2CV SPEEDOMETER CABLE
If your speedometer isn't working the problem is probably a broken cable. If the odometer is still working then it isn't a broken cable, the speedo will need to be repaired or replaced. Disconnect the battery first as you will be delving amongst all the wiring on the back of the instrument panel.

When you have freed the instrument panel pull it towards you, taking care not to disconnect any of the wiring, and unscrew the plastic sleeve which holds the speedo cable in the speedo. You can now check to see if the cable is broken or whether the non-functioning speedo is caused by something else. Pull on the squared end of the inner cable. If it pulls out, the cable is broken; if not you will have to look elswehere for the fault.
Working under the parcel shelf locate and remove the rubber grommet through which the speedo cable passes to the back of the instrument panel. The grommet probably also carries the brake light wiring to the pedal switch. You can now pull the end of the speedo cable through the hole and then pull it out of the grommet taking care not to damage the brake light wiring which will remain in the grommet.

Under the bonnet locate where the speedo cable enters the back of the gearbox. Look for an 11mm bolt just below the cable, clean it off and remove it. The gearbox end of the cable can now be pulled out of the gearbox - take care that the plastic gear housing doesn't come out as well - if it does, push it back in immediately. The end of the speedo cable can now be pushed through the bulkhead into the car. There should be a foam sleeve where the cable passes through the bulkhead which is split along its length so that it can be removed from the cable and reused on the new one.
To ensure that the speedo needle doesn't flicker make sure the cable has no tight bends or kinks throughout its run from the gearbox to the speedo. Also make sure that it can't come into contact with any moving parts (such as heater controls) or sources of heat (such as the exhaust or heat exchangers). Reconnect the battery and go for a test drive!
Before fitting the new cable it's worth checking to see whether the instrument is seized which would have caused the cable to break in the first place. Insert a small screwdriver, about the same size as the squared end of the cable, into the back of the speedo head and turn it in the same direction as the speedo needle would go (anticlockwise as you look at the back of the instrument). If the needle doesn't flicker or you can't turn the screwdriver at all the chances are it's seized and will need repair or replacement.

To fit the new speedo cable start inside the car. Push the gearbox end of the cable through the bulkhead, remembering to replace its foam sleeve where it passes through the bulkhead. Locate the cable into the gearbox - you may have to turn it a fraction at a time to locate it fully in the drive. Replace the 11mm bolt which retains the cable in the gearbox. This can be quite fiddly. The bolt passes through a narrowed section on the metal sleeve of the cable (see photo) and you may have to withdraw the cable slightly, or push it further into the gearbox, to the point where the bolt will go in and line up with its thread in the gearbox casing. Tighten the bolt.

Inside the car push the instrument end of the cable through the rubber grommet and then push the cable through the hole in the parcel shelf just far enough to reach the back of the instrument. Locate the squared end of the cable into the speedo until the metal sleeve is a snug fit against the instrument and screw on the plastic sleeve. Remember to relocate the rubber grommet in the hole and make sure you haven't inadvertently disconnected any wiring.
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It's necessary to remove the instrument panel to replace the cable (dealt with elsewhere on this website).
THE WESSEX DUCKS
THE WESSEX DUCKS
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