Where is the best source for keyed 12v power ?

[RON REAGLE]

I need to connect a couple "key on" 12 volt power wires on my Cuda. There already wires connected to the male spades at the bottom of the fuse block and I don't want to add more there . Is there a way to mount an additional block under the hood that would only have power with the key on ? Maybe off the starter relay ?

 

[TT5.9mag]

Add a fused circuit off of the original fuse block, that triggers a relay. Depending on power requirements you can pull the 12v from any source, battery, starter relay, etc.

 

[dano]

I added an extra Painless fuse block to my glove box for all my switch and direct power aftermarket items. Runs directly off the battery with a circuit breaker and then fuses for each circuit. This takes the load of the factory wiring.

 

[TT5.9mag]

This takes the load of the factory wiring.

Any load you pull from the battery is seen by the ammeter and associated factory wiring.

 

[crackedback]

Add a fused circuit off of the original fuse block, that triggers a relay. Depending on power requirements you can pull the 12v from any source, battery, starter relay, etc.

This ^^^^^

If you have the OEM charge path in place or from the alternator. Have a switched trigger wire tell the relay to contact. Keep as much load off the factory harness as you can.

If you have a direct charge wire then pull for accessories from wherever you like.

 

[Professor Fate]

Depending on ŵhat you're looking to run and what kind of loads you're going to put on it, under the hood you can tap into the (normally) blue ign.+ wire that is normally used for things like electric choke and the ac switch. You can use it as a relay trigger if your projected load is going to surpass what that circuit can safely handle.

 

[crackedback]

Depending on ŵhat you're looking to run and what kind of loads you're going to put on it, under the hood you can tap into the (normally) blue ign.+ wire that is normally used for things like electric choke and the ac switch. You can use it as a relay trigger if your projected load is going to surpass what that circuit can safely handle.

Seen tons of cars with the blue wire cooked in the engine and dash harness from loading it up with those things (choke, ign box, alt excite/sense). I usually suggest using it for a trigger and everything is fed off a bosch relay.

Splice the brown/blue wire together like you would for an MSD install and you have start/run covered.

 

[Dana67Dart]

If it was me... I would get 12V power at the Alternator post.
run that to a relay properly sized for the load you are trying to power.
the trigger for the starter relay could come off the IGN 1 as long as its not powering anything that needs to be powered while starting

 

[crackedback]

If it was me... I would get 12V power at the Alternator post.
run that to a relay (ford type starter relay would have huge current carrying capacity) you could use a smaller relay depending on what you are trying to power.
the trigger for the starter relay could come off the IGN 1 as long as its not powering anything that needs to be powered while starting

You don't need a ford relay to run those items. A std 4 pin 40 amp bosch relay that triggers with 1/4-1/3 amp instead of that big winding in a ford/CD relay would do just fine. That ford relay probably draws more current than the stuff you want to feed!

 

[Dana67Dart]

You don't need a ford relay to run those items. A std 4 pin 40 amp bosch relay that triggers with 1/4-1/3 amp instead of that big winding in a ford/CD relay would do just fine. That ford relay probably draws more current than the stuff you want to feed!

agreed I reworded my post

 

[Professor Fate]

Seen tons of cars with the blue wire cooked in the engine and dash harness from loading it up with those things (choke, ign box, alt excite/sense). I usually suggest using it for a trigger and everything is fed off a bosch relay.

Splice the brown/blue wire together like you would for an MSD install and you have start/run covered.

Yeah, you definitely don't want to overload it. The most I've seen from the factory is elect. choke assist, a/c switch and electric bowl vent for some of the later Thermoquads (in addition to the ign. & alt., of course). Any more than that I'd run a relay; although if none of that is present you may get away with a low-draw load. Hard to say without knowing exactly what the OP is trying to hook up.

 

[Bewy]

Depending on how this new load is wired/connected, it may NOT be seen by the ammeter. You can buy a small, compact 150 amp relay that does everything the big, obnoxious Ferd relay does.

 

[AbodyBB]

hope I can help with some wisdom here that I’ve gained after burning a few harnesses.
1.) wire itself on these old harnesses are capable of carrying 10-13 amps. That’s more than enough for older accessories. When we add fans etc those are much higher draw and require larger conductors.
2.) anytime you cut/splice/connect in a wire, you introduce a higher resistance connection that heats up under load. Make your connections at factory places since those are specifically for heat dissipation.

So if you are looking for a switched supply go to the back of the fuse box and find the black wire. I am not certain on the color but there’s only three circuits that split at the fuse box. Dash lights constant 12 and accessory or switched. So you’re looking for the accessory circuit. Use this
https://www.oreillyauto.com/detail/...MIpZqEp7edlAMV0SGtBh3lWQxzEAQYByACEgLKRvD_BwE

to piggy back on any fuse.

 

[RON REAGLE]

I bought a relay kit for my electric fans to turn them on at 180 degrees. There's a small red wire that needed 12v to trigger the fans which are connected to the battery direct for main power. I also have an idle solenoid on my six pack set up that needs a key on 12v power source. I made a jumper and used the acc male at the bottom of my fuse box. I connected it to a 4 terminal add-on fuse block with 20 amp fuses (do I need to lower their amperage ?) Everything now has power am I risking an overload ?

 

[AbodyBB]

Yes lower fuses to 15A as long as the wires are not in a bundle. Drop to ten if bundled. If you can operate on a 10 amp then I’d go to the ten. Fuses are used to protect the wire not the accessory that it’s operating.
Electric fans should have their own supply wire so that shouldn’t overload. What is supplying the output of the solenoid? Did you pull a large wire from the battery?
Any wire pulled from the battery or the back of the alternator should be fused.

 

[Dana67Dart]

BTW, the acc cir will be live in RUN and in ACC BUT not in start.

 

[AbodyBB]

Thanks for that. It’s been a while since I’ve driven my stuff. I had forgotten the acc circuit shuts off for the start