Technical Speedometer and tachometer weird issue...

[Stholt]

Hi all, back with an odd one. The speedometer and the tachometer are acting weird. The speedometer only reads up to about 20 and seems to be measuring at 1/4 what we are travelling. The tach hovers between 2000 and 3000 rpm while driving, and does not go above 3000.

I have recently changed the alternator and the starting battery. I did remove the instrument cluster during the alternator install(chasing a issue caused by a faulty new alternator), but I believe everything went back in place. The starting battery was 9 years old and not holding a charge so I changed that as well. There are 2 lights on the dash for the ASR and ABS, which I believe is down to a speed sensor, but have not had the chance to check each one yet, but those lights were one before and the gauges worked fine, so I am not sure if they are connected to this issue. Odometer is reading correctly and the other dials seem to be functioning just fine.

Any thoughts? I didn't think a 2006 would have any sort of body module reset procedure for replacing the battery.

 

[bugsymike]

Hi all, back with an odd one. The speedometer and the tachometer are acting weird. The speedometer only reads up to about 20 and seems to be measuring at 1/4 what we are travelling. The tach hovers between 2000 and 3000 rpm while driving, and does not go above 3000.

I have recently changed the alternator and the starting battery. I did remove the instrument cluster during the alternator install(chasing a issue caused by a faulty new alternator), but I believe everything went back in place. The starting battery was 9 years old and not holding a charge so I changed that as well. There are 2 lights on the dash for the ASR and ABS, which I believe is down to a speed sensor, but have not had the chance to check each one yet, but those lights were one before and the gauges worked fine, so I am not sure if they are connected to this issue. Odometer is reading correctly and the other dials seem to be functioning just fine.

Any thoughts? I didn't think a 2006 would have any sort of body module reset procedure for replacing the battery.

@Communicator will probably be the man to advise on this if available.
I suspect it is whatever was disturbed at the instrument cluster.
By the way some vehicles use a pickup from the alternator to drive the rev counter, not sure if that is the case with Ducato, but you did indicate an issue after fitting the alternator, was it a "like for like " swap or a cheap pattern one?
Re the ABS often it is a sensor at one of the wheels, but you need to test before just replacing. Occasionally the ABS computer on the ABS pump can have a problem , but even then it is more likely to be a wiring or poor connection.
I can't see changing the battery being a problem on your age of vehicle.

 

[Communicator]

Nothing stands out as a possible cause. On the x244 model, the speedometer and odometer use the same pulse train, which is generated by the speed sensor on the final drive. Possibly a poor connection at the instrument panel connector could be reducing the pulse amplitude to a point where the spee signal level is inadequate for the speedo. The rpm indication i.s derived from the crankshaft sensor via the ECU. The engine is running, so ECU must be receiving pulses from the crank sensor.

A common factor is the instrument panel connector "D" which carries both signals and the positive supply, as it has been disturbed, perhaps worth reseating after appling contact cleaner to the connectors.

On the x244, there is no need for any special procedure when reconnecting the battery, except for resetting the clock, and if necessary applying a code to the radio.

From eLearn, when ABS option is fitted it replaces the load proportioning valve for the rear brakes. This facility does not work when the ABS is faulty. You are advised to drive with care in such circumstances.

 

[Stholt]

Thanks for the suggestions...odd though, this morning I went out to sort a couple things on the campervan. First was a brake light bulb that wasn't working, turned out to be the connector had come loose from the back plate and just needed to be reseated...but when I went to check to make sure the bulb was working, the tach and speedo are now working fine...weird. I know I should keep looking for what caused it, but intermittent electrical issues are a nightmare. The negative battery cable feels fairly stiff, so I might replace that if I can find the proper replacement. Mine has the flag connection in the middle and I am having a hard time finding that one.

 

[Stholt]

Last reply...the issue did not fix itself, I just didn't get it up to a high enough speed while checking. I did pull the cluster out today to see if maybe a wire had come loose or something and noticed this:

the backing for the cluster was bulging and catching the needles...couldn't really see it while it was installed, but a few bits of 2 sided tape and it is all sorted.

 

[Communicator]

Thanks for the suggestions...odd though, this morning I went out to sort a couple things on the campervan. First was a brake light bulb that wasn't working, turned out to be the connector had come loose from the back plate and just needed to be reseated...but when I went to check to make sure the bulb was working, the tach and speedo are now working fine...weird. I know I should keep looking for what caused it, but intermittent electrical issues are a nightmare. The negative battery cable feels fairly stiff, so I might replace that if I can find the proper replacement. Mine has the flag connection in the middle and I am having a hard time finding that one.

The connection at the flag terminal is the main chassis earth. Mine has had an application of vaseline aimed a preventing moisture ingress both to the connector, and the cable.. You could consider two cables meeting at the chassis earth, or battery terminal. With the second option, a slightly thinner cable could be used to connect to the chassis earth, as it would not be carrying starter, or alternator currents.