12 volt constant

[cuedog10]

I need a 12 volt constant going thru the key switch. Does anyone know which wire I need to use? 1972 Mach 1.   Thanks

 

[Don C]

Do you mean 12 volts all the time, whether the key is on or off, or just when the key is on?

 

[cuedog10]

Just with the key on.

 

[Aus73Mach1]

I need a 12 volt constant going thru the key switch. Does anyone know which wire I need to use? 1972 Mach 1.   Thanks

There is a post on the fuse box marked accessory post. Depends what you want power for but it is on a 20 amp fuse and a long bolt to fit several cables.

 

[MustangNJ]

thats the post I used. because I was adding a number of accessories, I added a 3 circuit Aux fuse panel, using the keyed-on fuse ( + to battery). adding accessories to these old style panels is something I don't like, so I add the extra fuse box

 

[jpaz]

Not all cars have the accessory post.

 

[Hemikiller]

Buy an accessory post for the car, if it's not present

https://secure.cougarpartscatalog.com/c8oz-14a033-c.html?attribs=81

You can use one of the fuse tap products to get your 12V from the accessory fuse clip, and use an inline fuse.

https://www.amazon.com/Wirthco-0303-1233-Battery-Doctor-Roundtapper/dp/B000CQDRSE/ref=pd_sbs_60_t_0/130-1465162-7814324?_encoding=UTF8&pd_rd_i=B000CQDRSE&pd_rd_r=f0453977-d130-4180-9ebc-38e9ecf303d4&pd_rd_w=iHICj&pd_rd_wg=eNysP&pf_rd_p=5cfcfe89-300f-47d2-b1ad-a4e27203a02a&pf_rd_r=AP2A2V89XQJSWK126NCE&psc=1&refRID=AP2A2V89XQJSWK126NCE

What are you looking to power with the keyed 12V source?

 

[Don C]

Midlife has the extension for sale, also, for $15. That extension provides 12 volts when the switch is in run or accessory and is fused at 20 amps.

http://midlifeharness.com/products.html

The existing wire that is NOT fused is black with light green hash marks and provides 12 volts in run and accessory.

The wire that is NOT fused that provides power to the engine in the run only position is red with a light green stripe.

The ignition switch was not designed for heavy power loads, and the main power feed (yellow wire) to it is not large enough for heavy loads. If whatever you are connecting to it draws more than 15 or 20 amps you will have to power it directly from the battery through a relay. If you connect to either of the above wires you MUST add a fuse to it immediately after the connection, even if you're just running it to activate a relay.

You can download the wiring diagram by going to the "Mustang Data" pull down menu tab in the upper right of this page.

You can learn how to read wiring diagrams in the attachment in this thread

https://www.7173mustangs.com/thread-how-to-read-wiring-diagrams?pid=336055#pid336055

 

[cuedog10]

Buy an accessory post for the car, if it's not present

https://secure.cougarpartscatalog.com/c8oz-14a033-c.html?attribs=81

You can use one of the fuse tap products to get your 12V from the accessory fuse clip, and use an inline fuse.

https://www.amazon.com/Wirthco-0303-1233-Battery-Doctor-Roundtapper/dp/B000CQDRSE/ref=pd_sbs_60_t_0/130-1465162-7814324?_encoding=UTF8&pd_rd_i=B000CQDRSE&pd_rd_r=f0453977-d130-4180-9ebc-38e9ecf303d4&pd_rd_w=iHICj&pd_rd_wg=eNysP&pf_rd_p=5cfcfe89-300f-47d2-b1ad-a4e27203a02a&pf_rd_r=AP2A2V89XQJSWK126NCE&psc=1&refRID=AP2A2V89XQJSWK126NCE

What are you looking to power with the keyed 12V source?

 

[cuedog10]

I have a dist. with an electronic ignition. I need 12 volts during cranking and after starting. I want to be able to start the engine as well as turn the engine with the key.

 

[Don C]

Get this relay from Pertronix, activated by the existing coil wire, and provide 12 volts directly from the battery.

https://pertronix.com/pertronix-2001-ignition-power-relay-kit.html#.XanbRTNlDkA

 

[MustangNJ]

I would never run an accessory load directly off the fuse block. I use the keyed-fuse to connect to a relay. almost no amp draw.

 

[Hemikiller]

I have a dist. with an electronic ignition. I need 12 volts during cranking and after starting. I want to be able to start the engine as well as turn the engine with the key.

Your electronic ignition needs to be powered not only in "run", but in "start" as well. 12V power in "run" is not the same as "start", the only systems generally powered in "start" are the starter solenoid, the bulb check circuit and the coil (through the I terminal on the starter solenoid). 

If this is the same unit you posted about earlier, have you gotten any instructions for it from the seller?

*** edit***

Here's what I'm guessing you've bought.

https://www.jegs.com/i/Speedmaster/746/PCE376.1085/10002/-1

and the instructions I managed to find are attached. 

IMO, this unit a complete POS. I bought one out of curiosity and it was absolute junk, so it went back. But if you insist, then you need to follow the attached PDF and bypass the resistor wire in the dash harness for it to work properly. You can then power it directly off the coil (+) which will then have 12V.

PCdistributor.pdf

 

[Don C]

The old adage "you get what you pay for" certainly applies here. Kind of a strange looking vacuum advance, obviously not adjustable. Most everything that begins with "pro" is anything but. I think that Proto tools is about the only exception I can think of. I have some that are over 50 years old.

A stock distributor with a Pertronix II would be much (by several times) better. Adjustable vacuum advance, adjustable centrifugal advance curve by changing springs, easily obtainable repair parts or rebuilt. And, if the electronic module ever fails pull the points and condenser out of the glove box.

A little digging at a Pik-n-Pull would get him a DuraSpark for less.

 

[JJU9507]

pro comp electronics is total chinese counterfeit garbage p.o.s., only noobs should attempt to run their crap!!

 

[Grandmas73]

I need a 12 volt constant going thru the key switch. Does anyone know which wire I need to use? 1972 Mach 1. Thanks

Not sure about your setup but on my 73 302 I was able to pick up the 12v source here at the carb. It’s been a while but I followed the wiring diagram and felt this source was ample to supply my pertonix, take a look (it did involve soldering)
The rubber cap comes of an allows you to tack onto the 12 tap. On with the key, no dropout when cranking. Still needs a little clean up but definitely more hidden then a relay fed source
Hope it helps.