Been having a real tough time getting an Auto Meter tach to work in my '65 with a 289. Engine has been converted to an '85 Ford Duraspark ignition, with a '95 TFI-style coil (the type that looks like a little square transformer). Tach was hooked up according to instructions...but would only read about 1/2 actual rpm. Called Auto Meter...they told me to switch tach wire from the GREEN wire on ignition module to the ORANGE wire...did so...same result. Called Auto Meter....they told me to send tach back for replacement...did so...received new tach and reconnected according to their instructions...SAME results. At about 1,000 rpm, tach shows about 400-500, and as you increase rpm, needle actually drops a bit before climbing. Never reads more than half of actual rpm....and I have run enough 289 and 302 engines to know more or less what rpm they're turning. Any ideas...???

 

Huh...that's odd. Never heard of that.

It has been a while since I've hooked up one of those tachs but as I recall:

Red-hot
Black-ground
Green-negative side of the coil
Blue- lights


How's your ground?

Is this one of those adjustable tachs that read for 4-6-8 cylinders?

What kind of wire are you using? It's not resistor wire is it? Just a shot in the dark...

 

Yeah, it's hooked up according to instructions. Ground is good...connected straight to intake manifold. Light works on tach. The tach engine cylinder adjustment option is not it, either. With a V-8, anything other than the correct setting would make the tach read HIGHER, not lower, than actual rpm. Guess I'll call Auto Meter one more time and ask why they told me to connect to the orange ignition module wire, when everything I've read says to use the green. Wondering if the "mix and match" ignition system I have is part of problem. Can't see a voltage regulator on the alternator, but one must be there, as the OEM external reg. is disconnected and engine still runs ok and battery charges. On this note...the guy at the auto-electric shop where I had my tail-lights and turn signals rewired told me that the alternator is actually for a Chevy...!! Previous owner did some really weird stuff to this car....!

 

Unscrewing "custom" wiring is a hoot.

 

You got that right! And the wiring is the easy (cheap!) part...the PO also put front disc brakes on it using mid-90's Mustang REAR rotors and Oldsmobile calibers...which he WELDED to the front spindles!!! I could go on..but I won't. But hey...seriously...on that voltage regulator...don't know why it's not connected. The wiring harness for it is taped up...so not like someone just "forgot" to plug it in.The alternator is a Delco-Remy...maybe has an internal regulator?

 

Yes Delco Remy alts from the 70's have an internal Vreg with a small 2 wire plug inserted from the side used to excite it. Don't plug the Ford reg back in