Technical Punto mk1 speed sensor advice

[theremotedr]

Hi,
Have had a search on the forum but did not find the answer.
Punto Mk1 T reg manual 5 speed.

When i start the car "and still stationary" the speedo sometimes goes from 0 to100 mph then back again,sometimes it just stays at 100mph.
I have also noticed "when stationary" the trip counter is rotating as if i was driving the car.
Looking at the gearbox at the back there is a tall round switch which has a blue cable about 18" long making a connection just below the air filter housing.
Does this sound like a fault with the speed sensor or is this not the speed sensor i have seen / or would it be something else ?
Hope you can advise as not sure where to start.

Thanks

 

[Lozzy08]

First off I'd clean up your battery terminals and and connections, plus any earth's you find ad see if the problem still persists. Failing that I wouldn't know lol.

 

[theremotedr]

I have unplugged the item that i have just described and the mph needle & trip counter has now stopped working.
Reconnected them & fault has re-appeared again.
So i think this must be the speed sensor but the question now would be is this the faulty item ??

 

[g r nicholson]

The speed sensor is at the rear of the engine on top of the gearbox. If your speedo is erratic and usually goes around the clock and back to a fixed ´speed´ then it needs changing. Its a bitch to get off!!! and I speak from experience! I now need to find a replacement. Anybody have any ideas because Fiat in Spain do not have any. Any help appreciated.

By the way, the problem with my power hood was that a new Ford relay is simply not up to the job!! I replaced with a Fiat item - no prob.

Richard in sunny Spain

 

[fingers99]

Try eurocarcare (Google will find) or/and Shop4Parts (likewise).

There may be a supply issue, in which case a scrapyard may help.