Board logo

mechanical speedo, does it need electricity?
smart51 - 18/12/07 at 08:37 AM

I've rebuilt my instrument cluster with a new recalibrated fascia. I connected a drill to the speedo cable and it took 8 seconds to coun't up 1/10 of a mile. Thats about 45 MPH. The speedo needle didn't turn at all. Does the speedo bit need power applied to work?

Humbug - 18/12/07 at 08:40 AM

Are there any lecky terminals (apart from lighting)? If so, you prolly need power!

David Jenkins - 18/12/07 at 08:43 AM

You'll need electrickery for the light - which you'll need to pass the SVA. You have to be able to read the speedo whether it's day or night.

smart51 - 18/12/07 at 08:46 AM

No, does it need electricity for the speedo arm to turn. The odometer counts up miles so I know the mechanical connection is OK. Its just that the speedo needle stayed still


It is a combined instrument cluster so there are lots of wires. My donor is in pieces and I'd have to plug everything back in to get the speedo working.

What I want to know is have I broken it by pulling the needle off and then pushing it back on again.

bonzoronnie - 18/12/07 at 08:49 AM

What car did the instrument cluster come from ? .

Cable driven speedo's are usually mechanical.

Ronnie

nitram38 - 18/12/07 at 08:57 AM

Did you turn the drill the right way?

Mr Whippy - 18/12/07 at 08:59 AM

did you put the needle back on behind the little peg and then lift it over the peg to set at zero? There should be a small dot about a cm anti-clockwise of the zero peg, put it on there and that creates the small amount of spring tension needed.

take a look at this mini speedo, see where it says H/B below is a small white line, that is where the needle should point when first fitted

[Edited on 18/12/07 by Mr Whippy] Rescued attachment mini_speedometer_001.jpg
Rescued attachment mini_speedometer_001.jpg

smart51 - 18/12/07 at 09:13 AM

I turned the drill both ways to be sure I was turning the right way. The odometer counted up 1/10 of a mile in the right direction.

I set the needle slightly below the peg for zero. There is no calibration mark. Even If Id set it too high or too low, I'd expect it to turn a bit.

Its off a piaggio X8 by the way.

Mr Whippy - 18/12/07 at 09:27 AM

oh well next thing then is to find the live and the earth wire and plug her in

02GF74 - 18/12/07 at 10:25 AM

quote:
Originally posted by smart51
I've rebuilt my instrument cluster with a new recalibrated fascia. I connected a drill to the speedo cable and it took 8 seconds to coun't up 1/10 of a mile. Thats about 45 MPH. The speedo needle didn't turn at all. Does the speedo bit need power applied to work?


To answer the question, mechanical speedo does not need power and works by using eddy currents from a rotating magnet.

I cannot work out from your post if you have taken the speedometer apart or not but the magnet is fixed onto the shaft so unlikely that is the problem.

The direction you should turn the drive is that same direction as the mph scale increases so if looking at it from the front as scale is clockwise, then drill must spin anti-clockwise.

smart51 - 18/12/07 at 05:08 PM

It turns out that I'd pushed the needle on too far and it was rubbing against the fascia. Pulling it back a bit made it work. Phew.