Alfa Pages

[Matt Stolton]

Many of you, myself included, have mentioned how the speedo works, sometimes erratically, and then drops to zero (well 20mph anyway). With the use of a small convincing object, eg one's hand smacking the instrument binnacle, life can sometimes be temporarily restored, until the next bump in the road. This fix is for you....

The speedo's electric motor is fed by two wires, black and red, which originate from a small rectangular circuit board, mounted on the side of the speedo gear/dial box. The wires are soldered on the motor, and attach to the PCB via a two way connector block. When the speedo is mounted inside the instrument panel, the rear of the motor sits inside an extension of the main housing. This causes the black/red wire to become caught, and stretched at right angles. This causes a break in the cable, and an intermittent connection. Mine was so bad, and been whacked so often, that charring from arcing was visible as a discolouration of the red cable, right where the 90 degree bend was!!!! Replace black and red cable, and speedo will work again. Providing of course, you don't have a dry joint on the PCB, but that would be really bad luck.

To stop it happening again, you can drill a new route for the cable out of the back of the speedo motor housing, and back in, so as to create a new route for the cables to sit, that wont chaff or stretch them.

I hope this helps someone.
_________________
Regards

Matt

Ex Alfa 33 'GTA' (P4 with Knobs On)
Now cruising in a 166 3.2 Ti!!

[Guest]

Hi

I have 3 speedos with dead boards, one speedo not tested yet. Still hunting for a good one.
No suitable components available from electronics stores here.

If no luck, will adapt a mechanical speedo..

TimoJ

[Matt Stolton]

Unless you can see burnt components or board, or obvious dry joints, I think the main/usual fault is the way the actual motor receives its power from the board. Having had a good mess about, I think the components look fairly hardy, it is the poor routing that was causing my problem.

My fix cures the fault of intermittent speedo, which eventually dies to nothing. I realise there may be other speedo problems, with other symptoms, but these symptoms seem to be the most common.

If you have burn outs on the boards, you have something more serious, I would guess the motor has gone short circuit, and is drawing too much current.
_________________
Regards

Matt

Ex Alfa 33 'GTA' (P4 with Knobs On)
Now cruising in a 166 3.2 Ti!!