Tach Issue has me puzzled. HELP!

[ss427copo]

Yo Gentlemen....
So, I take the instument cluster out of the 67 Impala Big Car to replace the clock. All goes relatively easy. It goes back together, the clock starts ticking like it should..BUT then the tach starts acting goofy. It worked perfect before. The sweep hand did get moved when it was out of the car (i used low, low pressure air to remove the 40 years of dust, but did not point the air at the tach's pointer) It went back in at about 200 RPM's, only moved to 2000 when I rev'ed it. Now it settles at 3000 like it should be at 0?? Any ideas?

Jeff