[Gramps]

The instructions for my Autometer Tach says "red wire to ignition". Can I just slip this red wire into the radio fuse? Is the main thing that this red wire is hooked up to a fuse that is on when the car is on?

[BlazinPlubes]

The red wire is going to be a fused 12v KO (key on) source of voltage. It explain that in the instructions. Take your testlight and probe KOEO voltage source. Make sure its not a random wire, or you could have other problems with fuses blowing due to the extra current draw or also driveabilty problems if connected into the wrong circuit.

Best of luck

[Holder350]

yep any wire that is hot while the key is in the run position.

RED - power
WHITE - Ilum
BLACK - ground
GREEN - coil

[Gramps]

Thanks...that clears it up for me.

[79C10]

Actually , the radio wire is the last place to hook it up. You'll likely end up with "ignition hum" in your speakers. I run mine to the accy. fuse in the fuse panel.

[Gramps]

Originally Posted by 79C10

Actually , the radio wire is the last place to hook it up. You'll likely end up with "ignition hum" in your speakers. I run mine to the accy. fuse in the fuse panel.

Good point...I will find a live fuse spot...accy sounds like a good spot...I can't remember if I have an accessory fuse spot.....weather is was too nice today to work on it...I hate to pass up a sunny day for cruising

[Holder350]

Acc and radio tie in together.

think about it.....unless theres a fuse blown ALL power wires are tied together somewhere.

most modern tachs will not cause interferance with other electronics.

"Igniton hum" is mostly due to a improperly shielded antenna cable (or to close to spark plug wires) or speaker wires run to close to a power wire.

The electromagnetic field around the power and spark plug wires cause the interfence.

[79C10]

Originally Posted by Holder350

Acc and radio tie in together.

think about it.....unless theres a fuse blown ALL power wires are tied together somewhere.

most modern tachs will not cause interferance with other electronics.

"Igniton hum" is mostly due to a improperly shielded antenna cable (or to close to spark plug wires) or speaker wires run to close to a power wire.

The electromagnetic field around the power and spark plug wires cause the interfence.

I'll not go back and forth over stereo installation . I have installed dozens upon dozens of stereos/amps/ EQ's/ crossovers , etc.
I just got done dropping in an amp and door speakers today in fact. Antenna wires don't come anywhere NEAR your spark plug wires and speaker wires don't pick up interference from outside sources. To eliminate I.H. , you install a buffer on the positive POWER wire. or hook it up properly to begin with. You definitely don't hook up ignition accessories to your radio power wire though . Unless you like the whine that comes along with it.
What's next? Forgoing the fuse next to the power block at the battery ?

[Holder350]

Most all modern stereos have a buffer either in the stereo or in the line about 3 inches down.

But all this aside the power wire for the tach will not cause interferance with the radio if connected with it.

Tach signal is - so I seriously doubt you wold have a problem unless you had a bad tach ground.

[Gramps]

Thanks for all the input...hopefully tomorrow after work I will start this project. Looks like the hardest part might be getting the wire to the distributer in the '28.

[Holder350]

Dont know what year your working no but most all HEIs have a tach lead on the cap.

you can remove the cap hook it up then reinstall.

Might make it easier

[Gramps]

I did it and I didn't break anything!!! I should have said the green wire to the tach and not the red wire.
The light on the tach is on all the time...I guess this is no big deal except it will burn out the light quicker. I think it is on because I have the tach hooked up to the acc fuse. I will play with it one day and see what works best.
Thanks for all your feedback. It is much appreciated to guys like me who are a little unsure on how to do things.

[hotrod66_57]

The light being on all the time should just be because your power source for the (is it white wire) is something that is on when ever the key is on. If you really want to go all the way track down the wires for your instrument cluster lights and feed that white wire power from there. That way you'll have your backlight whenever you have your dash lights / headlights on. Or you could put in a switch for the backlight, or, like you have it now just live with the light being on all the time lol

[79C10]

Gramps,
Run the white wire to your headlight fuse. This way , the light only comes on when you turn on your lights , plus it'll dim down with your dash lights when you rotate the headlight switch. It'll work like a charm.
Best of luck,
Mike

[Gramps]

I will try that 79C10.
Thanks