My tachometer is failing intermittently. Sometimes it works perfectly, sometimes it sits in one spot without moving, sometimes it very slowly reacts to changes in revs, sometimes it's both sluggish and off target. Seems to vary day to day.

Usually if it's working when the engine starts, it'll keep working for the rest of the drive/that day, and vice versa: if it's malfunctioning when it starts it stays messed up.

Any thoughts?

 

check your trailing ignitor/coil...

 

My meter was all over the place but I got about 1.3-1.6 ohms primary and 7.46k secondary for the trailing coil.

While I was at it I grabbed the lead. 1.1-1.9 primary and 10.13k secondary.

 

Nobody else has had this problem before?

 

Mine bounces if I'm over 4k Rpm's and accelerating as somthing less than WOT but it dosnt do what your saying I wish I could help but I don't know enuf to even point you in a direction with this

 

.

 

My tach will do this in the morning if it's cold out. It will have those same symptoms. It's either moisture or the solder is pulling away. Once I run the defrost for a while it works great.

 

Sticky tach - if not an electrical issue from the trailing ignitor lead - is typically due to the grease congealing on the inside of the meter which prevents smooth and easy rotation. My car does this during cold weather until it warms up inside the car.

Incidentally, that warm up cycle for passengers takes a LONG time because I soldered caps over the heater core feed and return lines. Hey, I live in the desert - we don't need heaters very often!