Speedometer failure is likely to be caused by a fault in the cable that runs from the gearbox to the back of the speedometer gauge. The speedometer cable is driven fromIWC Replica Watches
the gearbox, and curves smoothly up through the engine compartment and the bulkhead to connect with the back of the speedometer.
If the gauge needle does not move at all, the inner cable or drive may be broken; or the cable’s square ends may have become rounded with wear and fail to engage in the sockets.
The fixings at the ends can work loose or be wrongly fitted.
If the gauge needle swings or moves sluggishly, gearbox oil may have seeped up the cable and got into the speedometer itself. In that case, you must replace the speedometer.
If the needle twitches rapidly, see whether the cable is crushed, kinked or too sharply bent. Intermittent twitches can be caused by loose connections or by worn and slipping ends on the cable.
A tapping noise is a sign of a damaged drive or lack of lubrication.
To examine the cable for any of these faults, support the car securely on axle stands or ramps.
Disconnecting and checking the cable
Disconnect the cable from the speedometer and check for loose fittings and worn drive ends.
First look over the whole length of the outer cable to see if the casing is broken anywhere.
Make sure that the cable follows a smoothly curved route and is not kinked or crushed. There should be no bend within 50mm of either end. Bends elsewhere should have a radius of not less than 150mm.
On some cars, guide clips hold the cable in place. Make sure that it has not worked loose.
The cable is connected to the gearbox by a knurled thimble nut, a circlip, or a forked plate.
Unscrew a thimble nut with your fingers, starting it with large grips if necessary. Squeeze a circlip free with circlip pliers.
A single screw holds a forked retaining plate. Unscrew it.
The top end of the cable is harder to reach. If you cannot reach it, remove the speedometer or the instrument panel.
The top connection is a knurled thimble nut, or one of several types of clip. Most clips release when they are pushed in and turned sideways; one type has a ribbed area on one side, which you depress to release the clip.
Examine the square ends of the drive for wear and check that the fixings are sound.
Turn one end of the drive by hand while a helper watches the other end. If the other end does not turn, the drive is broken. If the drive turns stiffly or you feel it snagging, check that it is not kinked or crushed by a sharp bend or a guide clip.
If one end of the drive moves in a circle instead of revolving on the spot, the drive is kinked.
If the drive seems undamaged but is generally stiff, it may need lubrication.
Pull the drive out of the casing, clean the drive with petrol, smear it sparingly with grease and slide it back.
Some inner cables, however, have captive ends and you cannot pull them out. In that case, feed light oil between the cable and outer sheath.