Factory Gauges Not Working

[The Rebel]

Hey All. My car is being picked up next week & hopefully will be to me by next weekend. Currently the Speedometer, Fuel Gauge & 1 other gauge works. Just wondering what the main issue you have found where the Tic-Toc-Tac, Amps, Oil Pressure... gauges are not functioning.

Is the common most issue with the gauge itself or the circuit board or perhaps something else?

On a side note just bought an orig 68 FSM off eBay for $32.10. There's another orig one for sale @ $9.99 if anyone is interested.

Thanks in advance,
Roger

 

[PurpleBeeper]

Well, at least your most important gages are working!

1. Tic-Toc-Tach - they can get old & wear out. They can be rebuilt with OEM internals or better yet, new electronic internals (still looks the same). But first, see if what you have is good. A tach needs a)power b)neg. side of coil signal c)ground wire. I think the clock is just power & ground, but I'm not sure if it used 12v battery power or 7v from the dash after the dash voltage limiter in the circuit board behind the dash.

2. Oil Press gage - with key "on" ground the wire at the sending unit. If gage, wiring & dash circuit board are all good, the gage will go "max pressure" and your problem is probably the sending unit itself. If the gage does nothing, then the problem is the gage, wire (check continuity) or circuit board (visually inspect & check continuity).

3. Ammeter - is on it's own circuit all alone. It should be getting power (through the wiring harness, bulkhead disconnect plug & dash wiring) directly from the main hot "power post with nut" at the back of the alternator. With battery disconnected, I think you can check for continuity between the gage & that alternator post/nut. The ammeter does not use the dash circuit board. It's either this hot wire, the gage itself or a ground that's your problem.

 

[The Rebel]

Thanks a million! As the car does have after market gauges under the ashtray that are working is it possible the old owner may have disconnected the factory gauges & not the tic, toc-tac?

Well, at least your most important gages are working!

1. Tic-Toc-Tach - they can get old & wear out. They can be rebuilt with OEM internals or better yet, new electronic internals (still looks the same). But first, see if what you have is good. A tach needs a)power b)neg. side of coil signal c)ground wire. I think the clock is just power & ground, but I'm not sure if it used 12v battery power or 7v from the dash after the dash voltage limiter in the circuit board behind the dash.

2. Oil Press gage - with key "on" ground the wire at the sending unit. If gage, wiring & dash circuit board are all good, the gage will go "max pressure" and your problem is probably the sending unit itself. If the gage does nothing, then the problem is the gage, wire (check continuity) or circuit board (visually inspect & check continuity).

3. Ammeter - is on it's own circuit all alone. It should be getting power (through the wiring harness, bulkhead disconnect plug & dash wiring) directly from the main hot "power post with nut" at the back of the alternator. With battery disconnected, I think you can check for continuity between the gage & that alternator post/nut. The ammeter does not use the dash circuit board. It's either this hot wire, the gage itself or a ground that's your problem.

 

[Beekeeper]

The amp gauge may have been bypassed

 

[PurpleBeeper]

The amp gauge may have been bypassed

Good point.