Technical Fiat Barchetta Speed Sensor problems

[peace4uno]

Hi!
Is there a way of finding out if the sensor VSS, is working or not. Cables or sensor.

I have checked the service manual, and found the wiring drawings. I think I have found the right point on the speedometer connector to measure the Hall effect. In my understanding, I should be able to measure it with a multimeter, Volt. That is the idea, I expected 5-10 volt, down to 0. And this would indicate that the sensor is working. I have opened the speedometer, tried to look over all connection points/soldering.

So my question are, how can I check if the sensor is working.
Where should i measure it?

Any OEM number on the sensor. Barchetta 97

Any other sensor that is connected to this, wheel, abs?

 

[wapper]

Here's an old post that could help with diagnostics https://www.fiatforum.com/threads/speedo-and-odometer-not-functioning.331243/

Usually the instrument cluster is the component to blame, not speed sensor. Those bad soldering points are hard to detects. It's probably better to resolder everything. I walked that path when I bought my B, changed speed sensor with no positive effect, then checked all joints with magnifying glass, with little bending of the circuit board. Found nothing, my speedometer still sometimes doesn't work but wakes up after a friendly slap on top of the instrument cluster.

 

[peace4uno]

Here's an old post that could help with diagnostics https://www.fiatforum.com/threads/speedo-and-odometer-not-functioning.331243/

Usually the instrument cluster is the component to blame, not speed sensor. Those bad soldering points are hard to detects. It's probably better to resolder everything. I walked that path when I bought my B, changed speed sensor with no positive effect, then checked all joints with magnifying glass, with little bending of the circuit board. Found nothing, my speedometer still sometimes doesn't work but wakes up after a friendly slap on top of the instrument cluster.

Hi!
Thank you for the response. I did take the speedometer to an old tv/radio guy, who checked over the soldering. Could not see anything wrong on the solderings. I also tried to put some voltage and MilliAmps straight on the pins on the speedneedle, circuitboard pins that is. This made the needle move, more milliamps made the needle go higher. This means that some parts are working.

The sensor I removed looked like picture 1.
The sensor was replaced by this: Picture 2.

My Car Vin number is: 24893
Model 97

I´m guessing that the sensor I need is:46403099


At the same time, what is the difference? Could this work on mine? 46817374? I used AutoDoc to get the speed sensor part 46817374.

When I tried the new part, it would give me a voltage between 0-8 volt. That would give me a puls, but not sure what is the correct one. Then I tought it might just be the sensor type that is not working correct, or giving the right type of signal.


I´m lost in space, since I´m not able to get any verification of what is the correct signal out of the speedometer sensor. That I could measure with voltmeter.

If I must use 46403099, where can I get it? Not a easy part to find online.

Any tip or help?

 

[Wiltshire Chris]

Not sure I can be a lot of help but here goes

Henk stocks a few speed sensors so may have the right one for your model, I agree that it is likely to be 46403099

Mechanical Parts – Page 16 – Barchetta Parts

barchettaparts.com

The service manual outlines some of the detail on the sensor:

The 1998 update to the service manual gives some detail on how the speed sensor works:

Given that is pulses rather than a voltage you may need a scope rather than a meter to test it.

Good luck

 

[peace4uno]

Not sure I can be a lot of help but here goes

Henk stocks a few speed sensors so may have the right one for your model, I agree that it is likely to be 46403099

Mechanical Parts – Page 16 – Barchetta Parts

barchettaparts.com

The service manual outlines some of the detail on the sensor:
View attachment 427031
The 1998 update to the service manual gives some detail on how the speed sensor works:
View attachment 427030
Given that is pulses rather than a voltage you may need a scope rather than a meter to test it.

Good luck

I agree that it is most likely puls, but the puls is a on off voltage signal. Like 0 or 5 volt. That is what I think, and what many YouTube videos are about. Still I’m not 100%. Since there is active an d passive. Puls and constant variants. I can’t find the difference on the sensor documentation(none)

When you wrote Hank, any website address?

 

[brianpoole]

part number 0046403099 is amongst these other Barchetta parts for sale

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Having trouble with my speedometer I also had to replace the gearbox spline drive

https://www.autodoc.co.uk/car-parts/oem/7754074

 

[Wiltshire Chris]

When you wrote Hank, any website address?

The link is in my original message

part number 0046403099 is amongst these other Barchetta parts for sale

Looks like @brianpoole can help you, I'd recommend him as a good source of parts.

Out of interest the change between the two parts is how the connector is attached to the sensor. You can see the two different versions in the manual pages I posted earlier and in ePer (part 1 is the older sensor, part 7 the newer one) :

ePer describes the change 5180 that brought in the new version as "NEW SPEEDOMETER PULSE GENERATOR WITH CO-MOULDED CONNECTOR (DAT 15/10/2001)" which describes the change well. The sensor went from having a small tail wire with the connector on the end to having the connector moulded on to the sensor. I suspect the operation of the two sensors is identical and that it is just how the connector is attached that has changed. Both manual sections state it is a hall effect pulse sensor.

 

[peace4uno]

That is what I suspected also, that the mekanical part of the sensor is identical. Connection to the gearbox that is. The wiring, and the output signal should be the same. So, if I use a newer sensor, with no wiring, and this is connected with 3 pins, it should work the same way. And the signal to the speedometer is the same, and at the end the speedo should work. If everything else is in order

Anyone that have any other thoughts on this issue?
Anyone that have measured the output signal, and can give me the voltage that is expected. 0-5 volt is what have read on my voltmeter. Input, is about 9

 

[ruxi2k]

Hello

I also had the problem with the speedometer.
I tried to change 2 sensors but it still doesn't work.
Then I understood that the problem is with the indicator on the board.
I changed 3 second-hand boards until I found one that would work.

I know many B owners who have the same problem because of the dashboard indicator.

 

[peace4uno]

Hello

I also had the problem with the speedometer.
I tried to change 2 sensors but it still doesn't work.
Then I understood that the problem is with the indicator on the board.
I changed 3 second-hand boards until I found one that would work.

I know many B owners who have the same problem because of the dashboard indicator.

Thank you for the response, but I´m not sure what you mean when you say dashboard indicator. Is some part of the speedometer, or is it the speedometer as one whole part?

 

[ernibv]

Henk at Barchetta Parts has a good friend (Paul?) who is specialized in dashboard diagnostics and repairs. He also has a test unit. Very nice guy. grtz ER