tach problems...

[jwmarc]

Seems whenever it gets hot my tach starts to stick at 4k rpm.. It will operate and reflect rpm 1000-4000 but wont go past 4k.... I can sometimes flick my finger on the face and it will dislodge and fall back to idle revs... The tach gets its signal from the Coil and CDI unit.. since the car runs solid the CDI and coil are not suspect ( except for the electrical feed from the coil to the tach). What are some of the problem and fixes for the tach...BTW when the temps are in the 40-80 I dont get the problem.. When the temp is upper 80s and into the 90s it will start to happen after the car is fully warmed up.

Any thoughts would be appreciated...