(T) Rev Counter not working

Voko · 23-06-2018

Hi All,

Does anyone know common failure points on the rev counter, ive seen posts on the speedo but mine works Ok. My rev counter doesn't work at all, its fairly easy to get down to circuit board level and probe with a multimeter, but apart from some tarnishing on the 4 nut connections to the servo (which I've cleaned up), all looks ok. There was a cracked/dry joint on the speedo circuitry....

Any tips to check appreciated,

Mike

StevePD · 24-06-2018

Perhaps investigate the pickup end of the rev counter signal. I am guessing here, hopefully someone will have had experience with this. Steved

Voko · 24-06-2018

I had thought about that, it seems less likely than the instrument cluster. I assumed the Rev signal comes from the ECU on 'modern' cars but perhaps not, I could also look at injecting a pulse train into the instrument, but that is stating to get a bit in depth....perhaps someone understands how the Rev counter gets its signal or there is a wiring diagram?

Ilkka · 28-06-2018

https://www.dropbox.com/s/bzhdtbagf3...anual.zip?dl=0

Here's the 1Gb service manual including wiring diagrams.

Voko · 29-06-2018

Thanks I'll have a look

Voko · 13-07-2018

Looking at the wiring diagram the Rev counter is fed directly from the ECU, so the next step will be to see if there's some kind of signal reading the back of the instruments with the engine running.....if there is, then I'll have to try and source a scrap instrument cluster, and swap out the circuit board....

Voko · 02-11-2018

I got round to having a look at this again...I built an oscilloscope kit from eBay, and confirmed there is a good pulse train being fed into the rev counter, and the 12 and zero volts are ok. That just leaves the rev counter circuit board or servo that drives the needle. Anyone got a scrap instrument cluster they could sell me, so I can swap parts out....I don't really want to spend a lot of money replacing the whole lot

Voko · 16-11-2018

I got a rev counter from barchettaparts.com, swapped the circuit board and.....hey presto....a working rev counter :-)

Robsbarch · 19-03-2019

Glad you got got rev counter working, was it easy to change the circuit board, did you have to buy the whole instrument cluster?

Voko · 19-03-2019

Just the small circuit board, although barchettaparts sent me the rev counter... Actually quite easy, just a few connectors, screws and nuts..... there's a guide somewhere around about repairing the trip counter, that gets you most of the way there, then it's pretty obvious.....

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