Brain fade I suppose, and not near the car or FSM.
Want to use a 12V switched terminal for an added tach, and since I'm running the coil & neg leads to the engine, I'm thinking running the tach power to the SR would be clever & easier than pulling the ign switch. Also easier to deal with should I later remove the tach.
'68 Road Runner 4-speed car if that matters.
Thanks.

I'd look for another source, as none of the starter relay terminals are "run only" power.

You could just hook it to a fuse box terminal. No need to pull the ignition switch.Use one of these.

Thanks, Buildanother.
Stumpy, I've done the fuse box tap before by modifying a spade connector, but was never all that impressed with it.
Never seen the clip you posted, that's pretty clever.

Available at most parts stores.

A "run" terminal in the fuse box? I think all you'll find there is ACC and BAT. Using ACC in the fuse panel will power the tach in accessory position. Best to use the blue wire on the voltage regulator for RUN power.

There are key on powered fuses.

& make sure how you feed it (the 12V) goes thru a fuse or add an inline fuse (5amp?).

Where? What circuit? All key-on circuits in the fuse box are accessories, not RUN.

If I'm remembering correctly the radio, heater and several other circuits that are in the fuse box are run only with the key in the on position, correct
OP you can remove the Phillip head screw that holds the fuse box onto the dash frame and drop it down so you can pull the plastic dust cover off the back side and use one of the unused spade tip to feed your tach with the key on

Ever turn the key to ACC just to listen to the radio with the engine off? Yes, ACC circuits are powered with the key in RUN but a tach should be powered by a dedicated RUN circuit otherwise it will be powered with the key in ACC.

John, I like the Run side of the voltage reg; easy to piggy-back, and no doubt what's what. Plus I have some OEM-style connectors. I figure a 5A fuse like Robert says is wise.
Back in the day running the power from the fusebox, maybe the thing that saved me was (a) I almost never use the Acc key position or (b) I picked up the power from the On side of the fuse?
Thanks, guys.

For the record, the repro in-dash tach is no more accurate than they were back in the day, it's more entertainment than factual.

what harm is there in having the tach powered in acc?

It freaks out your OCD

I prefer to use the VR run source to trigger relays that provide power to whatever source needs it in run. Don't like to load down the VR run line as it will affect the VR's operation and MoPar's charging system isn't all that sophisticated.