Tuesday, March 22, 2011

Sensor location and available reference voltage


1. Location of speed sensor harness plug, push the retaining clip to remove.

2. White/Red wire is 12 volts.

3. With Positive volt meter lead, probe the back side of the connector and NOT the wire insulation.
    Note: .035 mig weld wire was used to probe connector. 

      Note: Removal of speed sensor plug is not necessary for this test.

4. Reinstall speed sensor plug if you removed it.

5. It will be necessary to install a alligator clip lead from negative battery post to make the ground accessible with the weighted seat down to engage the seat switch (illustrated below, not shown in video). 

Weighted seat down in the operating position with negative leads attached (illustrated below)

6. Ground lead from voltage meter to negative battery terminal. Any and all BATTERY voltage tests should
    be grounded to the negative battery terminal as illustrated to ensure proper test results.

7. Key on

8. Voltage meter should read 12 DC battery volts minimum.

1.  The green lead is signal to controller voltage and will vary with the wheel motor speed.

2.  Voltage shown is approximate, if the voltage varies as the speed control lever is moved the sensor is
      probably operating correctly. Note that the voltages I was getting were not a smooth steady increase.

3.  When probing the green wire you are also checking the plug connections. If there is no
      voltage at  the green wire terminal, it may be a speed sensor failure or it may be a poor spade connection.  

4.  Notice the voltage shows in both the forward and reverse speed control lever positions.

5.  The white/green lead is also signal to controller voltage and all statements concerning the green lead will
     also apply here.

6.  The white/black lead is the sensor ground. Resistance should be zero between the lead and the negative
     battery terminal. The slight resistance shown here is from internal circuitry. Resistance is tested in ohms
     with electrical circuits off.

Testing a defective speed sensor
   1. A defective sensor will usually produce a 4A31 code. As of spring 2011 the most common cause of
       speed sensor failure has been metal sticking to the sensor from the failure of an internal thrust washer.
       If this is the case the entire electric wheel drive which includes the sensor needs to be replaced.

       A defective sensor will will also produce unpredictable variable voltages when the control arms are
        moved to the drive position. The neutral position may still show 12 reference volts . The illustration
        below shows a speed sensor that has metal particles attached from a thrust washer failure. Compare    
        these voltage results to the sensor test voltages above. The properly functioning system will show 12V
        as the controls are moved inward from the brake position and will immediately drop to 6 volts when
        the controls are moved forward or reverse. As the controls are pushed further into the driving positions
        the voltages will steadily increase or decrease as the controls are moved forward or backward.

 If you determine that the electric drive motor needs to be changed, refer to the illustrations 
      below for removal.
         1. Remove the speed sensor plug.

    2.  Remove electric drive mounting bolts.

    3.  Remove the rear electric drive guard.

    4.  Remove the large gauge electric cables noting their position, as well as the remaining two harness

    5.  Illustration below shows an electric drive operating properly as shown on the unit display and the
         volt meter. 


Safety brake failure
        Brake failed in the locked position (we saw on unit with this issue)
  1. Code 02A13 showing on display
  2. Verify that the controller or harness is not at fault by installing the electrical park brake release
  3. If the side in question will not roll easily and the opposite side does, replace the electrical traction drive unit.