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Discussion Starter #1
65 289. Bought a 4 wire tach and have a question. No problem with white (illumination), black (ground) or green (coil). The power wire (red) is, according to the directions, supposed to be connected to a source that is hot when the key is in the on position and off when the key is in the off position. I had plans to use the cigarette lighter but have found out that that is always hot regardless of the ignition key position. Seems like I read somewhere that the threaded stud sticking out of the back of the ignition switch would work (I don't know that for sure) but that is a bear and a half to get to for this fast approaching the age of 80 old fart. I am neither agile nor spry.

Do any of you have an idea of a source or wire that isn't so hard to access that fits the above description? If it is somewhere under the hood, that would be ok too.

Thanks in advance.

Chuck Sarsfield
Ft Myers, FL
 

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Try the accessory out side of the accy fuse at the top of the fuse box. I believe in some early models there is a wire from the right side of this fuse that goes to a 3 plug female specifically for adding accessories.
 

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Try the accessory out side of the accy fuse at the top of the fuse box. I believe in some early models there is a wire from the right side of this fuse that goes to a 3 plug female specifically for adding accessories.
Thanks, but my fuse box doesn't seem to have an accessory site as you describe.
 

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Tap into the output side of a key on accessory fuse - the radio springs to mind.
I personally would avoid things with motors like the wipers and heater.
 

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Tap into the output side of a key on accessory fuse - the radio springs to mind.
I personally would avoid things with motors like the wipers and heater.
I rarely feel as stupid as I do when I ask a question on this forum. Your advice to "Tap into the output side of a key on accessory fuse..." is no doubt spot on great advice but I have no idea what it means.
 

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'Key on' fuses will have power on only one side when the key is off. Locate one (like the radio fuse) and use a test light or volt meter to determine which side powers on and off with the key. That is the side you should connect your tach power line to. You should be able to get a (glass) fuse tap from any shop that does auto stereos, alarms, etc.



Another less attractive alternative is to locate the power wire going to the radio and tap into it.
 
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A test light is your best friend. Own it, cherish it.
 
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The center post (accessory) on the back of your ignition switch is a switched 12 volt source and not really more difficult to access than the other suggestions made here.
 

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Tools, tools, tools, Buy'm! They will be your helper for many years!
A minimum arsenal should consist of ...
1. Volt meter aka "VOM"
2. Timing light w/RPM readout
3. Vacuum gauge aka (VAC gauge)
4. Feeler gauges (points, plugs etc)
5. Dwell meter (if one can still find them for Points)
6. Probe type test light (one end has alligator clip the other, a probe point (think ice pick) with a built-in test light)
7. Remote starter switch
Just to name a few...
 

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Here's a photo of my 66 fuse block. Yours should be very close. The upper fuse is marked accy for accessories. You can slide a female crimp-on connector between the fuse clamp and the body of the block. Another option is to look under the dash and follow your radio wire back to the place it connects into a harness and see if there is a 2 or 3 hole connector. These are all key-on points.
 

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The most common method is...
Assuming you have a stock points type distributor and coil...

Connect the positive side of the tach to the positive side of the coil.
The positive side of the coil is switched ON with the ignition switch.
(even works with some non-points electronic distributors)
 

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Attached are several of "Ford's suggestions. Note that all use a feed off of the ignition switch. However, as noted previously, any feed that is 12 volt powered when the ignition switch is in the "On" position (like radio, heater blower, power side of wiper motor switch, should suffice.

Bob

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