Speedo Fault / Speedo Cable

[svenedin]

I am going through a list of faults that occurred whilst touring in France. The most critical were ignition faults traced to a faulty ignition switch. The second is a leak from the gearbox rear seal. The next on the list is that the speedo has packed up. The symptoms were, it started working intermittently and might start working during a drive by going from not working at all, to the needle wildly swinging around to behaving normally. This was a refurbished speedo about 2 years ago.

I tried disconnecting the speedo cable at the speedo end and reconnecting. It worked for about 5 minutes and then no needle movement. I then investigated the gearbox end of the cable. I disconnected from the gearbox and spun the inner cable around with an electric drill. The cable spun freely and easily but the speedo still registered nothing.

I am now at a bit of a loss as to what to do next. I have ordered a new cable to see if that makes any difference. The cables are not expensive. It seems to me that the square end of the inner cable is not making a good connection to the speedo drive. It almost seems as if the square part of the inner cable is too short. If I pull the inner cable out a bit and connect to the speedo, the speedo works but whilst driving this slips back and the speedo stops working.

Does anybody have any thoughts on this?

Stephen

[ManyMinors]

I had a similar experience a few years ago and found that the nylon gear wheel on the speedo drive at the gearbox end was slipping. Fitting a replacement drive cured it in my case. Might be worth a look.

[svenedin]

I had a similar experience a few years ago and found that the nylon gear wheel on the speedo drive at the gearbox end was slipping. Fitting a replacement drive cured it in my case. Might be worth a look.

OK. Thank you. Those are quite expensive and only available second hand. I'll try the cable and if that doesn't work, the next thing is the nylon speedo drive at the gearbox end. The speedo unit itself definitely does work and it isn't jammed.

Stephen

[Andmurph]

Moss have new Speedo drive pinions listed for an eye watering £106.
The are few on eBay for £20-£90

[svenedin]

The pinion and bush are available second-hand from ESM but I'll try the cable first. If it is the pinion it can be done when the gearbox is drained down to do the rear seal.

Stephen

[svenedin]

Speedo all working again with a new cable. A bit odd as there didn't seem to be anything wrong with the old cable.

I fitted the speedo end of the new cable to the speedo and then rotated the inner cable at the gearbox end with an electric drill and it all worked showing the speedo is not at fault. Then I connected the gearbox end and it seems fine on a test drive. Note: the inner cable must be rotated counter-clockwise to test the speedo and cable. Using the electric drill I realised just how fast the inner cable spins when the car is being driven. I hadn’t appreciated that.

Stephen

[mike1864]

"Note: the inner cable must be rotated counter-clockwise to test the speedo and cable."
Never drive it clockwise. I did that once; and ended up in 1973

[svenedin]

Longer test drive today and speedo is working well. Of note, with a new speedo cable the speedo is incredibly well behaved and doesn't do any wild swings at all.

Stephen