Once the speedometer cable breaks, the gauge will not tell you the accurate speed of your vehicle. The needle on the speedometer might bounce or fluctuate or fail to give you any sort of reading. If the speedometer gear or speedometer itself is working, then the cable may be the real problem. To check, here's what you can do:
- See if the speedometer gear is working fine. Pull out the gear by unscrewing the bolts and the flat piece of steel. See if the gear has any sign of damage or some missing teeth. To test the gear, spin it by hand. If it won't rotate easily, then chances are you have a locked-up speedometer or a broken cable.
- Unscrew the cap to separate the cable from the gear. After removing the gear, check the cable end on the side of the gear to see if this is still intact and square. Spin the gear while someone else keeps a close watch at the speedometer. You have a bad gear if the speedometer jumps or bounces as you spin the gear by hand.
If after some tests and inspection, you've found out that you have a bad speedometer cable, then this should be replaced.
Replacing the old cable
Step 1: Pull out the cable from the gear. You have to undo the clamps that secure the cable to the body underneath the car. You also have to remove the dash cover on the front of the instrument panel. After removing the screws, pry off the cover from the dash using a screwdriver. Make sure that the electrical connectors have been detached before you remove the cover. Finally, undo the screws that secure the speedometer pod to the dashboard.
Step 2: Trace where the speedometer cable goes, going along the path of the firewall that's near the steering column. You have to pop the hood for this. The cable has a rubber grommet that fills in the firewall hole, where the cable goes. With a long screwdriver, the grommet should be pushed through the firewall and into the inside of the car. As you do this, you have to fetch the cable from inside the car. This cable is underneath the dashboard. Remove the grommet from the cable with a wire cutter. The loose speedometer cable will then come out along with the speedometer. You have to pull out the speedometer carefully before you can undo the cable. You may have to make sure that the electrical connector is unplugged.
Step 3: For cables with a squeeze-type lock, pull out the cable by squeezing the top and bottom parts of the clamp. For cables with a screw cap on the gear, you'll have to pull out the cable from underneath the hood.
Step 4: Insert the speedometer cable through the firewall. Start with the engine side. Inside the car, you have to pull it in and stretch this till it reaches the grommet. The grommet should then be pushed into the hole. The next thing you have to do is push the cable into the speedometer. You have to pull back the cable and turn it if it can't be inserted easily. Do this until the square end is lined up and the cable is able to go in.
Step 5: For the squeeze type, slide in the cable until the retainer clicks into place. For the screw type, the cable should be secured with the screw. After this, you have to put back the pod and dash cover. The speedometer cable should then be attached into the brackets that held it. The end of the cable should go into the speedometer gear. You'll have to turn or rotate the cable so that it will go in. Finally, you have to tighten the screw cap.