Technical Tacho fault, Just had to change out the nearside light cluster due to a mot failure caused by the adjuster not working.

[EBarson]

Tacho fault, Just had to change out the nearside light cluster due to a mot failure caused by the adjuster not working.As luck would have it , the indicator bulb blew while I was testing it before bolting it back into position. So when I turned the ignition on I got a clicking with the word Batt in the lcd display and the rev counter rotated . I figured I had blown a fuse when I noted the hazards were not working along with the indicators. Eventually found the blown fuse, so indicators now working. However the rev counter no longer returns to zero it sits a 2 and behaves as if that is zero. Does anyone know why and how to fix it? I tried disconnecting the battery for 15 mins but no luck.

 

[bugsymike]

Tacho fault, Just had to change out the nearside light cluster due to a mot failure caused by the adjuster not working.As luck would have it , the indicator bulb blew while I was testing it before bolting it back into position. So when I turned the ignition on I got a clicking with the word Batt in the lcd display and the rev counter rotated . I figured I had blown a fuse when I noted the hazards were not working along with the indicators. Eventually found the blown fuse, so indicators now working. However the rev counter no longer returns to zero it sits a 2 and behaves as if that is zero. Does anyone know why and how to fix it? I tried disconnecting the battery for 15 mins but no luck.

Just a guess, but possible re "initialsing" the BCM by the use of Multiscan program may help. Try someone in the "multiscan" area of the forum for better advice.

 

[portland_bill]

Tacho fault, Just had to change out the nearside light cluster due to a mot failure caused by the adjuster not working.As luck would have it , the indicator bulb blew while I was testing it before bolting it back into position. So when I turned the ignition on I got a clicking with the word Batt in the lcd display and the rev counter rotated . I figured I had blown a fuse when I noted the hazards were not working along with the indicators. Eventually found the blown fuse, so indicators now working. However the rev counter no longer returns to zero it sits a 2 and behaves as if that is zero. Does anyone know why and how to fix it? I tried disconnecting the battery for 15 mins but no luck.

I think the tacho is really just a voltmeter, taking a signal from the BCM or engine ECU. When it went full scale, that suggests a voltage spike. If there's a stop at the end of the scale, it is possible that the needle hit that, and slipped on its spindle. Apparently by 2000 rpm. If this is the case, it will require the clocks to be dismantled, and the needle carefully repositioned on its spindle. If it otherwise seems to work OK, but is just 2k above the expected reading, that would seem to confirm this theory.

 

[Communicator]

The OP has not stated which version his vehicle is. I am inferring x250 or later. I do not have direct experience of the x250, but on the earlier x244 the analogue indicators are driven by stepping motors. I see no reason for Fiat to revert to voltmeter type innstruments on later models. If the drive units are in fact stepping motors, then the action suggested by @bugsymike may be more likely to solve the problem.

 

[portland_bill]

The OP has not stated which version his vehicle is. I am inferring x250 or later. I do not have direct experience of the x250, but on the earlier x244 the analogue indicators are driven by stepping motors. I see no reason for Fiat to revert to voltmeter type innstruments on later models. If the drive units are in fact stepping motors, then the action suggested by @bugsymike may be more likely to solve the problem.

It could still be the case that if the dial has a physical stop, and the needle has hit it, the needle can slip on its spindle.

 

[EBarson]

I had come to the conclusion that it was some sort of mechanical problem with a shifted spindle and you all seem to agree. I will remove the panel and report back

 

[Anthony489]

Hi

I believe (as Communicator says) that age of Ducato uses miniature stepper motors for the instrument dials. These have a tiny rotating part which is "nudged" clockwise or anticlockwise by applying pulse sequences to a couple of magnetising coils. The rotation is then geared down and used to turn the pointer. In principle, the drive electronics can always tally the up and down pulses so it will never "lose its place". However, I suspect that for an automotive application the motor also has a mechanical end stop so that periodically the motor can be driven to and against the end stop (e.g. at the zero position) and the driver then "knows" where it is. This might happen every time its powered up, but that's just a guess.

It would seem that either your tacho needle has slipped on its shaft (probably only a friction fit) or the plastic gears inside have slipped, so that the instrument zero stop and the pointer zero no longer coincide. If this is the case, powering off and on or resetting the driver won't help as the fault is within the motor. You might be able to take the cluster apart and gently move the needle back round, otherwise you will need an instrument repair specialist to do it for you.

 

[EBarson]

I am going to try and carefully take it apart and reset it, will update the thread when I have.
Many thanks

 

[HughJampton]

I am going to try and carefully take it apart and reset it, will update the thread when I have.
Many thanks

Fitting Lockwood's overlays requires partial disassembly of the needles (Speedo and rev counter). The instructions for this also imply that the "stop" position can be adjusted (and how to do it).

Apologies if these instructions aren't quite the correct model (most are pretty similar, and I'm mobile at the moment) but you might find them useful.

https://lockwoodinternational.co.uk/wp-content/uploads/2020/01/C120_C1179_C1181_etc_8329-8332_Fiat_Ducato_etc.pdf

 

[EBarson]

The cure, many thanks to all who posted suggestions, turned out to be quite simple in the end. I had to remove the instrument cluster and that required removing the four screws that held it down. the two at the front were hidden under the two black panels either side of the steering wheel, one of the panels contained the headlight adjuster switch. Having released the the panel on the rear are three colour coded plugs which are held in with levers which are locked with small tabs. depressing the tab allows you to rotate the lever and pull out the plugs. Next I undid the three screws that held the instrument cluster. The clear panel, which is held by several small tabs, came off next. I was then able to simply push, very gently, the pointer back to its correct position. I reassembled it in the reverse order. Be very careful with the clear panel as I managed to break two of the retaining tabs. I put the plugs back in then started the engine to see it the panel still worked, which it did, then replaced the unit and screwed it back in place.
I am still baffled as to why an indicator light blowing and taking the fuse with it should cause this problem but at least I was able to fix it.
Again many thanks for the suggestions