98 Civic DX Testing Speedometer and VSS

[DFS]

I have a 98 Civic DX (5spd manual trans) with an erratic acting speedometer. It may act normal at startup, it may set static at 20 or 40 when the car is started, or it pulse wildly between 40-60 as the engine cranrk over.

The question I have is what voltage reading should be at the Speedometer connection if the ignition is just turned to on (run but not started) and the car is not moving?

What I have done so far, much at suggestions I found in other threads. Thank you to everyone.

• removed the VSS connector and checked the volatge to the VSS (ground to 12v input = 11.82v)
• removed the VSS and checked to broken drive. Appeard to be fine
• removed the instrument cluster and checked voltage of VSS input wire (blue/white)
  • ignition (ign) on, turning VSS with fingers = .03 to 4.5v
  • ign on (VSS reinstalled) pushing car slowly = .03 to 4.5v
• reinstalled cluster and test drove. worked fine for about 1/2 mile, then dropped from 35mph to 20 and hung there.

Back to the garage for more testing

• pulled the cluster again, with the ign on (but not started) =4.52v... if the shouldn't this read 0?
• also in another test I disconnected the VSS and checked voltage at the speedo and it read 4.52v

Speedo head, VSs or wiring. Anyone have any idea?

[DFS]

Update:

After a bit of digging I found the info to verify the speedo head was bad. The voltage to the speedo head is based on the position of the sensor, not the movement of the sensor coil past the pickup. So if the coil is clear of the pickup the reading is '0'. If the coil is fully in front of the pickup the reading is 4.5 to 5 volts. If the coil is stopped in front of the pickup, you will see 4.5 (5) volts with the key on and the sensor not moving. I thought this was indicating a short in the wiring, but it is the normal condition.

Picked up a used cluster from the auto graveyard and under 7 minutes cluster was changed out and operating properly.