erratic inductive tach..need coax wire?

[Sinkingfast]

Both my tinytach and my hardline tach are all over the place. The first tinytach I had used a coax wire with a grounded shield. That one was fine. The last tiny and hardline do not use the coax wire. I have read about others with the same erratic issues. I am going to replace the wire on my hardline tach with coax and i will report how it works.

Any other suggestions?

 

[Al U Minium]

Routing of the wire near a high signal noise source; ignition, transducer, radio transmit antenna, can induce unwanted signals into the tachometer device.
1. The pickup sensor must be properly mounted
2. Route the sensor wires away from noise sources, do not run parallel with other wires
3. Coax may help but the first two mentioned are the most critical
4. The device you are using is defective