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Discussion Starter #1
Working with a 1967 Mustang, 289 C-code.

Hopefully quick question - I'm in the process of swapping out the old Autolite 2100/cast iron intake for an Edelbrock Performer 600 CFM carburetor and Performer RPM intake.

The carburetor has an e-choke on it, and in reading around a bit online it seems that the safest way to go about doing so is to use a relay to trigger the +12VDC to the choke, in order to avoid additional load on other circuits in the car. Folks have suggested hooking the trigger end of the relay to the STA terminal on the alternator - anyone have any experience with this? Any specific relays, or just any basic radio shack relay will do? I want something that will only trigger when the engine is on and running, not just at key on to avoid opening the choke if i'm listening to the radio or something while the car is off.

I've seen people wiring it into the ACC on the fuse box, onto the alternator directly, and into other +12 switched (ie Key on) sources, etc. The relay/fuse approach seems to make sense from an isolation/saftey perspective, even if it is more work/wiring to lay.

I'm going to try and wire it all up in the next few days, and will let folks know what I find
 

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I decided to make a fuse panel for my auxiliary circuits.
Here is a write up and parts used:
Aux 12V Power
Probably more than you were asking about but it gives you an idea of how to do it...
Good Luck and BE Safe
Ron
 

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Discussion Starter #3
More than I was asking for? Yes.

Valuable? Extremely!

Got your site bookmarked for future reference, thanks for the advice!
 

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I just did the very same thing regarding the electric choke. I ended up energizing the coil on the relay with a circuit that only has power when the key is in the ON position. It was a little extra work, but I also was able to put in an aftermarket stereo and have an easy switched voltage source. And there is still another contact on the relay that could be used for a switched 12 V source.

As far as the relay goes make sure it is a 12V coil and then make sure the contacts can handle the current draw of the electric choke. I believe they typically draw less than 1 amp, but at initial activation they will draw much more until they are heated up.
 

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Discussion Starter #5
Found where someone put ameter on the choke, peak draw was around 6 amps, before dropping below 1. Figured on using a 10 amp fuse and a 30 - 40 amp capable relay, so I think I should be good! Thanks for the input!
 

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Excuse the rough schematic.
This wiring will work for what you are doing:

Good Luck and BE Safe
Ron
 

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Restomod,

That circuit will not work as the starter relay only gets 12V with the key in the start position. The choke would only be engaged during the actual cranking.
 

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This is similar to the circuit I am using for my electric fan.

The left side small terminal (S) on the Starter Relay is hot when the the key is turned crank the starter. The right hand small terminal (I) gets its voltage from the key in the on position from the number 16A wire (pink resistor wire) and it also supply's voltage to the coil for spark. If you check voltage on the terminal it will be less than 12volts because of the resistor wire with the key in the on position.

Here is the print http://hammar.dyndns.org/~djhamma/wiring/1966/66ignit.jpg

Good Luck and BE Safe
Ron
 

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Discussion Starter #9
Just got home, Fry's had the relay/harness I needed, picked up a bunch of spade connectors, wires, etc as well. That way down the road adding a fused power distribution block will be an easy add on....

Looking at your print and checking the repair manual I've got, it seems to show the same - the ignition hot lead is on the right (as looking at the image) side of the solenoid and the "start" circuit is on the left side...looks like it should work, I'll break out the volt meter first. Thanks for the help guys!
 

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Ah yes I see, however you won't be getting a full 12 V. You will actually only be supplying something around 8 V to the choke.
 

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No, the choke will get the full battery voltage. The problem is that the relay is using power from the ignition circuit to close the points on the relay. This will reduce the power going to the coil when running. You are tapping voltage just as if you were running the relay right off the coil. This is NOT recommended. It takes power from the ignition circuit where it is needed especially at high rpm and/or high loads. Find a switched 12v supply for the relay.
 

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Bck to the original question............

Working with a 1967 Mustang, 289 C-code.

Folks have suggested hooking the trigger end of the relay to the STA terminal on the alternator - anyone have any experience with this? Any specific relays, or just any basic radio shack relay will do? I want something that will only trigger when the engine is on and running, not just at key on to avoid opening the choke if i'm listening to the radio or something while the car is off.
I read a lot about this before I hooked up the e-choke on my '65 -
I just crimped a connector on the end of the wire from the choke and hooked it to the STA terminal - simple but effective.
I have driven for a year like this - it works fine and I have never had any problems with it.
 

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Discussion Starter #13
Paul - I'm also putting an MSD 6AL Control Box and MSD Distributor in the car, so the coil will be powered through the MSD setup and not the old ignition circuit, I think this avoids the problem you are describing?

Cobra6 - from what I had been reading, the STA terminal only puts out around 8-9 Volts, which would heat the choke enough to open it, but more slowly than 12 V - but if it is working for you, it works! However, if I can drive the relay off the STA and have a straight 12V to the choke, then the choke circuit would only start heating when the car is actually running, and not when the key is in the ON position...I might try going this route, and set up a separate relay driven switched power circuit for any power hungry add-ons I may want to do...Amp, stereo, etc :) This way I can everything fused and isolated, with the only added power draw to other circuits in the car due to the relays

Thanks for the responses!
 

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Paul - I'm also putting an MSD 6AL Control Box and MSD Distributor in the car, so the coil will be powered through the MSD setup and not the old ignition circuit, I think this avoids the problem you are describing?
If you are going to use a MSD 6A or 6AL box you need to remove the pink resistor wire. If you power the MSD box with the 16A wire to the "I" terminal (8-9Volts) located on the starter relay, it will eventually cause the box to fail.
I ran a new 16 gauge wire from the back of my ignition switch terminal post (12Volts when in on position) to the "I" post and to the MSD box

Good Luck and BE Safe
Ron`
 

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Discussion Starter #15
Ron

Was planning on running the 16 (red/green) wire that used to run to the old coil into the MSD - or should i just try to run a new wire off the ignition directly?
 

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Discussion Starter #16
after looking at the wiring diagram some more, it looks like the wire from the ignition starts out as 16, turns into 16A after the resistor, goes into a wire harness and comes out as 16 again - meaning I will have the resistor issue you mentioned if I wire into 16 in the engine bay?
 

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I just noticed you have a 67. I have a 66 and am not sure if the wiring and numbers are the same so check to be sure.

The 16a wire on a 66 is pink and has internal resistance in it and is under the dash. It was easier for me to run a new circuit and not disturb the wiring under the dash. You can remove the plug connector and use that as your wiring point if you choose. I made a new penetration in the firewall and put a rubber grommet in to run the circuits. I think playing with the original fire wall main disconnect is asking for trouble because of the old wiring and connections.

You can also consider putting in a hidden kill switch for the MSD power. Might slow down a thief if they try to hot wire the car.

There are lots of ways to do it. I did mine so I could have lots of flexibility and I was not concerned about keeping it original (as you can tell by my ID :shigrin).

Good Luck and BE Safe
Ron
 

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Discussion Starter #18
The kill switch idea did cross my mind. I may wire in a couple spade connectors in line so I can add that in the future. Already have a few new holes in the firewall as it is, so I'll just route a new line out. I think we agree on both the flexibility and restomod approach :)

I've been double checking all your wiring diagrams against my 67 shop manual, no discrepancies so far!
 
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