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Tachometer
#1
Just can't stay away
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55packard400
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Hello
I have noticed inthe forum some photos of
Members cars that have a tachometer mounted
Can anyone tell me how to connect a conventional tach
Which is 12volt negative ground to our positive ground system
Thanks
Mark

Posted on: 2018/2/14 11:13
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Re: Tachometer
#2
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Craig Hendrickson
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They do sell polarity reversers, but it's been a while since I looked that up.

Or, you can do what I did on my 55 Pat, change to Neg ground like the 56s. It's easy. The T-L, ignition, lights, most gauges, AM radio and starter don't care. Only the ammeter, regulator and generator care. You can buy a neg ground regulator like used on the 56s and change the terminal connections on the ammeter and generator. This change also makes it possible to install a modern neg ground AM/FM/CD for better sounds.

Posted on: 2018/2/14 14:06
Nuke them from orbit, it's the only way to be sure! Ellen Ripley "Aliens"
Time flies like an arrow. Frui
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Re: Tachometer
#3
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HH56
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You can buy a neg ground regulator like used on the 56s and change the terminal connections on the ammeter and generator.

No wiring changes needed on the generator but it must be repolarized if changing the ground polarity. Instructions are in the SM for that procedure. Possibly Craig meant change the terminal connections on the ammeter and coil instead.

The only other items that would care is if you have a modern solid state replacement for an original item. The radio vibrator replacements and some of the solid state torsion level control switch conversions do care.

Posted on: 2018/2/14 14:16
Howard
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Re: Tachometer
#4
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PackardV8
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I'm not 100% sure this will work:

Run the ground wire for tach directly to + post of battery.

Run power wire for tack directly to - post of battery.

Then connect tach wires to ignition coil.

Seems like i tried this some 6 or 7 years ago on a SIX volt + grnd system and it worked just fine. The tach is a SUN tach, 12v about 20 or 25 years old. The tach did't care that it only got 6 volts and i think i just wired the power wires to Battery directly as stated above.

Posted on: 2018/2/14 15:44
VAPOR LOCK demystified: See paragraph SEVEN of PMCC documentaion as listed in post #11 of the following thread:f
http://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=7245
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Re: Tachometer
#5
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HH56
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Keith's idea may work but for that approach you need a tach with two power wires and not the typical 1 wire with the case providing the other connection. It also needs an inductive sensing rather than a direct connection to a coil lead and an incandescent bulb for the dial. If you have one with separate wires verify neither of the pos and neg power are directly connected to the case or else make very sure that the tach mounting and case is isolated from dash metal when it is mounted. If a power wire is common to the case and was hooked up to an opposite polarity battery connection then you would have a direct short when the case was mounted and it touched a regular ground.

If you do not have a dual power wire unit but still one with an inductive sense it may still be able to be used by mounting the tach in a plastic housing attached to the dash. With the tach isolated from a regular grounded surface run a wire to the tach case and connect that to a switched source and use the regular power lead to connect to ground.. Modern units with an incandescent bulb illuminating the dial should work but one with an LED may not since there is probably no way to change the LED or isolate it from the rest of the circuitry.

Posted on: 2018/2/14 16:00
Howard
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