Bench test electronic speedometer?

[911231]

I pulled my speedometer to repair the odometer gear and it went smoothly following posts on this forum. When reinstalled it doesn't work. It has 12v at the back and I double checked the connections against a photo that I had taken. Is there a way to bench test it before I send it out to North Hollywood? I also adjusted the shift linkage and power washed the underside. I have checked the connections in the tunnel and they are ok. Other suggestions? Thanks, Al

[Autoban]

Al, what I remember working for VDO (they make these gauges for Porsche) many years ago, the pointer for the speed indication is driven by a movement while the odometers are driven by a stepper motor. Both run off the same power supply and impulse off the speed sensor. To bench test the speedometer you need special equipment to generate the pulse of the speed sensor.

1) Are they both not working anymore?
2) Did you make sure you didn't break any wires off inside of the housing?
3) Do yo know anyone with a Porsche you can swap speedos to test?

Juergen

[schumicat]

with the speedo receiving +12 volts and ground, you can touch the two sender leads (the ones in the access panel in front of rear seats) together quickly and repeat. the speedometer needle should move as you simulate the pulse of the sender. if it doesn't something is broken in the speedo or wires.

[911231]

Failed the test so I sent it off. Thank you, Al