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MG MGF Technical - EPAS and Speedo

Hi

I've just got my car back from the dealer after they did a few bits of work including replacing the clutch, downpipe, release bearing and a few other bits to cure some outstanding problems.

Driving in to work this morning I noticed that the speedo isn't working. I phoned the dealer and they asked me to bring it in so that they can sort it.

I have also noted that the EPAS is behaving oddly.. sometimes very heavy sometimes very light. Now I assume this is because the EPAS is getting an odd speed input but i thought it was odd that the speedos input and the one used by the EPAS are the same thing?

Can anyone shed any light on this?

Cheers,

Chris
Chris

Basicly your right, signal shared, EPAS should shut down at higher RPM (EPAS red light), if it is getting intermittant signals then it might think you are going very slowly and keep the EPAS on, if this is so then be VERY careful at speed as assistance will be there and if you swerve to avaoid something you will take far more than you expect to.

Will
Will Munns

You don't say how old your car is but I would guess from the symptoms it is MY2001-. The older cars have a mechanical drive for the speedo and the signal for the EPAS is taken from a reed switch mounted on the speedo. The rotating magnets in the speedo switch the reed switch on and off. If the speedo cable breaks or is disconnected then the EPAS assumes default mode after a few high revs and switches power assistance off.
On newer cars the signal for the speedo and the EPAS is generated in the gearbox so an intermittent cable failure may cause the EPAS to switch in and out. Possibly the cable has been damaged or the sender unit partially unplugged. Check the cable out. The colour is White/Orange.

Bruce
Bruce Caldwell

Bruce, both cars will do the same, as loose speedo cable may joggle the magnets
Will Munns

Irrespective of intermittent signal, the EPAS will still switch automatically back on, so long as engine speed is below about 3,500rpm.

This is normal operation Chris, under the circumstances of a non-functioning speedo.
Rob Bell

>the EPAS will still switch automatically back on, so long as engine speed is below about 3,500rpm

Not quite true, the EPAS will disable after engine speed has exceeded 3.5k for some small amount of time, it will come back on if it gets a signal from the wheels, if the linkage is poor the signal might be enough to switch it back on, but not enough to register on the speedo. The EPAS will switch back on when the ignition is turned off and on again.

Will
Will Munns

;o)

Will, the EPAS DOES automatically switch on - I know, because this is exactly what happened on my car when the speedo cable sheared in two. Returning from the midlands, down the M4 motorway, I could get the EPAS to switch out pretty reliably at 3750 rpm, and then have it switch back on, rather randomly, whenever engine speeds were lower than that, and maintained for a period of minutes.

The cable was completely duff, and there was no way that any road speed signal was getting to the EPAS.
Rob Bell

This thread was discussed on 24/01/2003

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