PIN 1 of the sensor and PIN 3 of the instrument panel connector.
- Check the instrument panel PIN 13 connector.
- Check continuity with the sensor PIN 13 ground lead.
- Check continuity of the grey/white cable harness (cable harness side) from PIN 2 of the sensor to PIN 17 of the instrument panel connector.
- Check instrument panel PIN 17. If there is no failure after all these checks, replace the sensor.

In addition to the checklist above, I've also checked the multi-connector in the back of the instrument cluster (all pins appear intact and relatively clean, definitely corrosion-free), sprayed it down with electrical contact cleaner, and wire-brushed the pins as best I could.

Any ideas at this point? I'm hoping it's not the cluster/speedometer itself (passes the sweep test when the key is turned on), as someone mentioned earlier, "The speedometers can be unreliable, aren't repairable, and can be expensive".

P.S. - I do have photos of the process/location that I'll post eventually (probably after I get it completely solved).

[Kiwi_Roy]

There's another thread on here, same issue


http://wildguzzi.com/forum/index.php?topic=76302.0

If you think it might be moisture try warming it up in an oven it may drive the moisture out then seal it with silicone

I think the sensor must incorporate a magnet, test it with a screwdriver. it picks up on bolt heads passing which will cause the internal magnetic field to distort and operate the Hall effect switch.
Would you mind taking a picture of the sensor in-situ and the connector. If you have a 12 Volt LED it should be possible to wire it between 2 & 3
to turn on as the bolt heads pass.
When I get time I hope to figure out how to test the unit Pete sent me.