Tach Problem

[KIX]

On a weekend trip the tach (and only the tach) quit working. The needle would "quiver" around 1500 rpm and any engine speed. Sometimes it would "pulse" between about 1200 and 1800 at aboutte same frequency as a blinker but no blinkers would be turned on. Then it finally started working correctly for a little while. Now it's stopped working again. I feel certain it's an electrical issue.
I checked the tach connection at the dash and it seems okay. Wiggling the connection didn't seem to have any effect so I am asuming the problem is somewhere else. Anyone have any idea were the problem could be?
'02 Spartan chassis with Cummins 350 ISC. All constructive thoughts will be appreciated.

[KIX]

On a weekend trip the tach (and only the tach) quit working. The needle would "quiver" around 1500 rpm and any engine speed. Sometimes it would "pulse" between about 1200 and 1800 at aboutte same frequency as a blinker but no blinkers would be turned on. Then it finally started working correctly for a little while. Now it's stopped working again. I feel certain it's an electrical issue.
I checked the tach connection at the dash and it seems okay. Wiggling the connection didn't seem to have any effect so I am asuming the problem is somewhere else. Anyone have any idea were the problem could be?
'02 Spartan chassis with Cummins 350 ISC. All constructive thoughts will be appreciated.

[KIX]

Problem resolved. It was the tach itself. Spartan tech sefvice helped in identifying the culprit.