2004 Breva 750 Speedo Sensor Replacement

[Figly]

Howdy!  Quick question regarding the proper procedure for removing/replacing the speedo sensor on a 2004 Breva 750.
I've heard it's pretty simple, but I just want to make sure I'm doing it properly beforehand so I don't screw anything up or make more work for myself, which seems to be a pretty common theme with me haha!

Already found (and removed) the one bolt that holds the sensor itself onto the bike, and from here it looks like you just disconnect the connector underneath the seat, then pull the cable down through (pulling the cable down toward the rear wheel), and pull the sensor out toward the center of the wheel (right side of the bike) with the cable following it through its hole.

If anyone has had experience replacing this part please let me know, I'd definitely appreciate any advice!

(Originally piggybacked on this thread, without any replies so far, but that's where I found some great diagnostics and helped me pinpoint the problem: http://wildguzzi.com/forum/index.php?topic=43216.0)

Thanks in advance!

[Kiwi_Roy]

 If the gap is adjustable set it close enough to trigger the sensor and a bit closer for luck.
Would you mind taking a picture when you get it mounted.

From the other thread I got 6 pulses per revolution, I would like to figure out how many per mile/kilometer, I have a unit Pete sent me, I am trying to make up a test rig.

[not-fishing]

If the sensor is anything like the Griso and I bet it is, don't forget to add a little dab of silicon caulk to where the wire just goes into the sensor.

It's a water opening for wheel back-splash.

[Kiwi_Roy]

If the sensor is anything like the Griso and I bet it is, don't forget to add a little dab of silicon caulk to where the wire just goes into the sensor.

It's a water opening for wheel back-splash.

That's a very good idea, where flexible wires come out of a rigid epoxy housing is a natural place for the water to wick in between wire and epoxy to short out or corrode the electrical jonts, chances are that's why the original failed a Hall effect should last forever.
The silicone will flex across the gap, it works very well as a seal for electrical equipment.

[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 ran the checklist below (excerpt from the service manual), and as far as I could tell everything above the sensor was good (good voltage, good continuity, etc.):

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 in the other thread mentioned that "The speedometers can be unreliable, aren't repairable, and can be expensive".

P.S. - I did silicon around that housing, even though the new sensor looked 100% better constructed than the old one, and I do have photos of the process/location that I'll post eventually (probably after I get it completely solved).

[Kiwi_Roy]

What is the gap between sensor and the bolts it should be quite close.
Is the sensor magnetic, attracts a screwdriver.

It should put out a pulse each time a bolt passes.

You haven't changed the bolts for stainless ones have you? They must be ferrous, stainless isn't.


You said
Pin-out:
PIN:
· PINS 1-3 Voltage: approximately 12 V
· PINS 2-3 Voltage: between 0.6V-12V (turning the rear wheel) They mean it should alternate from 0.6 to 12 as the bolt heads pass
 

[Figly]

That was me posting on the other thread also - I'll keep everything here from now on, but post the solution over there (once we find it) for more visibility.

Yes the gap is very small, the sensor is probably only a couple of mm from the bolt heads (it's not adjustable, and the replacement sensor appears to be identical size to the old sensor).
I don't believe the bolts have ever been replaced, and I know for a fact they haven't been changed since well before I started having issues with the speedometer, if ever. I gave the bolt heads a good scrub with a wirebrush to get them nice and clean, but there didn't seem to be much gunk/rust or anything on them to begin with.

When holding a small screwdriver up to the sensor, it does feel like it's magnetic.

Thank you for the clarification on the service manual's Pin 2-3 voltage description - that was pretty much how I interpreted it (that it should pulse or vary in voltage when the bolt heads passed), but I wasn't 100% sure so I appreciate your description.

Here's what I found out after going through that diagnostic checklist again with my multimeter:
The Pin 1-3 voltage is only about 9.3V, not sure if that's a significant enough drop from the 12V to cause an issue?
The Pin 2-3 voltage when turning the rear wheel DOES pulse, but it is a VERY small variance (0.1-0.2V normally, then it drops to ~0.04V when the bolt heads pass over the sensor). My guess is that it's not being recognized since the normal P2-3 reading is too low to begin with (maybe due to the lower voltage coming in from the supply wire?).
The continuity between Pin 13 on the instrument panel and Pin 3 on the sensor connector as well as between Pin 17 on the instrument panel and Pin 2 of the sensor are both showing good continuity though, so not sure where the drop is occurring...also checked continuity between Pin 1 (I think) of the instrument panel and Pin 1 of the sensor connector, and they also have good continuity. All resistances between these pairs are showing as ~0.3 ohm.

Thoughts?

Thanks again for the help!

[Kiwi_Roy]

Here's what I found out after going through that diagnostic checklist again with my multimeter:
The Pin 1-3 voltage is only about 9.3V, not sure if that's a significant enough drop from the 12V to cause an issue?
The Pin 2-3 voltage when turning the rear wheel DOES pulse, but it is a VERY small variance (0.1-0.2V normally, then it drops to ~0.04V when the bolt heads pass over the sensor). My guess is that it's not being recognized since the normal P2-3 reading is too low to begin with (maybe due to the lower voltage coming in from the supply wire?).
 

I think the + 9.3 is probably ok but I'm surprised the 2-3 Voltage is so low it should vary from about 9 to .6 or thereabouts as the switch changes state.
With the sensor unplugged what is the Voltage between wire 2-3?

With the cable unplugged at both ends make sure it's an open circuit between any two wires, reverse the meter leads and do the test again. The meter should read open circuit instantly, if you see a slow change get back.

[Figly]

There does not appear to be any voltage between pins 2-3 with the sensor unplugged (either on the sensor side or the instrument panel side of the connector).

After unplugging the cable at both ends (I assume you meant unplug the connector under the seat as well as the instrument panel connector from the instrument panel), when using the continuity test mode, all pairs of wires were open circuits (no continuity found), but when I switched to resistance mode, I was reading 6.89M ohms between Pins 2-3 on the instrument panel side and 5.8M ohms between Pins 2-3 on the sensor side.

[Figly]

Update - I was out riding it yesterday and the speedometer started working again...very intermittently, but there it would be working perfectly for a couple minutes at a time, then not at all, and then sometimes it would be on and off working for a few seconds at a time...SO WEIRD!

[Kiwi_Roy]

It's difficult to find an intermittent some times, what I think it's not is the dash itself.
Inspect all the connections again.
Do you have a centerstand it might be possible to wiggle the connectors while the bike is running, another idea would be to wave a target in front of the sensor with a drill or something.


Sent from my shoe phone!

[jjanhunen]

Update - I was out riding it yesterday and the speedometer started working again...very intermittently, but there it would be working perfectly for a couple minutes at a time, then not at all, and then sometimes it would be on and off working for a few seconds at a time...SO WEIRD!

Hey,

Did you ever found reason for that failure? I have a 2003 Breva, and there has been exactly same behaviour with my bikes's speedo. Before I red this topic, I changed speed sensor, but it didn't help. Usually speedo have just worked or not, but yesterday it began to show all kind of readings until went all dead..

I have checked all connections, and they seems to be ok.

Local dealer said, that some Italian bikes have had some corrosion in PCB inside dash panel/cluster. I opened it, and there were little bit corrosion, especially around that big connector. So, I cleaned whole PCB with proper cleaner, and will see is it going to help.

This "feature" have not bothered me, because usually I do all my riding with Tenni Griso. But now I'm probably going to sell (try..at least) that Breva, so it would be nice if speedometer would be in working condition..

Greetings,

Jani

[Kiwi_Roy]

The Hall Effect transistor should pull wire 2 up from zero to nearly the Voltage on wire 1, I'm wondering if you don't have a high resistance joint in one of the connectors so the transistor is not seeing the full Voltage.
Is it possible to read the Voltage with the connectors plugged in?
Perhaps strip the insulation back where the cable runs through a dry location and probe the wires with sewing pins.
Or can you measure it at the plug under the seat with it partially unplugged?

You were reading 9.3 Volts earlier, I suspect this was with the sensor disconnected, the multimeter only draws a few microamps a fraction of what the sensor draws.

Pete Roper kindly sent me a dash off a 750 Breva, I will try to get some readings off it.