Team Camaro Tech banner

1 - 13 of 13 Posts

·
Registered
Joined
·
81 Posts
Discussion Starter #1
I'm finishing up my EZ EFI install and I need a switched 12 volt source for all the new electrical devices that are part of the new setup. The ECU for the EFI, the Mallory Hyfire 6 ignition box, the fuel pump relay and the electric fan relay all need switch 12 volts (in addition to hot 12v from the battery - I've got that covered).

For a 69, where's the best source for switched 12 under the hood? The old choke wire for the carb (gone now!) and the resistance wire to the coil (removed in favor of 14 gauge black wire since the coil needs a full 12V now and has a built in ballast resistor) seem like the best candidates. Are these "on" at ignition AND crank / run? Can I run all these to one source or do I need more sources for switched 12 than just the one?

Thanks
Bob
 

·
Premium Member
Joined
·
2,118 Posts
A switched 12 volt from the fuse box to activate any number of relays for mentioned components. Each relay with a fused battery 12 volts suppply and 12 ga cable, at least from battery supply to relays, and from relays to components.JMO
 

·
Registered
Joined
·
81 Posts
Discussion Starter #3
Which slot on the fuse box is available and acceptable to use?

Thanks
Bob
 

·
Registered
Joined
·
8,349 Posts
Hey Bob. You can just make a fused pigtail with a female spade terminal on one end and plug it onto the spade marked "IGN" on your fuse panel and run it through the firewall. It's got plenty of juice to do what you want since you're just firing a couple of relays and turning on a couple of boxes. You probably want to install quenching diodes on your relays if you don't have them already.

I'm running an HEI and my EFI ECM without an issue from my IGN spade.
 
  • Like
Reactions: Calpantera

·
Registered
Joined
·
81 Posts
Discussion Starter #6
Steiner;

How much can I connect to that "IGN" 12v switched source? Can I connect the fan and fuel pump relays, the EFI ECM, the ignition box AND the coil to it (it's a Mallory Promaster e Coil- full 12v reqd) ? Or should I split things up? I have a 5 amp fuse on a 14 GA wire connected to the "IGN" on the fuse box...is that OK?

Thanks
Bob
 

·
Registered
Joined
·
8,349 Posts
I would put in a 15A fuse as that's what 14AWG wire is rated for. You'll most likely be over 5A on the circuit as well.

Your two relay coils are going to draw a very small amount of current, well under an amp.

The ECM will probably not draw much, say two amps just to have something. It has another 12V connection from the battery, correct?

The box will not draw much either, maybe a couple of amps max as it is just the turn on power from the ignition.

Concerning the coil, isn't it fed directly from the Hyfire box? If so, then that supply is coming from the battery not the IGN circuit.

The starter solenoid shouldn't draw very much if it is in good condition.

I think you'll be safe with everything on the IGN circuit. If the coil is fed from the Hyfire box and it's not that Digital EZ thing they have that uses your old coil to feed the box then it feeds the E Coil then you're looking at less than ten amps on the circuit.

Even if it is the type that uses your old coil as the "trigger" for the box it shouldn't have much draw as the 12V battery supply from the box should be feeding the E Coil and your distributor.
 

·
Registered
Joined
·
8,349 Posts
You bet.
 

·
Registered
Joined
·
81 Posts
Discussion Starter #10
The Hyfire box has a feed to + (orange) and - (black) on the coil..... that said, it sounds like the Hyfire box is providing the 12v to the coil.... would that mean that supplying 12v from another switched source to the coil is redundant (perhaps even a problem)?

Bob
 

·
Registered
Joined
·
8,349 Posts
Correct. The feed from the Hyfire box should be the only thing on the coil other than the coil wire to the distributor. The box uses the IGN source as its turn on signal, but the main power is supplied by the large cables coming from it that are connected directly to the battery. So, the ignition itself will not have much draw from the IGN circuit. The instructions should say it's the only thing that should be on the coil. Remember it's a high output box so it's stepping up the voltage being supplied to the coil.

They do make a Hyfire system that uses your old coil which connects to the box and then a new coil that actually feeds the distributor. That's not they one you're running, right? Just a regular Hyfire VI?
 

·
Registered
Joined
·
5,277 Posts
I've always had dreams of snagging a modern under-hood fuse / relay panel from a junk yard vehicle and using it for powering accessories and ignition related devices. I believe the pins in most of those are standard packard terminals that can be removed and replaced with a new wire on a new terminal to do whatever you want.
 
1 - 13 of 13 Posts
Top