What's says 'hot' during start?

[denver98]

I need to tap a good power source that is hot with the key in the on and start positions and not hot in the off position.

Thoughts?

[histoy]

Hot wire to ballast resistor is one choice.

[denver98]

I was hoping for one inside the car but that will work too.

Thanks

[John_Kunkel]

The "hot" wire on the ballast shuts off in Start. There is no keyed wire that is battery voltage in both Start and Run.

What are you trying to do?

[histoy]

You're right John.  I overlooked that he wanted it hot in the start position, as well as the run position.  Sorry for the bum info.

[denver98]

I'm installing the edelbrock EFI system.  The ecu needs power during the start. The power provided to the coil should be hot during start.  So there has to be something I can tap. 

[RECHRGD]

Maybe put in a relay controlled by the "start" wire and feed an unswitched hot through it to the coil.   

[RECHRGD]

OK, I read again what your doing.  You could still feed the ECU via a relay instead of the coil.  Leave the coil being fed from the run circuit off the ignition switch. 

[Nacho-RT74]

Although is truth the ign key feeds just one source at the time in RUN and in Start, the ballast resistor becomes in a power splice when is connected, and all the ign system gets powered in both positions. The ECU gets power in both positions... in RUN straight from the ign switch, in Start throught the ballast when the coil is full feeded from ign key via the ballast bypass.

So even with a power decay, you'll get power on both sides of ballast no matter where you connect.

the diff is WHEN you need full 12 Volts or the low voltage source.

In RUN, the Blue side of ballast gets 12 volts and the brown side gets the decreased power

In Start, just right the opposite. Thats why you'll see the brake light on cluster ( which originall is directly sourced from blue wiring on car ) being dimmed when cranking.

The question is... does the EFI system needs full 12 volts while cranking ? or just a trigger signal, where usually just a small power source is enough to make it work ?

[denver98]

The manual says a 12v source in both on and start.  Thats all it says.

[Dino]

The manual says a 12v source in both on and start.  Thats all it says.

Find the red wire at the ashtray, that's constant 12v.  Right next to it you'll find an orange wire, that's 12v with ignition on and start.  Tap away.

Of course be sure to measure the actual wire before you do anything else, I have been known to be wrong...from time to time...

[John_Kunkel]

"Key on" is the key phrase.

What ignition system are you using? If it's an aftermarket ignition that doesn't need a ballast resistor you can eliminate the ballast and tie the wires on both sides of the ballast together to get a 12 source in both Start and Run.

[Nacho-RT74]

or remove the resistor inside the ceramic, installing a jumper wire in place to keep wiring and look untouched. Then use the wire to + lead of coil for this source.

just giving ideas

[denver98]

Thanks for all the info. They manual says that the only wires that should go to the coil are the two provided as part of the wiring harness from the ECU.  They have a port for the tack as part of the wire harness.  So, I would imagine that the ballast resistor is no longer needed.  Everything is run through the ECU now, so I want to be doubly sure its getting good power. 

[Nacho-RT74]

so pretty much the same than a MSD.

[denver98]

Yes, the kit came with an msd coil.

[1974dodgecharger]

The manual says a 12v source in both on and start.  Thats all it says.

Find the red wire at the ashtray, that's constant 12v.  Right next to it you'll find an orange wire, that's 12v with ignition on and start.  Tap away.

Of course be sure to measure the actual wire before you do anything else, I have been known to be wrong...from time to time...

Hmm off topic sorry but could this be where I could tap my amps and radio into?

[MaximRecoil]

Hmm off topic sorry but could this be where I could tap my amps and radio into?

"Amps" as in car audio amplifiers? You need to power external audio amplifiers directly from the battery. Run a new wire of a gauge appropriate for the combined power of your amplifiers (see here), with a fuse in the wire close to the battery, and use a power distribution block mounted close to your amplifiers to split the single heavy wire from the battery into multiple smaller wires to go to each amplifier. Ground the amplifiers to the car's chassis, making sure the connection is clean and tight, and that the ground wire is as heavy as the power wire.

For your radio you need a switched hot wire (only hot when key is in run position) for the main source of power, and you can get this from the sources mentioned above. You don't need a direct power wire to the battery because in-dash radios (head units) have a low power draw. You also need a constantly hot wire for the radio's memory, which can be sourced from anywhere you can find it (extremely low power draw).  

[Dino]

The manual says a 12v source in both on and start.  Thats all it says.

Find the red wire at the ashtray, that's constant 12v.  Right next to it you'll find an orange wire, that's 12v with ignition on and start.  Tap away.

Of course be sure to measure the actual wire before you do anything else, I have been known to be wrong...from time to time...

Hmm off topic sorry but could this be where I could tap my amps and radio into?

What MaximRecoil said.   

My aftermarket radio is hooked up to those red and orange wires to have power on with ignition and constant for the memory.

[Nacho-RT74]

note... you'll never cut out the power if splicing from there