Speedo: test output of "pulse generator, speedometer"

[Gene in NC]

Speedo: test output of "pulse generator, speedometer" (PGS) (official realoem term)? What is the test point/location and what type tester is required to check if speedo/cluster is recieving signal?

Original cluster speedo failed, followed by tach a few minutes later (15/20 min). Temp gauge and service computer had not been operational.

Following cleaning of fuse contacts the original cluster would show aprox 1/2 of actual at speed, ie 35mph and 1,200 rpm at 70 mph actual. Seems like power or ground. Ground at chassis for cluster serviced.

Trying "known good" cluster (no temp gauge, etc.) but good speedo and tach. Tach reads accurately but speedo "0".

[winfred]

id check the speed sensor at the diff it's easyly checked with a multimeter set to diode, it's not a ac generator like most speed sensors it's a switch