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MG MGF Technical - Tacho jumping around

Hi guys
the tacho on my 96f has decided to start jumping around. sometimes it works fine. Where does it receive its signal from and is this a commmon fault.
Not long ago had the car serviced could something of been moved.

thanks in advance
tony
tony

Hi Tony,

Those symptoms suggest the square end on the speedo cable has worn or rounded slightly, just enough to slip occasionally. Earlier cars have mechanical speedometers, the change to an electronic input came circa 2001 IIRC.

I can't think of any reason a service would involve the cable being loosened, but may be worth checking the connection to the gearbox. The connection to the instrument pod however is rather less accessible...

Good luck, sounds like a new cable will sort the problem. Check the Rebuild section of Andy Philips' site for an excellent guide to dashboard stripdown - http://www.sfforever.co.uk

Mike Hankin

Is it the tacho or the speedo?
Paul Y9MGF

Well spotted Paul ;o) My sleepy eyes obviously wren't working too well...
Mike Hankin

Tony, it is a signal from the MEMS that provides the tacho pulse signal. Not ever heard of this problem before on the BBS - so not sure where to help.

If you have access to an oscilloscope you should be able to track the fault to the cable or to the gauge (or the connection therein)
Rob Bell

Check for bad connections at the ECU big connector and at the instrument itself.
Although, there's a multiconnector on top of the fusepanel.

See for the white-black cable
http://www.mgfcar.de/schedules/sb9.jpg

HTH
Dieter
Dieter

thanks guys for your input. i will have a good look over weekend
tony
tony

problem sorted.

checked connector on the ecu as suggested.it seemed a bit loose but i moticed that that the white black wire was pulled tight compared to the other wires. in deed i was able to slacken the wire and push the wire connector home into its block

once again thanks
tony

> .... noticed that that the white black wire was pulled tight compared to the other wires.

:)
Fairly common Mad_ problem with the ECU connector wires.
Special with the thin wires.

BTW, while you are on the matter.
Check whether the cable tie with rivet is correct mounted to the ECU bracket lower location.
It often comes loose (or never was attached) and the whole harness appears to drop downwards. This applies the pull-effect you saw to some of the wires.
It led to intermittant high idle at my car (sensor wires related)

Remount it, if it's the same with your car. You need to unbolt the ECU bracket to get there with your hands. Check the Main Relais Connector fitment while you are on there.

before
http://www.mgfcar.de/mems1.9/harness_loose_sc02513.jpg

after
http://www.mgfcar.de/mems1.9/rivet_Dsc02523.jpg

Dieter

thanks Dieter.

will have a look as suggested
tony

This thread was discussed between 17/08/2005 and 21/08/2005

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