Stroppy Speedo

[Alias]

Morning all,

Just starting using the 172 as my daily and shes decided that she doesn't always want to tell me how fast I'm going. Its been doing it on and off for a little while now and normally if you ease off the throttle the needle jumps back to life and carries on like nothings happened. This morning she wasn't having any of it.

The rev counter and fuel gauge etc all still seem to work so presume its just going to be a sensor somewhere. If anyone could shed some light on the problem it would be much appreciated.

Also, sorry to anyone stuck behind a really slow clio during the average speed section of the A12 by Witham this morning, it died right before the first camera and came back within half a mile of getting back to normal speed!

 

[-J-]

Ive got the same issue with my Cup.

It's the Speedo sensor located on the Gearbox I believe.

 

[Cub.]

Yep, take the speedo sensor out and if its covered in gearbox oil clean it, then pop it back in. If it doesn't fix it, then you'll need a new one, but they are only circa £15 I believe.

The speedo sensor is located in a metal clip, at the back of the engine on top of the gearbox. It will take a reasonable amount of effort to pull it out once you have undone the metal clip. Make sure its pushed in fully when you put it back in, before doing the metal clip back up.

I have to do a bit of work to mine later, so while I'm out there I'll take photos of the speedo sensor : its location and put them on this thread if it helps.

Edit to add - this is only for Cups, ph1 and early mk2s. Later mk2s the speedo is done from the ABS rings so the above won't apply.

 

[adamlstr]

When it does this, chuck it in 5th, then double the number on the rev counter.

2500 rpm = 50mph
3000 rpm = 60mph

Roughly.

 

[Cub.]

Right, as promised. Photos.

This is what a speedo sensor looks like when out. Bottom pointy bit goes in the gearbox, will have oil on it. Clean the oil off;

Look down the engine to the right of the coil pack;

And you will see this. Speedo sensor is in the metal heat shield / bracket with the 'c' shaped cutout for the cable in the middle of this photo.



5 min job to change, and if you need a new one, they are circa £15 iirc....

 

[Alias]

Thats awesome, thank you. Might even be able to have a look during my lunchbreak.

 

[Cub.]

Unclip from bracket / heat shield, take cable plug out of the top. Pull speedo sensor out.