Speedometer

Will i be able to do this myself or does it need experienced mechanic

There are only two usual speedo failure problems: a broken drive cable (older cars generally) and a failed electronic sender unit (later stuff).

I am fairly sure that you have the electronic type and if the wiring hasn't fallen off, then you need an electronic sender unit , easy to buy and easy to change, one bolt (possibly none) and a wiring plug.

I would get one from a breakers.

mrcheerful

I've had to buy one for a Fiat. It was only £17.

My 306 (1998) speedo has gone a bit bonkers recently. It's almost as if the dial is sticky. I believe it's fully electronic. It's only started last week when we've had cold weather. The speedo basically will go upwards but not down again. So 0-30 gives you a 30mph reading, then

30-0 still says 30. Then 0-30 again increases the reading by 30mph to 60mph, and so on until it's right the way around pointing downwards. It only seems to improve after sometime of driving (maybe just 5 minutes when not too cold/cleared itself earlier in the day up to 30 minutes+ if very cold). When it gets better what happens is the speedo will start to react when decelerating, ie. it goes down again. But when you get stationary, it's still reading 80mph+. Turn the ignition off and it then judders back to 0. Restarting and driving off again will then be fine for the rest of the journey - until it seems to get cold/left for a while and then it might happen again.

What might be the cause of this? I'm wondering if the needle/dial is just sticky and improves when warmed up.

Thanks

D

Sounds like a dry solder joint on the instrument's circuit board.

Tip: never catch a falling soldering iron. The /floor/ will not feel pain.

Andrew

Would really a dry solder joint show up like this - that it always gets better when car has warmed up? I'm quite happy to try re-soldering everything if necessary - but I've no idea the number of components, their size, or practicality of doing it as I've not had the instruments out yet.

D

[...]

Your foot might!

Chris

Well, you could try hitting the general area when it's playing up and if you can make it start working then a dodgy connection would appear to be the cause.

I can imagine some sort of Heath Robinsonian mechanism with little ratchets and pawls being engaged/released according to the position of a pendulum, but that would surely have gone wrong much sooner. Hmmm... just a minute :-)

Or does it look like the needle is really close to the plastic covering it? Perhaps if a smaller hit in the area of the needle tip made it work then that would be suggested, rather than a larger hit to get some movement to the electronic components.

Andrew

I'm sure my toes aren't flexible enough to catch a soldering iron :-)

/However/, a couple of times when I've been drying up dinner plates and managed to let one slip, raising a foot slightly off the ground to stop the plate hitting the floor has saved said plate. If you don't raise your foot, it hurts.

Andrew

I don't do drying up, so I'll have to take your word on this one.

It might be a solder joint but a better bet (as it's a 306) is check the engine earthing strap. It sits between the engine and chassis near the battery and tends to fracture after some time giving weird instrument readings as it fails and eventually running problems. Just replace with a new one, clean the contact areas before putting in the new one and put a little vaseline over the bolts when done to help keep the prevent the joint corroding too fast.

Chris