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Speedometer Troubleshooting

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This article covers various speedometer related issues.

Common Issues Edit

Speedometer "bouncing" Edit

Sometimes the speedometer will appear to "bounce" when driving at a constant speed. "Bounce" in this context means that although the car is moving at a constant speed, the speedometer's needle seems to jump around at +/- 5 MPH or so of the current speed, never resting at any particular value.

Common causes for this problem are a binding speedometer cable, a failing angle drive, or a slipping dust cap. Often it is a gear or cable binding in the system, which in turn causes extra stress on the components and will likely result in failure of the angle drive[1].

A dust cap slipping against the wheel is the simplest to fix, in that it can simply be taped or stuck onto the hub with a mild adhesive. If the squared hole in the dust cap has become rounded, then the dust cap may be slipping against the angle drive's spindle. It may be possible to use glue or tape to make the dust cap hold the spindle better, or you can replace the dust cap with a new one from a DeLorean vendor. Note that a rounded hole may be indicative of some kind of binding elsewhere in the system.

A bad cable can be tested as per the instructions in the Speedometer Cables article. Usually the cable simply needs to be lubricated, but cables can also sometimes develop kinks or binds that limit their ability to turn smoothly. Both of these issues can put undue strain on the angle drive, eventually causing it to fail. A damaged cable should be replaced with a new one from a DeLorean vendor.

A failing angle drive implies that the entire unit is soon going to fail and will need to be rebuilt or replaced. Lubricating the angle drive may help lengthen its life and fix the bouncing problem. It is rare that an angle drive will contribute to bounce, but it common for it to fail first.

A completely failed angle drive will result in no speedometer movement at all, and the angle drive will need to be rebuilt or replaced. Usually the gearing on the drive has simply bound or failed completely, resulting in destroyed gearing and/or a snapped spindle.

Speedometer Is "Dead" Edit

A "dead" speedometer is one that doesn't seem to work at all, always staying at 0 MPH no matter how fast the car is moving. Often the speedometer itself is fine, and the problem lies with the angle drive. Sometimes the issue is the a slipping dust cap or a poorly lubricated cable, and rarely it may be the Lambda counter, but the vast majority of the time it is the angle drive.


(tip: you can buy a digital speed display)

Diagnosing Speedometer Issues Edit

The easiest way to test the speedometer system is to simulate turning the wheel by disconnecting one of the speedometer cables and chucking it into a power drill. You need to set the drill to run in reverse to turn the speedometer the correct direction.

Checking the Dust Cap Edit

The dust cap is mounted just behind the front left tire. "Dust cap" is a misnomer, as it is pivotal to the operation of the speedometer system.

Note that when removing the dust cap, a broken piece of the angle drive spindle may come out as well. This is a sign that the angle drive has seized and caused the spindle to snap, and you need a new angle drive. Be sure to check the hole in the dust cap and make sure it is still squared. If it is rounded, you will likely need a new dust cap as well.

  1. Jack up the car and remove the front left tire.
  2. Remove the dust cap. This is the yellow plastic disc in the center of the hub. Simply pull it off straight.
  3. Make sure the hole in the center of the dust cap is squared. If it is rounded, it may not be engaging the angle drive spindle properly.
  4. Test the angle drive via the instructions below.

If the angle drive works, the problem is with the dust cap. There are two common failures:

  • The dust cap may simply be slipping against the hub due to resistance from the angle drive. Use some tape, silicone sealant or other mild adhesive to stick the cap to the hub, then put the wheel back on the car and see if this helps.
  • The dust cap's square hole has become rounded to the point that it can no longer properly engaged and turn the angle drive's spindle. This may happen due to general wear, but may also be due to previously seized angle drive. Replace the dust cap with a new one from a DeLorean vendor.

See the Angle Drive article for general instructions on removing and replacing the dust cap.

Testing the Angle Drive Edit

The easiest way to test the angle drive without removing it from the car is to simulating a turning dust cap. This can be done by chucking its spindle into a power drill.

If the spindle is broken, the angle drive is likely seized and needs to be replaced. Be sure to check that the hole in the dust cap is still square and not rounded, as you may also need to replace that as well.

  1. Jack up the car and remove the front left tire.
  2. Remove the dust cap, as described above.
  3. Chuck a power drill with the angle drive spindle that passes through the center of the hub.
  4. Switch the power drill to reserve and run it.
  5. Lean into the car and read the speedometer, or have an assistant read it for you. An 800 RPM power drill at full power will run the speedometer at about 40 MPH.

If the speedometer turns, the problem may be with the dust cap. See the instructions above for checking the dust cap.

If the speedometer does not turn, test the cable from the angle drive to the Lambda unit as described [#Testing the Cable from the Angle Drive to the Speedometer | below]. If the cable is OK, replace the angle drive. See the Angle Drive article removal and installation instructions.

Testing the Lower Speedometer Cable Edit

Speedometer cables are tested without removing them from the car by using a power drill.

  1. Turn the steering wheel all the way to the right. This will provide easier access to the cable. You may find it easier to do this after removing the tire.
  2. Jack up the car and remove the front left tire.
  3. Reach behind the wheel hub. The angle drive is mounted on a large nut on the back of the hub. The speedometer cable extends from the angle drive towards the back of the car and through the firewall into the cabin.
  4. Twist the speedometer cable's connector counter-clockwise to unscrew it from the angle drive. Pliers may be of assistance here.
  5. Pull the end of the cable out and chuck it into a power drill.
  6. Run the power drill in reverse.
  7. Lean into the car and read the speedometer, or have an assistant read it for you. An 800 RPM power drill at full power will run the speedometer at about 40 MPH.

If the speedometer turns, the problem may be with the angle drive or the dust cap. See the instructions above for information on testing them.

If the speedometer cable does not work, test the Lambda unit as described Testing the Lambda Counter below. If the Lambda counter is working, replace the speedometer cable with a new one from a DeLorean vendor.

To further test the cable, you may want to remove it from the car completely and test it as per the instructions in the speedometer cables article. If it kinks or bends, replace it with a new cable from a DeLorean vendor.

Testing the Lambda Counter Edit

The Lambda counter is the yellow-ish box with an analog counter on it. It is near the near the pedals in the driver's footwell, and has with two cables and some wires connected to it. One cable runs up to the speedometer, and the other runs down to the angle drive through a hole in the firewall.

It is difficult to directly test the Lambda counter directly, as it is difficult to spin it without a cable attached to it. Instead, it is easiest to test it and the lower speedometer cable as a single unit.

  1. Disconnect the upper cable by twisting its connecter counter-clockwise. Pliers may be helpful here.
  2. Chuck the cable into a power drill.
  3. Run the power drill in reverse.
  4. Check the speedometer, or have an assistant read it for you. An 800 RPM power drill at full power will run the speedometer at about 40 MPH.

If the speedometer turns, the problem may be with the Lamda counter or the lower cable. To ensure the lower cable is OK, remove it completely from the car and and spin it by hand. The other end should spin smoothly with relatively little resistance. If it does, then the Lambda counter is bad and should be replaced with a new one from a DeLorean vendor, or bypassed completely. If it does not spin, replace the lower cable. Further tests can be found in the speedometer cables article.

Testing the Upper Speedometer Cable Edit

The upper speedometer cable extents from the Lambda counter to the speedometer.

The Lambda counter test instructions above can be used to test the upper speedometer cable and the speedometer as a single unit.

To test just the upper speedometer cable, you will need to remove it from the car. This involves disconnecting the cable from the Lambda Counter and the speedometer by removing the binnacle.

Once removed, the cable can be tested in the same way as the lower speedometer cable, as described in the speedometer cables article. If it kinks or has other issues, replace it with a new cable from a DeLorean vendor.

Testing the Speedometer Edit

The speedometer is easiest to test when it is connected to the upper speedometer cable, thus allowing it to be chucked into a power drill and spun to simulate a turning wheel. See the instructions on testing the upper speedometer cable above for how to do this.

If is working correctly and is not kinked, you may need to replace the speedometer with a new one from a DeLorean vendor.

See Also Edit

References Edit

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