Speedo gone wrong?

[AndrewBClarke]

Quickie  - driving home yesterday my VDO speedo suddenly went from 30mph (rare slow speed) to 140mph or top of the scale. Is it likely to be the speedo itself that needs changing or a wiring issue? It might be if no relation but the milometer LED readout takes a while before it displays anything and even then is unreliable even though it keeps the reading correct. Andrew

[Mighty Mart]

Sounds to me as though you have a speedo cable issue? Have you got a right angled speedo drive? I haven't, and the cable has to bend too tightly in the tunnel without one. A new cable works ok for a short while, and then exhibits the symptoms you are describing.

Mart.

[AndrewBClarke]

Mhmm. No idea. Will have to look. I know it has a sender on the rear prop shaft so assumed it was electronic so no speedo cable as such. 

Checked and no speedo cable. All electronic using a sender. 

Thanks anyway!

[fossett]

Hi,

I've had this, i think its due to moisture build up during the 'off season'.

Leave your side lights on at every opportunity and there heat from the bulbs will help to dry it out, failing that, a trick often recommended here is to try removing it, submerging it in rice (dry not wet) and putting it in your airing cupboard for a while.

[Mighty Mart]

Ah, ok. If electronic, definitely not a cable issue....

hope you get it sorted ok...looks as though you've been oriented in the right direction despite me throwing you a curve ball initially lol...

Mart.

[AndrewBClarke]

On the positive, 0 to 60 is better - now about 1 second! Top speed of 140 mph in 3 seconds from a standing start is also not bad!

[Julie Hall - WSCC AO Representative]

I had a similar issue a couple of weeks ago, Andrew. I was merrily driving along and my speedo suddenly showed a very low speed, and then went down to nought. It sorted itself out and just returned to normal after a stop and a restart.

My LED reading is very hit and miss all winter too, that's kit cars for you.

So now you have an excuse to pop out tomorrow and see if it is still the same. 

[Dave-P-H]

My speedo did the exact same thing at the weekend. Usually the digital display disappears over the winter but it's the first time the speedo has done this. 

Got home, left it parked on the drive for half hour, went back out and it was working OK, 

[Ray The Brake]

Looks like a VDO  trait  my speedo would show digital read out intermittently, outside temperatures have risen over the last couple of days problem has gone.

" Moisture" no evidence to prove either way so I'm puzzled 

[Welly Jen]

A poor earth connection to the speedo can also cause these sorts of effects.

Jen

[AndrewBClarke]

According to an aironautic engineer, a poor earth connection would cause the reading to go down to zero as a circuit would be broken. If the needle or reading goes up it is either a faulty gauge, sender or moisture.  I am going with the moisture problem to start with as it is the easiest (and cheapest) to resolve. I have used the car all winter so no idea why it should happen now. Not bothered about the mileometer but thought it might help with diagnosis. Roll on the warmer weather and we will see what happens!

[TAFKARM]

Echo the airing cupboard fix, the VDO speedos dont seem to like this weather. 

[AndrewBClarke]

Russ. The photo of your engine looked a bit more problematic than my speedo. What's up?

[TAFKARM]

Not sure, so I'm putting it in the airing cupboard overnight to see if that helps!

[Beez]

I had the same issue with the Megabusa, the problem was the prop-shaft had hit the sensor due to the prop-shaft flange bolts being loose and allowing the prop to vibrate.

The prop was actually MISSING a couple of bolts and the rest were just finger tight, I had only just picked it up from the old owner and thought he was obviously an idiot to let them get so loose!!! Though to be fair I seem to have to tighten them up after every sprint/track day as the bike engine and Westfield reverse box seems to vibrate them loose, even with loctite and locknuts, the metal not nylon version, fitted!!!