I have a '71 F250 with the 360 and I am converting my current mechanical choke to an electric one and want to run a couple ideas by you guys to make sure I do this right the first time:

1. The thermistor wire that needs to be spliced in to a switched source - I was planning on tapping into one of the three wires from the ignition harness that is in the engine bay (the one that goes to the ignition coil, oil pressure switch and water temp sender)
2. I was planning to mount the thermistor at the block grounding bolt behind the alternator. Seems to me that it's close enough to the exhaust and everything that it should get sufficient heat from that, but wanted to see if there is a better place to mount it

 

Do you have a picture of this unit you are using?
I don't under stand how it gets hooked up and why I asked.
You CAN NOT use any of the sender (temp or oil) wires as they are not a full 12 volts and will throw off that gauge as they work off resistance to ground.
You CAN NOT use the coil wire as it should not be a full 12 volts also and any thing on that system will pull power from the coil = NOT GOOD.

I am guessing this needs a full 12 volts to work?
If so use a relay to pull 12v from the battery and use the ALT S lug to trigger the relay to the choke only gets power when the motor is running.
This is how aftermarket carbs should get 12v to the choke.

The 80-86 300 six motor from the factory is a heater asst. choke. It gets hot air for the exh. manifold but also gets 6 volts from the ALT S lug to help the choke open.
Because the ALT and manifolds only work when the motor is running the choke will not open if the key is left on but not running.
Dave ----

 

I like your relay idea. Not sure if the 6 volts at the ALT S terminal is enough to trip a relay though. Have you done this before? If so, what relay did you use?

 

so a relay like this one?
IRHAPSODY 12 V DC 120 Amp 4 Pin Heavy Duty Relay/Split Charge Relay Switch, 4 Terminal Relay

the instructions that came with the unit said to tie into the idle stop solenoid but mine doesn’t have a wires going to that so it just says to use a switched 12v source.

 

Come-on with the relay. If you can provide a constant voltage to a relay it will work for the choke. Too much thinking going on here. Kiss method.

 

Why not just run a wire from the back of the ign switch and be done.. sounds like your over thinking something that is so simple.. Relay for the choke

 

You guys did not read my post did you?
If the choke gets power ANY TIME the key is on but NOT THE MOTOR the choke will be opening or stay open.
Using the S lug from the ALT or an oil PSI switch as the trigger for the relay the choke ONLY gets power when the motor is running.
Now on the oil switch you could just run power through it and when running the switch closes sending power to the choke.
But as they say it's your truck do as you want.
Good luck
Dave ----

 

I’m all for keeping things simple, especially when it comes to wiring!

I guess I should revise the question to this: what’s the simplest way to provide switched 12v power to the new electric choke?

 

That is a 120 amp relay! I don't think you need one that HD. Just a good one used for lights will work.

The reason for the relay is you trigger it from some thing that only gets power when the motor is running like the S lug on the ALT but that is only like 6 volts and why you can't run a wire from it to choke.

You can use switched power when key on but if the motor is not running the choke will be opening.
Not good if the motor stalls and key left on and you are inside letting it warm up some. Now the choke is open and you can't start the truck.
Dave ----

 

THE CARBURETOR SHOP / Automatic chokes

Sorry to voice my opinion on the subject since I've never had an engine with a choke. Its always the first thing I remove, just simpler to tap the gas and fire it up, so...I offer my apologies to ya'll and will move on.

 

no worries man! We’re all friends here . I appreciate all input from people much more knowledgeable than I. I haven’t had a car with a choke in probably 20 years and I was just getting into cars back then so I still don’t know much about them, let alone converting one to electric.