Tach issues...

[bugnut68]

Bouncing needle and flickering shift light on occasion: what would cause this?  I installed a used Auto Meter shift light tach and am having some issues, despite having it wired up completedly correctly.  One would think perhaps it's a bad ground, but this doesn't appear to be a factor in my case.  I am just wondering what I should look for.

The wire going back to the coil is in pretty close proximity to the coil wire, would this cause any type of interference or incidental signals that the tach may pick up?

[Zach Gomulka]

Yep, keep the tach wire clear of any plug leads.

[bugnut68]

Yep, keep the tach wire clear of any plug leads.

I'll have to crimp an extension and get it clear of that coil wire... I'm almost positive that's the issue after mulling it over a while...

[Dustin]

Are you running pointless ignition?

I am running the Compu-Fire and had that issue flare up after working fine for a while. After trying another tach and having the same problem, I checked the module and discovered that it was ever-so-slightly loose. Tightened it up and solved the problem.

Good Luck!
Dustin

[bugnut68]

Are you running pointless ignition?

I am running the Compu-Fire and had that issue flare up after working fine for a while. After trying another tach and having the same problem, I checked the module and discovered that it was ever-so-slightly loose. Tightened it up and solved the problem.

Good Luck!
Dustin

Actually, I do have a Compufire or Pertronix (can't remember which , I've had both, think the Pertronix went with my '68 went I sold it) in the 009, so I will check that out.  Appreciate the tip!

[Dustin]

Try to wiggle the pickup. The bolt felt tight but I could still move the pickup barely.

[Jason Foster]

I agree with Dustin the pickup has to be firmly grounded to its mounting point. Whether its in the distributor or on a crank trigger mount.

[bugnut68]

As an update, I'm pretty sure the Compufire module gave up the ghost this weekend.  Engine stopped dead and wouldn't restart during time trials, and a later check revealed no spark.  I'm fairly certain it's not the coil, as the coil is only about 5K miles old, and the distributor has wayyyyyyyy more than that on it (the Compufire too, as it used to be in my old '68 daily driver for two engines and tens of thousands of miles).  Perhaps the tach was giving me an erratic warning my ignition was about to go?  Better at the track than on the highway somewhere, I reckon.

[Dustin]

Bummer!

 I bought the "off brand" module the first time and it only lasted about 5000 mi.

Guess I got what I paid for!

[bugnut68]

As an update, putting in points and condenser did nothing... appears my coil is shot.  And it's only 5K miles old, but it has been exposed to four extremely cold Lake County winters (often dipping below the zero mark, snow, etc)... perhaps that hastened its demise?  No spark is the bottom line, and I'm wondering if the coil's condition may have had a role in my tach's erratic behavior.

[bugnut68]

Tach is the issue... disconnected it and the car runs fine now.  An attempt to resolve the issue with the seller resulted in a nice, rude response.  I'm pretty well set on never buying a used tach ever again.