tictocTACH problems

So i have a 68 Coronet rt. Tach was reading way to much since i have it. But nowadays if i drive over 3000 rpm (aftermarket tach) the original tach is fully engaged to the bottom right side. Thats kind of scary, dont want to burn the dash. Also noticed that the clock acting weird. Sometimes it does nothing, runs too fast or just works. Could it be the 5 volt limiter? Dont really know where to start...

Electrical ignition, revnnatorbox + coil.

Thanks for ur input

I need more data to give a better opinion BUT, to me it almost sounds like a bad ground?
Do you have a Fluke Style multi-meter?
Get yourself one of these in e PIC below from Harbor freight
That way you can:
A) Turn on the ignition, check clock performance
B) Voltage readings with just ignition "on"
C) Start engine, take voltage readings on terminal to tach
D) REV engine, voltage readings
It could be a BAD tach
Remember: A bad alternator or Voltage regulator can also cause the tach to act crazy!
Check your system Voltage with a digital multimeter with a fresh battery at idle, 2000 rpm, 4000 rpm, and compare the readings to another vehicle.
Above idle the system Voltage should be between 13.5 Volts to 14.5 Volts, and should be steady, not fluctuating

Could be rev-box needs a filter added.

I'm going to guess you haven't installed the electronic tach board to go along with the ignition?

Lionized said:

I'm going to guess you haven't installed the electronic tach board to go along with the ignition?

Click to expand...

whats that?

super-bee_ski said:

I need more data to give a better opinion BUT, to me it almost sounds like a bad ground?
Do you have a Fluke Style multi-meter?
Get yourself one of these in e PIC below from Harbor freight
That way you can:
A) Turn on the ignition, check clock performance
B) Voltage readings with just ignition "on"
C) Start engine, take voltage readings on terminal to tach
D) REV engine, voltage readings
It could be a BAD tach
Remember: A bad alternator or Voltage regulator can also cause the tach to act crazy!
Check your system Voltage with a digital multimeter with a fresh battery at idle, 2000 rpm, 4000 rpm, and compare the readings to another vehicle.
Above idle the system Voltage should be between 13.5 Volts to 14.5 Volts, and should be steady, not fluctuating


View attachment 529196

Click to expand...

i have and i´ll do. Will post what i got....

BeavisHQV said:

whats that?

Click to expand...

I would check everything else first but this is what I have installed. Pretty simple to do yourself if you're handy with a soldering iron.

http://rt-eng.com/rte/index.php/RTE_67-74_Tach_kit