Technical Speedometer

[Norge]

I have a 1996 Fiat Ducato 230. 2.5 turbo diesel. I'm struggling with the speedometer dancing up and down. I disassembled the cable, which was completely damaged. Almost torn completely. Replaced it with a new one. It got better, but the needle still bounces up and down. Does anyone have experience with this?

 

[bugsymike]

I have a 1996 Fiat Ducato 230. 2.5 turbo diesel. I'm struggling with the speedometer dancing up and down. I disassembled the cable, which was completely damaged. Almost torn completely. Replaced it with a new one. It got better, but the needle still bounces up and down. Does anyone have experience with this?

If yours is the older cable drive with no electrics then all you can do is oil the inner cable and ensure the cable has gentle curves, no tight turns to cause strain.
In the old days it was common for us mechanics to remove the cable and re oil it on older vehicles as cables dried out. I used engine oil from an oil can, not something like WD40 as to light and dries up.
I assume a complete new cable and not just the inner cable fitted into a older possibly damaged outer.
The other thing is if you have the end of the old cable you could try fitting it into the speedo head and turn to ensure no partially seizing at the speedo it's self.

 

[Communicator]

I have a 1996 Fiat Ducato 230. 2.5 turbo diesel. I'm struggling with the speedometer dancing up and down. I disassembled the cable, which was completely damaged. Almost torn completely. Replaced it with a new one. It got better, but the needle still bounces up and down. Does anyone have experience with this?

I cannot claim recent experience, but I seem to remember something from my youth which was a long time ago.

Flexible drive should be well lubricated, and routed to avoid any tight bends. I believe that the speedometer itself employed some form of damping, which could be either mechanical, or by viscous fluid on the needle pivots.

 

[Norge]

Thank you for the response.It's the old style without electronics. The cable going into the speedometer is new. However, this is a system where a cable runs out from the gearbox and is joined with the speedometer cable underneath the car. It could be that the cable coming out from the gearbox is the issue. I'll get under the car and check this cable today.

 

[Norge]

I disconnected the cable that was attached to the gearbox. Connected directly from the speedometer. Don't know what the cable in the gearbox is for. There were 2 wires connected to it. It improved but not completely. The speedometer needle still fluctuates slightly. However, I'm unsure about the connection of the cable to the speedometer. I bought a used speedometer and it came with a plastic sleeve that I didn't have on mine. I also can't attach the cable to the speedometer when using this plastic sleeve. Any ideas? I'll attach some pictures.

 

[Communicator]

If you can connect your new cable directly to the gearbox, without tight bends, then that would make sense.
I am wondering whether the "gearbox cable" has been removed from an x230 fitted with a common rail engine., which would have beeded a sensor for road speed. Alternatively an aftermarket automatic reversing light switch (Why?) or trip computer.I do not have any thoughts about the plastic sleeve at the rear of the speedometer, but others may have met this.

Can you try your spare speedo to see if it gives a steady reading? Also you could use it as a learning aid , to check for damping mechanism.

 

[Norge]

Thank you for your response. Good theories. It's possible it could also be due to the need to monitor the vehicle's speed. An aftermarket cruise control was previously installed on this car. I'm increasingly inclined to believe it's related to the connection of the cable to the speedometer. I really don't understand how this sleeve could fit. Could there be multiple types of speedometer cables for this? I have tested both speedometers, with the same result. I need to get it through inspection. It's currently off the road

 

[Communicator]

Thank you for your response. Good theories. It's possible it could also be due to the need to monitor the vehicle's speed. An aftermarket cruise control was previously installed on this car. I'm increasingly inclined to believe it's related to the connection of the cable to the speedometer. I really don't understand how this sleeve could fit. Could there be multiple types of speedometer cables for this? I have tested both speedometers, with the same result. I need to get it through inspection. It's currently off the road

Cruise control most likely reason for extra drive cable and wires. Back to original problem, is speedometer input shaft free to rotate?

 

[Norge]

Cruise control most likely reason for extra drive cable and wires. Back to original problem, is speedometer input shaft free to rotate?

You mean inside the speedometer?. Yes, when I insert the plastic sleeve and rotate it with my fingers, it rotates smoothly and the speedometer needle jumps up.

 

[Communicator]

You mean inside the speedometer?. Yes, when I insert the plastic sleeve and rotate it with my fingers, it rotates smoothly and the speedometer needle jumps up.

Just trying to think "outside the box" for you. Could it be that the speedo drive gear in the gearbox is worn? Fixing is typically an M7 bolt, needing an 11mm spanner. Be warned, I have read that it is possible to loose the gear inside the box when replacing. Some grease is reccommended to retain gear on spindle, if needed.

I wonder whether @bugsymike has any thoughts from his extensive practical experience?

 

[Norge]

Just trying to think "outside the box" for you. Could it be that the speedo drive gear in the gearbox is worn? Fixing is typically an M7 bolt, needing an 11mm spanner. Be warned, I have read that it is possible to loose the gear inside the box when replacing. Some grease is reccommended to retain gear on spindle, if needed.

I wonder whether @bugsymike has any thoughts from his extensive practical experience?

I agree that it's an alternative. However, I'd like to wait until everything else has been tried, as it involves some uncertainty regarding the job of replacement. For now, I think I'll go ahead and schedule the MOT test and try to get it approved. The speedometer needle is definitely better than it was, and there's a chance it will pass inspection. If it doesn't pass, then I'll try to figure out the plastic sleeve issue and see if that's the solution. As a last resort, as you mentioned, I'll consider replacing the gears inside the gearbox. P.S. I've now scheduled the inspection for this upcoming Friday. Thank you for your help and support. I really appreciate it.

 

[bugsymike]

Just trying to think "outside the box" for you. Could it be that the speedo drive gear in the gearbox is worn? Fixing is typically an M7 bolt, needing an 11mm spanner. Be warned, I have read that it is possible to loose the gear inside the box when replacing. Some grease is reccommended to retain gear on spindle, if needed.

I wonder whether @bugsymike has any thoughts from his extensive practical experience?

I agree with you @Communicator re possible cruise control so if possible to bypass it may help.
If it was a work van I would have said some form of tachograph.
Just come back from endoscopy job and not on my vehicles , so not feeling to frisky.

 

[Norge]

I decided to go through the entire speedometer system today before tomorrow's inspection. When I was under the car and felt the connection into the gearbox, I could tell that the cable wasn't completely tight. I tightened it and took a drive. Now it's completely fine. 100% stable. All good