Volvo: 1986 volvo dl speedometer, speedo sensor, spade connectors

Question
Is there any way to test the speedometer and transmission sensor to determine if they are defective? My odometer and speedometer are not working. I replaced the gears but the motor is not turning. I have power to the speedometer head. With the power off the speedometer reads 0 MPH and when the power is turned on the speedometer jumps to 40 MPH and stays there or may increase a bit as I drive. Also need to know correct wire hookup. On the back lower side are two spade connector one male (right side looking at back) and one female. (left side looking at back). On the right of the speedometer when looking at the back are two connected male spade connectors. What color wire go the these connections. Not sure if speedometer is bad or sender on transmission are bad. Thanks for our help. Allan

Answer
Allan
Volvo has a tester that hooks to the wires in the trunk and power the speedo. Speedo repair shop also are able to run the speedo. If you hook up to the wires from the speedo sensor and spin the wheels you should get an AC signal/waveform. On the doublw male wire connector goes the yellow wire from the cruise control. On the smaller terminal lower side left of sppedo should be the overdrive wire yellow/red.