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Rev / Tacho has stopped working

Palletpallet

New member
Joined
31 Mar 2021
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16
Hi all, I wonder if anyone else has had to deal with (and hopefully know how to fix) a faulty rev/ tacho gauge?

About a month ago the gauge was reading about 1000/rpm less than it should. A simple "shut down restart" solved the problem and all had been well since.

Today I use the car for the 1st time in about ten days (as I have been out of the country) and she started fine, but the rev gauge is not reading at all this time.

The old shut down & restart (about 5 times) has had no effect either.

To be honest, during the 25 mile run it did show about 400rpm for a few seconds, but flicked a millimetre or two when revved for 99.9% of the drive.

Does anyone have any idea where to start problem solving this please?

Any assistance is well appreciated.
 
To be honest i've never seen this fault before but logically its a wiring plug or the rev counter itself that's the issue with the rev counter being the most obvious .

To the best of my knowledge you can't replace just the rev counter , porsche dont sell them , so a remove of the cluster and send to a company that can repair them is the cheapest option .

The fault needs to be diagnosed first though .. often a fault code readout of the instrument cluster will say there is an issue .
 
Thanks deMort, I'd narrowed it down to the same issue. I've found a local (ish) company who can test them first and if needs be repair them and I'll be sending it off later this week. I'll feedback the outcome.

Thanks again.
 
Hi - what was the outcome of this?

My oil pressure gauge is all over the place. Had a new sender unit installed and run new wires to the loom - so we think the fault in in the instrument cluster.
 
Well interestingly it started working again (most of the time). The first repair bloke claimed it was a chip failure and unrepairable - and gave it back to me without any test costs... I don't think they did anything to be honest and just sat on it for a week.

I've only used the car three times since the last post.

However when the car is warm, a key off / key on restart fixes it. If it was a chip failure it would expect it to be dead all of the time???

Also if I don't let the revs drop back to idle at start up (so just leave it at 1500rmp for a minute / or drive off and don't let the revs drop fully during a gear change) the tacho works perfectly. Very strange. the ECU is seeing the right rev readings as I've plugged in a diagnostic machine, so it has to be just the cluster or wiring to it.

Still it is annoying so I'm sending the cluster off to another specialist on Monday for testing (and hopefully repair).


What is your pressure gauge doing? Any scenarios where you can replicate the issues? I mean they move up and down due to engine temp and revs anyway right?

I changed mine before the dash fault as mine always read +2 bar with ignition on, but engine off! It works fine now though.
 
davenwalk said:
Hi - what was the outcome of this?

My oil pressure gauge is all over the place. Had a new sender unit installed and run new wires to the loom - so we think the fault in in the instrument cluster.

Or new unit is faulty too?
 
davenwalk said:
Hi - what was the outcome of this?

My oil pressure gauge is all over the place. Had a new sender unit installed and run new wires to the loom - so we think the fault in in the instrument cluster.

Oil pressure sender is a variable resistance , a potentiometer .. its gives short to earth of varying resistances depending on position .

if you have changed the sensor and the wiring you are left with 2 possibilities ..

There is a blockage in the oil way to the sender or the pressure is varying which an oil pressure gauge on the engine would confirm .. oil pressure would increase and fall

Or you have a fault with the gauge .. this might be the gauge or the power feeds / earth to it .

For me i would put an oil gauge on the engine in place of the sender to confirm that side is correct .. i would then flag it as a gauge fault .. wiring diagram to confirm there are no separate feeds for just this gauge which i doubt as it tends to use a universal feed / earth then its the gauge that's left .
 
deMort said:
davenwalk said:
Hi - what was the outcome of this?

My oil pressure gauge is all over the place. Had a new sender unit installed and run new wires to the loom - so we think the fault in in the instrument cluster.

Oil pressure sender is a variable resistance , a potentiometer .. its gives short to earth of varying resistances depending on position .

if you have changed the sensor and the wiring you are left with 2 possibilities ..

There is a blockage in the oil way to the sender or the pressure is varying which an oil pressure gauge on the engine would confirm .. oil pressure would increase and fall

Or you have a fault with the gauge .. this might be the gauge or the power feeds / earth to it .

For me i would put an oil gauge on the engine in place of the sender to confirm that side is correct .. i would then flag it as a gauge fault .. wiring diagram to confirm there are no separate feeds for just this gauge which i doubt as it tends to use a universal feed / earth then its the gauge that's left .

Thanks DeMort, sorry I should have mentioned. That's exactly what we did, manual gauge confirming there is nothing wrong with engine or oil way. So thinking it's the gauge or electronics around the gauge...

Anyone with any experience with the instrument clusters? Decent / reliable place to look at faults as im sure replacement will be prohibitively expensive...
 
I have used these people to repair my nav DVD unit. Excellent service and happy to give you all the info you need. Reasonable prices too. Post it to them or hand deliver.
https://www.revtronic.com. :thumb:
 
It's fixed!

Just a quick update.

So over the winter the car was barely used, but when it was, the tacho would rarely work. I decided to send it off a couple of weeks ago (for the second time and to different company) and for a very reasonable sum, they have resolved the issue. I used the car a lot this weekend (circa 300 miles) and not once did it drop to zero or misread.

I'm really pleased with the service from Autotronics. I'd highly recommend them.

It's great to see the needle dancing around as you give it the beans again. :D
 
Good result & recommendation
 

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