A good source for constant power?

[danf_fl]

I am installing electronic actuators for head light doors on '68 Charger.
It has three wires for connecting.
Return
Dimmer switch
and third is for a "constant" power.

I can do return (ground), and can tap the wire to the dimmer switch (provides power to open doors), but what is a good place to get "constant" power (to close doors when lights are off)?

 

[Gold Rush]

I am installing electronic actuators for head light doors on '68 Charger.
It has three wires for connecting.
Return
Dimmer switch
and third is for a "constant" power.

I can do return (ground), and can tap the wire to the dimmer switch (provides power to open doors), but what is a good place to get "constant" power (to close doors when lights are off)?

Probably the easiest would be the large terminal on the start relay mounted on the firewall above the steering column. You could tap into the ignition switch constant feed line at the large connector attached to the steering column under the dash but I hesitate taping into wires if there is an easy alternative. Its is aways best to stay away from slaving directly to the battery terminal. Too much corrosion potential there.

 

[Nacho-RT74]

Nothing must be sourced from the line between batt and ammeter. Anything needing constant batt source must be sourced between ammeter and alt on cars with ammeters.

ALTHOUGHT, stock electric systems for later models are sourced from the run circuit ( which is in any case on the correct ammeter side ) without need for batt power.

Do those systems REALLY sucks more power than the stock motors to REALLY need to be sourced from battery line ? I don't think so!

You can take it from regulator blue wire to be sure will be energized just when car is in RUN.

Stock systems get in fact the relay inside the cab, to take the trigger to open doors from The line between the floor dimmer switch light green wire and headlight switch. Then the source from same blue line at ign switch ( 3rd gens got RUN circuits provisions ready to be used on harness to feed some stuff and save from splice into wires, can't tell if earliers )

Getting the source from RUN circuit will allow you to service headlights with doors open and headlights off. Being constant will close the doors at soon you turn off the lights even with ignition switch off.

 

[danf_fl]

If I am reading my wiring diagram correctly, I should be able to use the Rear Window Defogger supply at the fuse box (after the fuse). That is an "accessory" that runs only when key is on and my car does not have that option.

Opinions?

 

[Nacho-RT74]

That's an option too. Stock systems use a breaker in line with the main source coming from run circuit in case of a headlight motor failure, able to open the circuit if points inside the motor gets stuck. Using the heater feed should be protected by the fuse. The diff is the breaker will reset by itself after the failure is fixed or motor disconected, the fuse will blow and will need to be replaced, but both protects the system in one or another way.

 

[danf_fl]

Thanks!
Going with the fuse should indicate a problem if it blows, and will not take out the rest of the circuit (I still could drive in daylight).