Cluster speedometer pin help

Hello,

I've got a weird speedometer issue, its intermittent comes n goes
odometer doesnt work when speedo doesnt work
i've tried another cluster with no luck.
occasional smacks of the dash get things to work, so i assume its the pins/wiring somehow
I've tried removing the sensor with no luck, so i'd like to troubleshoot to see if the sensor is not getting power or the signal isn't getting to the cluster.
If its power, could I just splice into a switched power source and bypass the cluster?

Could someone tell me which pin is signal, power, and signal out to ecu?
Also is there a ground for the speedo sensor?  
In the image below
Green line  = signal to ecu?
Red line = pulse signal from sensor ?
Orange line = power to sensor?
or have i got it all wrong?

mick if you follow the tracks on the circuit board then look at the plug you should be able to fathom which are power / signal and earth then connect a multimeter and drive the car with clocks out.
you should then get a reading on signal wire if alls ok
if not then its more than likely a faulty diode/resistor or something in the back of the clock head

there a real pain and always going wrong.

if no signal is present then it could be a wiring fault or speedo sensor faulty