When I purchased the Dart four years ago it came equipped with a non-working 20 year old Super Pro Tachometer; it had been disconnected at some point. During the initial rewiring to get car back on the road I reconnected it with new conductors & connectors, and it has worked since.

Recently it would drop off showing about half actual rpm, and then bounce back to realistic reading. Yesterday it appears to have slipped into a permanent state of incorrect rpm indication. Yesterday this malaise seemed to be activated occasionally by a bump in the road, bit no amount of juggling wires would cause it to return to reality, but instead it would heal its self while driving. After a few miles of driving it slipped into a permanent state of mental illness of "correct over two" readings.

I checked position of 4, 6, 8 cylinder setting switch, it was set on 6. Switching between 4, 6, and 8, produced little change in reading.

I checked the red 12v supply, and it is consistent with battery voltage, no voltage drop on black ground wire, gage illumination works as designed. This leaves the green signal conductor from coil untested.

Coil end of green wire voltage was around 4.5 v if I recall correctly, but I should revisit this number. I did not check signal voltage at end of tac’s pigtail.

Any ideas as to what has happened to this device, or is thing DOA?

Bill

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Intermittent connection inside tach.

Might be at solder connection.


Can you take it apart?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

[quote]Can you take it apart?[/quote]



I don’t know if it will come apart willingly. The circuit board is located in plain sight once rear cover of gage is slid off, however all of board’s solder joints are not in view.

I’ll investigate later in week when “allâ€￾ steering coupler parts arrive and the steering wheel is removed where tachometer is mounted on steering column. Steer N Gear did not ship the full rebuild kit I ordered.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I inspected both sides of the tachometer’s circuitry, and found no suspect solder connections, or lose conductors. Short of reheating each joint I don’t know what else to do. I checked continuity of all four conductors to the circuit board, they all rang out. Electronics ain’t my bag baby. Maybe a capacitor is beginning to crap out.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

The only way to know for sure. But dont use the hd trigger syled soldering 'gun', use a lower wattage 'pencil' iron. (cheapy from RS or HF will work)

Its a possibility, but sounds more like a bad/cold solder joint.

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MRO....

Cheap, Fast, Reliable.... Pick 2...

I have grown tired of screwing with this old tachometer that came with the car, it is probably 20 years old, and been living in a less than desirable environment that old convertibles generally provide for electronics. It had to be coaxed into working four years ago when I got the car on the road, so I replaced it today.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC