KJL

I am looking for a location to wire an ignition control unit to. This would have to be energized upon ignition and stay energized after start up. There are several locations for a switched 12 volt supply but they de-energize at ignition. I wired a Pertronix unit to one of these and because it turns off at ignition, there car would not start. :conehead If I installed a MSD 6AL, would I use the coil hot lead ? My car is a "72" L48

Thanks

GaryS

I would say that the easiest way to find either an unswitched or switched source is to use your multimeter set on the 20 volt range and look for power. All you will need to do is to find a likely source, with no power to it with the ignition off then turn the ignition to Run to ensure that it is powered. We did this on my buddies 73 when we were trying to find a switched power source for his choke thermostat. It took about five minutes before we found a suitable source. If you don't own a mulitmeter, Sears and Home Depot sell some inexpensive ones for a reasonable price. My first thought is the windshield washer pump circuits. Next would be the power window wire connector (if you have them) on the driver's side, just above the steering column. The sources are fairly endless, just using the engine compartment wiring diagram.

Gary

7t2vette

I also have a 72 that I installed a MSD 6AL box into. You can wire the small red wire from the 6AL to the original coil +wire. It is a source of keyed 12v power.


Regards

Bruce

KJL

Trying to find a 12 volt power supply that is switched but does not temp cut out at ignition is not as easy as one may think. I have been all over the engine compartment with a volt meter, and every switched 12 volt source I found with the exception of the coil + wire, cuts out at ingnition.

rainman69

Install a relay off the coil+ wire...that way, there's not excessive amperage draw on the wire, and you can then hook anything to it. :smash:

e3pres

The windshield wiper 'hot' wire is energized as you need. I'm using it for my electric choke, however, you may be pulling too much juice for it. It is fairly small.

KJL

I bet ya 5 bucks if you put a volt meter on it you will find it temporarily cuts out as you start the engine.... :D

john's '81 mouse

Quote: Install a relay off the coil+ wire...that way, there's not excessive amperage draw on the wire, and you can then hook anything to it. "

I agree with above, it's by far the best solution, that way you can wire a good heavy wire from power to the relay, and not worry about whether you're getting enough voltage.

KJL

Ok, so I would use coil power to trip a relay which would control a source of un-switched power?

James

I may not understand exactly what you need but could you not get a constant 12 volts all the time from the starter where the battery connects to it?

KJL

Some of the distributor pointless conversion products out there funtion best when hooked up to a clean 12 volt power supply. The trick is to find one that is switched and does not temporarily "cut out" upon ingnition. Most switched sources of power are designed to cut-out so more power is available for the starting process ie coil, starter etc. Ever notice the switched components will stop when you start your car..radia, wipers, AC..... :crazy:

ANGIE82

THE BEST PLACE TO TAP IN IS THE STARTER, BECAUSE IT HAS ALL THE POWER YOU NEED.

paso

I agree with this it is the best location of "LIVE " power not Keyed power.

74ZZ430

I recently installed the Pertronics II on my 74, I was able to find a 12 volt source that stayed hot while cranking the motor. It was located right in the midddle of the fuse box, its kinda strange but there was what looked to be a factory installed harness that had large gauge wires coming out of it that plugged onto the male terminal in the middle of the fuse box, and on the back on this harness was another male plug that I connected to.

rhoeven

This is the correct way to do it, but may I add one more suggestion:
Get a 12 V relay with a low holding voltage. The problem will be that under marginal battery conditions , the battery voltage during cranking will drop as low as 8 Volt. If the min. holding voltage of the relay is too high, the relay will de-energize and the car won't start.

Roger

KJL

Thanks for the tip, I have the same wire going into the center of my fuse box. I have not checked it yet. I just wired a new radio to the male tab just above it. It is a non switched continuous supply.