Speed Sensor AC Voltages

Hi, Can you help with the speed sensor AC Voltage.

Symptoms, at idle the speedo will flicker 0 to 100 Km/h approx and when driven the speedo reads 185km/h (full scale) and occasionally it will read correctly then go faulty again.

Disconnecting the Speedo Sensor I get the following AC Voltage Results;

339mV (0.3VAC) when removed from the vehicle and spun clockwise as fast as I can manual spin.

NB: the manual says 0.5V AC approx

3.69V AC approx at 50Km/h

4V AC at 60 Km/h

5V AC at 80 Km/h

If this is correct then I will have to investigate the Instrument Panel which visually appears Ok.

Thanking you,

Ronald with the 1991 GQ Nissan Patrol 4.2D

Quote:

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Originally Posted by Ronald

Hi, Can you help with the speed sensor AC Voltage.

Symptoms, at idle the speedo will flicker 0 to 100 Km/h approx and when driven the speedo reads 185km/h (full scale) and occasionally it will read correctly then go faulty again.

Disconnecting the Speedo Sensor I get the following AC Voltage Results;

339mV (0.3VAC) when removed from the vehicle and spun clockwise as fast as I can manual spin.

NB: the manual says 0.5V AC approx

3.69V AC approx at 50Km/h

4V AC at 60 Km/h

5V AC at 80 Km/h

If this is correct then I will have to investigate the Instrument Panel which visually appears Ok.

Thanking you,

Ronald with the 1991 GQ Nissan Patrol 4.2D

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That sounds about right.

If the other readings were taken with the vehicle running up on blocks and the rear wheels free spinning that would explain the high readings.

Your problem is more then likely a dry solder joint on the back of the speedo head.

With a soldering iron redo all the connections on the circuit board for the speedo head and connector.

I also remember reading a post about a loose capacitor in the circuit board so check for this and re-solder.