Another 306 issue - flaky tachometer

[TDIfurby]

First drive of the "new" 306 tonight and I noticed sometimes the revs were reading right, sometimes they were dead. Any idea where the car gets the revs signal from please?

If needed, the car is a 96 XR DT

[StoatInACoat]

Pull the clocks out and check the connections on the back. Check the wiring loom for breaks and corrosion at the bottom corner of the rad (can't remember which side and not got mine here to check)

[lamlam]

Crankshaft sensor. Usually located on the back of the engine, it is in my 405 anyway. If your reading is all over the place, thats the first place i would look. Its likely a loose connection or maybe even corroded in the plug. Not hard to replace the sensor. good luck

lamlam

[TDIfurby]

lamlam said:

Crankshaft sensor. Usually located on the back of the engine, it is in my 405 anyway. If your reading is all over the place, thats the first place i would look. Its likely a loose connection or maybe even corroded in the plug. Not hard to replace the sensor. good luck

lamlam

Thanks. The reading isn't all over the place though. It either reads the right revs exactly or just goes back to zero for a while, then will come live again. Its like an on/off thing, rather than a variable issue.

[Crease]

its the crank sensor mate! on the underneath of the gearbox, reading of the flywheel

my flywheel gets dirty as part of it is exposed and picks up the grime, so i spray a load of brake cleaner in it while its running ( i have access to lift in work though!)

its a 10mm to remove, but is tricky, pull it out and give it a clean, mine works as and when it wants to aswell!

[TDIfurby]

Does the crank sensor give any information to any other part of the car as well, or just the tacho?

[lamlam]

Its only the tacho. The crank sensor is basically a magnet that pulses as the fly wheel cogs come near it, generating power to the tacho. Like that last post, if your fly wheel has some dirt on some of the cogs, the reading will be out. I just changed my crank sensor and it was very easy to do, just an open ended 10mm and a standard car jack is all you will need. I'd spray brake cleaner on the cogs and also take out the crank sensor and clean it up a bit, you should be golden.

lamlam