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MG MGF Technical - Road speed transducer

Can anyone tell me where the roadspeed transducer is located on my 95 'F'? I have an EPAS failure (my speedo isn't working, but will be fixed v soon) but now reading up I'd like to check all the inputs into the EPAS ECU. If anyone knows where the others are as well that would be gratefully received!

Clive
C Stevens

Clive, the speedo on a 1995 MGF is mechanical. The most likely failure area is the gearbox section of the three-part cable (unless yours is a very early MGF, in which case, it'll have a rare two-part cable - see here for a bit more detail on repair - http://www.mgf.ultimatemg.com/group2/DIY/Speedo_cable/index.htm)

The EPAS roadspeed sensor is a simple Reedswitch and magnet based signal generator built into the back of the speedo that'll generate a square-shaped signal wave - have a look at the wiring diagrams on Dieter's website - http://www.mgfcar.de/schedules/index.htm

HTH
Rob Bell

Rob do you think this is the point to connect the 'speed' wire of a GPS unit to?
Ted Newman

Thanks for that Rob

Clive
C Stevens

Rob,

Another quick question. I took out, cleaned, and replaced the EPAS fuse and the PAS is now working, but the speedo still isn't. If the transducer takes it's signal from the speedo, what's happening?

Clive
C Stevens

Ted, yes it is. I think Dieter has some instructions on his website for a speed-related volume control - and also for when he fitted his Becker Sat Nav :o)

Clive, if the EPAS is changing its level of assistance and still working with a faulty speedo, I'd be very surprised. However, it is possible that the EPAS has reset, and if you don't go too high with the rpm (I seem to recall that the fail-safe 'trigger' engine speed being around 2750-3000rpm), then the EPAS continues to function. There is this zone where the EPAS continues to work - perhaps to stop a fast idle tripping the EPAS fail-safe. I suspect you'll find out soon enough whether this is the case for you or not! :o)
Rob Bell

Thanks again Rob. I've now changed the speedo cable and all is well. I initially changed the rear cable, and the speedo worked but was 'twitchy', so after a great deal of knuckle scraping I changed the centre section as well and it now works great!!
Thanks for your advice, and I'm sure I will be calling on it again!

Clive
C Stevens

Rob, the speedo on my 2002 F Trophy has not been working all year, it "flicks" and "twitchs" all round the dial, it will rest at 0mph whilst I drive at any speed between 10 to 70+.

It will rest at zero for some time and I have often waited for the fail-safe mode to kick in, which to date it has not.

I have changed the tranducer and cleaned the cogs that go into the gear box, made no difference.

I believe that there is a thread, somewhere, that details similar problems on F's that have had none standard radios/cd players fitted and caused wires at the back of the dials to become loose, so I am looking to attack the wires in the dash via the central air vents and see what happens.

Any suggestions please.

Thanks
Geoff Champion

No problem Clive :o)

Geoff, I think that you're looking in the right areas - namely electrical. It is possible that there is a damaged wire or poor electrical connection somewhere - probably either at the sender at the gearbox, or at the instrument cluster.

Maplins does a good electrical contact cleaner - I'd recommend you try this on the connections too, as from what you're saying, the connection is at best intermittent.
Rob Bell

Thanks Rob

Been recommended name of auto electician, as I know nothing re electrics will let him have a go, I would not know where to start.

Will keep you informed.

Cheers
Geoff Champion

Yes please Geoff - I'd be very interested to hear where the problem is isolated, thanks :o)
Rob Bell

Car in tomorrow, watch this space!
Geoff Champion

If you disconnect the transducer/speed sender unit, so that no pulse can be sent down the cable and then drive at speed, what should happen?

I ask because when I looked at the wires behind the dash, via the vents and footwell, unable to see any loose connection (but i'm no EXPERT) put all back together, went for drive to see if by some miracle I had found/cured my problem, only to see the needle bounce more wildly around the dial( I assume HT pulses), I found on inspection of the gearbox that the cable had not been attached.

Effect on driving experience, nothing! I thought it would have effected the EPAS, PAS and fail safe.

Help/comments appreciated from one very confussed owner.

Geoff Champion

>connect the 'speed' wire of a GPS unit to?

Ted,
indeed, it's there
:)
http://www.mgfcar.de/navi/index.htm

Dieter

This thread was discussed between 26/08/2007 and 10/09/2007

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