Do I need a relay for the starter signal wire with late model starter?

[RyanG85]

I put a 90's mustang 302 starter on my 65 and removed the solenoid from the fire wall. I remember reading a while back that some say a relay should be used. I hooked it up without and everything seems to work fine but I've only started it a few times. Should I be using one and why?

Thanks

 

[RyanG85]

Also the brown wire from the I terminal on the solenoid, Is that for the charge indicator light? What do I do with that? I'm running a 3G alt and I'll be adding an aftermarket cluster.

 

[Midlife]

Brown wire on starter solenoid is the coil run line, which gives a full 12 V to the coil while you're cranking the starter.

 

[RyanG85]

Ok, Just looking at my under hood harness and I see the red/green and brown go to the same terminal. That makes sense. So what do I do with that wire if the solenoid has been eliminated? With the Pertronix Ignitor III ignition, is it needed? I've started the car a few times without and it was fine. Also, should the red/blue run off a relay?

 

[Midlife]

Red/blue is normally the crank signal line, controlled by the Neutral Safety Switch.

 

[RyanG85]

Red/Blue my mistake. I've been doing some online reading and it seems I need to install a relay to trigger the starter solenoid. So the red blue will trigger the relay and I'm assuming that I should put the brown wire to the solenoid side of the relay to power up while cranking. Correct?

 

[Midlife]

Not exactly. The brown wire is tied in at the firewall to the pink resistor wire. When the red/blue wire starts the starter to crank, the voltage from the battery is drawn down a bit. Together with the pink resistor wire, there may not be enough voltage to the coil to actually cause the engine to catch. When the starter relay is energized with the red/blue wire, it also puts full battery voltage on the brown wire; that voltage travels to the firewall and then back to the coil. When the starter relay is de-energized, the pink resistor wire takes over as the source of voltage to the coil.

If you are using an aftermarket ignition system that bypasses the resistor wire, you don't need the brown wire any more (unless the ignition system needs it for some reason). If you're using the stock system, you definitely need to have the starter solenoid energize it with full battery voltage.

 

[RyanG85]

I got it now! I'm a little slow when it comes to electrical...... Brown wire will be eliminated and the red/green will go to the coil but eliminate the pink resistor wire under the dash and replace with a B+ run wire. The Red/Blue will trigger a relay for the starter motor. I'm good at making things more difficult than they need to be.