Speedo way out

[andrewaudi]

Hello all!

Anyone got any ideas about how to fix my speedo, which is currently about 10 mph out at 70 and 5 mph out at 30. I know that they aren't the most accurate things, but they aren't usually this bad.

Is there an adjustment on the dials themselves or is it likely to be a faulty speed sensor. It has 115000 on the clock, so I expect things will have gone off a bit over time.

My speedo has the computer built in. When I took it to bits, i noticed an adjustment screw next to the petrol gauge, would this affect it or would the screws on the back be the best ones to go for?

The wheels are 15" wheels, which I believe are a standard size for the car.

It's a 2.3 94 cabrio.

[RJS_90q]

I have a similar problem with my 90 quattro. I am basing my observation on the speed listed by a GPS system.
I have checked the same GPS system in a different car and it ties up with the speedo in the other vehicle therefore it seems that my speedo is out (it reads 'fast').

Not sure about any adjustments but I'll have a look at the workshop manual and see if anything is listed.

[jp_paul]

There is a mod that you can do to correct this common fault. See http://www.eveshamsquash.co.uk/audi/speedo.html for details. It basically involves adding a resistor to the circuit to modify the dividing ratio. I was going to do the mod myself but now i know that i'm doing 76 when the speedo says 85, it didn't seem to be worth the meither.

[devonutopia]

By a wheel/tyre size which still is safe for rubbing/clearance, but is around 10% bigger rolling radius. :)

[andrewaudi]

The new wheel sounds the simpler option, with less chance of killing my speedo (if you had seen me with a soldering iron you would understand!). I was thinking of sticking on a set of the audi a8 style 17" wheels, i suppose i could get tires about 10% bigger, or i could buy a cheapo gprs with an accurate reading and ignore my speedo.

My only concern is that this is the reason my abs is cream crackered and my cruise control!

Any ideas?