tach signal?

aibast · Post by **aibast** » Tue Mar 20, 2007 10:07 am

Where does a tach get its signal. I have a problem here that id doesn't work sometimes. Most of the time is perfect and works proper but sometimes just drops away and show nothing. So whet is the signal source on these things. So I could trace the wires. I think the gauges have no problem all other things work perfect. And yes I did try the search function

crispy-d · Post by **crispy-d** » Wed Mar 21, 2007 2:56 am

Hello there, I thought the tachometer gets its signal from the gearbox, but having searched I now understand that it is directly connected to the ignition unit. Mine does exactly the same, moreso in cold, wet weather. This was the first time I discovered the use of clubman_dan's percussive maintenance. I find a knuckle-whip to the curved perspex does the job, but can leave bits of skin and blood obscuring the dials...

I now don't care as much, as there are worse things wrong with the car at the moment, and usually the signal pops back after a short while. But I've heard it's usually the connection at the back of the dial. But if you have checked this, then maybe it is down by the gearbox. Best of luck with it anyway!

Crispin

rpruen · Post by **rpruen** » Fri Mar 23, 2007 2:26 pm

The signal is from the ECU, if it goes missing, then the car won't work at all as the fuel ECU uses the same signal to time the injection pulse.

It's a loose connection on the instrument cluster itself. Either a poor solder joint or the connector pins that go from the main PCB to the intruments themselves.

Some people reccomend soldering the pins at the back of the dash that connect to the istruments. If you do that then it is impossible to remove the PCB in future.

Remove the PCB and clean the pins. Use some silicone grease, or dilectric grease to prevent bad contacs in the future.

Richard