tach is acting up

[lukedukem]

not sure if this belongs in the electrical threads but heres a video of my tach. i stating in another thread i was having issues and posted a video to see if any of you guys might know why it was doint his.
first it is reading high. i have 3.23 gears and the rpms at 60 read above 3k, which says i have 4.10 gears, but thats wrong. so theen it jumps around... just please watch video and see what yall think in the video i'm crusing at 60mph, no change at all

https://www.youtube.com/watch?v=ElF0_xqXXDU

luke

[mhinders]

I had a similar problem with bouncing tach. In my car the problem was bad grounding of the tach/instrument cluster.

[justcruisin]

You need to check your ground and power supply to the tach, also check the wiring for the signal, distributor tight and ecu grounded properly. If all OK it is probably the components on your tach board failing. There are some capacitors that dry up and give trouble. Give Brent at Mr Heaterbox a ring and he will hook you up with a new board, tell him what ignition system you are running.

[68r/t]

Mine started to do the same thing, I could be at idle and the tach would start to flash  to 4000 or so rpm, and when driving it did also .
Mine ended up being the fbo ignition box, I put a spare orange  box that I had in and it stopped doing it and went back to normal.

[GF7Bee]

Mine was doing the same thing and it turned out to be a bad coil.

[lukedukem]

if ti was the coil would it cause the car to run bad... my car still runs great. no issues at all.

luke

[firefighter3931]

If you have a multi-spark box that will certainly affect the tach function. Most aftermarket boxes deliver multiple sparks below 3000 rpm. 



Ron

[lukedukem]

If you have a multi-spark box that will certainly affect the tach function. Most aftermarket boxes deliver multiple sparks below 3000 rpm. 



Ron

i'm lost now. how do i know if i have a multi-spark box. i have the orange box under my hood is that it

luke

[firefighter3931]

If you have a multi-spark box that will certainly affect the tach function. Most aftermarket boxes deliver multiple sparks below 3000 rpm. 



Ron

i'm lost now. how do i know if i have a multi-spark box. i have the orange box under my hood is that it

luke

MSD, Mallory, Crane etc....are multi spark ignition boxes. 

The factory style orange/black/chrome boxes are single fire 

The issue with your tach is most likely non-ignition related. The tach itself is the problem.



Ron