speedometer sensor

[70racing]

I recently removed and replaced engine and xmission - reconnected speedo wires and now no speedo or odometer - worked fine before, coincidence or do I need a new sensor? Thanks as always for advice. It's an 85 911.

[Flat6pac]

If you plugged in both wires, it should be powered. One could ground out if you didnt use the square block to plug into.
Bruce

[E Sully]

Disconnect the 2 wires from the sending unit, put a continuity tester on them. Raise the rear of the car and rotate one of the wheels. You should see a pulse on the meter as the magnetic pick ups rotate in the transmission. You could also check to make sure the speedometer is getting 12v when the key is on. Top terminal labled + on the speedometer. Sensor is connected to bottom terminals labled 31b and -.

[Wil Ferch]

I've seen the sensor *not* work for 0-5 mph, or 0-20 mph... at which time the speedo "jumps" to the correct speed and then continues reading correctly for any higher speed. Keep this in mind as you trouble-shooot this area by hand-rotating the wheels.

[70racing]

Thanks for all suggestions - will put it up in air tomorrow and do these checks and report back -