While preparing to install a PerTronix Ignitor III in the Motorcraft distributor of my stock 302 2v Maverick, I relearned several things ignition-related. First, the notoriously inaccessible and stupidly engineered distributor-hold-down bolt truly earns its reputation on air-conditioned vehicles. The compressor is unhelpfully placed. I went and bought the special wrench, disconnected the fuel line from the carburetor (to move the hard-line) and it was still slow and tedious. My second collection of renewed knowledge was learned on the electronics side. PerTronix instructions tell you to bypass the resistor when you are converting from points. I’d forgotten even cars had resistors in the ignition system, but it’s really important to know when you’re upgrading to a solid-state ignition. As it turns out, PerTronix Ignitors run on standard automotive voltage (14 volts), but the original point and condenser ignition normally operate at 9 volts. The ballast resistor on cars equipped with points drop the voltage. (Except when the starter is engaged, when the coil receives an extra, momentary boost up to the full 12-14.5 volts, but that’s another story). Many cars have an obvious ceramic resistor block (about the size of a piece of chalk, if chalk had wires sticking out of it), often located with the coil, near the starter solenoid or on the firewall. Our cars (or at least my ’73) don’t have this. Instead, it has a run of resistor wire in the circuit between the ignition switch and the positive terminal coil. To distinguish it from other wires, it’s pink. It’s a rather elegant solution from the engineering and manufacturing perspective. Unfortunately for my purposes, the pink wire runs from somewhere in the harness under the dash to the ignition switch. The “correct fix” would be to remove the steering wheel, drop the steering column, replace the pink resistor ballast wire with regular 18-gauge copper and reassemble. I’m not going to do that. My workaround will be to run a wire from any switched circuit (haven't decided which one). That means my ignition switch will send power to the coil in any position other than OFF. While I loose the functionality of the ACC setting on the ignition switch, I can live with that. I researched a number of other kludges and found none of them satisfactory. My first instinct was to find transformer to bump up the voltage from 9 volts to 14 volts. Such things exist, but they are expensive and designed to operate inside the case of a computer, not under the hood of a car. The next idea was to wire in a relay, like hooking up fog lights. Turn the key to on, 9 volts is sent the relay, which in turn sends 14 volts to the coil. Unfortunately, commonly available relays present problems. First off, the ones made for automotive purposes generally specify a minimum of 12 volts to trigger (control voltage). And then there’s the voltage surge problem. Relays act like little itty-bitty coils. When the relay gets turned off, its magnetic field collapses (like a coil) and there a spike in voltage. Those spikes can damage solid state electronics – a lesson installers of car alarms and door locks learned the hard way. The fix for relays used upstream of solid-state circuitry is to use a relay with an integrated diode. But then, you’re still adding even more complexity, which is seldom a good thing. Meanwhile, I’m just going to wire up the PerTronix Ignitor to a switched circuit. Thoughts? All recommendations, sanity checks or corrections of my misunderstandings are welcome.
You are overthinking, use the ign "jumper feed" wire on solenoid to trigger a relay that supplies 12v directly from battery, problem solved... All the 12v relays I've seen will trigger on roughly 8v(I've tested several with a variable 0-25v power supply)... Without coil feeding from the resistance wire(that Ford used from the early '60s), voltage will be around 12v anyway... No load on resistor, no voltage drop(or at least relay coil will only drop voltage maybe .2v)... It's how electrical circuits work... Both my Comet and Cobra Jet have a relay triggered from the resistor wire... For surge suppression it's easy enough to add a 1N4007 rectifier across relay coil, I've never bothered...
I have mine just like Tom's - here is a picture. I used the Pertronix relay. The purple wire spliced into the ignition wire at the solenoid is the relay trigger wire. Works great!
Eric, you can loosen nut on solenoid just enough to slip a spade terminal under it and retighten... Of course if the plug on terminal slips off you would loose ignition... That's how I have my C Jet, but at present the relay only operates choke... I have one of the original Pertronix units(now known as Ignitor-I?) in dist also powered from resistor wire... BUT instead of driving coil, it triggers a Crane Hi-6 powered directly from battery... Been using this hookup for over 20 years, relay for choke has only been in place a couple months...
Funny enough story. My harness had damaged insulation at the spot I put the trigger wire. I would have needed to repair that spot anyway. This spring I'm going to clean up a lot of that wiring into the black loom tubing so it won't look so "busy" around that VR and solenoid. Good to know you can loosen up that nut and get a spade terminal on there .................
I was going to remove nut but as it loosened, the terminal would slide deeper into solenoid, decided was best not to chance losing it inside... Sooo I clipped out a section of a ringed terminal and slid it under nut... For benefit of OP, I have a Painless seven circuit fuse panel on Comet that gets power from relay(I believe four are switched by relay & three direct)... I use switched for electric fan, Ign, choke and direct for headlight relays..
Thanks I was still installing fuse panel when pict was taken... The solenoid & battery cable/starter harness is from a '96 Ranger, bullet connector on relay trigger lead is plugged into original connector to solenoid(the Ranger solenoid doesn't have the ignition feed)... Used OEM plastic covers for battery terminals... Internal regulator alternator from a '88 T-Bird... Yeah it's a crappy 2G, but has been fine...
