How to Wire a Relay for an Electronic Choke 

Wow, thanks! I appreciate the feedback as sometimes this work seems so one-sided. :)

You're welcome!

My pleasure!

Happy to help!

Glad to help! Welcome to the club!

It might fall under “do as I say, not as I do”? 😄

I think it is too, but others see it as a waste of time. It is agreed that the coil for the electric choke pulls a very small amount of amperage to the point where it can piggy-back on another circuit, I like having a dedicated circuit for additions to the car so I can track things down if there's a problem. :)

Awesome, I appreciate the feedback. Good luck on your build, hopefully you'll get just the info you need! :)

Trust me, there's plenty of clever editing going on here. :)

@@AndyKruseChannel I just rolled all 4 fenders...what a tedious task!

@@nathannelson7020 Rolling the fenders is another great source of all the bad words we're not allowed to say. :)

Thanks!

Thanks 👍

Awesome! :)

Thanks!

Headers are coming soon (keep an eye out for that video), but I'm not sure yet on the Rad. The main reason I replaced it on my last Mustang was because it was leaking. So far this Rad is doing great and I'd rather put my money towards other parts that need some love first. However, I will eventually replace it as I'd like to go to an electric fan setup, possibly a dual fan option. The stock Rad is not larger enough for dual electric fans, but my engine is doing great on the stock setup, so........ :)

This is good advice, and I've done that in the past. However, when I did this video, I just used what I had in the garage. :)

I like using the shrink wrap too, I’m just out of the size for this wiring, I need to buy some more. 😁

Correct, the power source for an electric choke is only hot when the car is on (as I've done here). And yes, by feeding that choke a 12V signal while the car is on will keep the choke open during the use of the car, and it will begin to close once the car is off. However, due to the nature of the coil inside the electric choke, the a hot motor and a hot day will make the choke stay open, but it may not be fully open, which could cause a little havoc with the driver if the choke is closing while they're headed down the road. To reply to your comment about the choke always being 'on' with a power wire that is active while the car is on, this is fine and it does not cause any electrical issues or wear out the choke. The amperage draw of the choke is low, and this is how all cars of the era (and for quite some time later) were wired up. I guess someone could wire up a switch that cuts power to the choke once the engine is warmed up, but that choke needs to remain open during the drive, so it's easier to just feed it a 12V switched source and call it a day. :)

To be clear in my mind, my choke only has a connection for the hot wire. I was told when I got the carb to just run a hot wire to the fuse box with a fused line. It’s a 75 Chevy. I think it’s grounded in itself. But, is it ok to wire it to the fuse box without using a relay like you did.? Plus my solenoid is on the starter, not the firewall. Thanks so much

I don’t want it staying ‘hot’ powered, after the engine warms up if this isn’t good.

Just a standard automotive 10A fuse, way more than is needed, this electric choke doesn't pull much juice. :)

I have read that it's not ideal to tap into the coil for what I am doing with that electric choke. This way I get a dedicated power source and nothing in the car is affected by this circuit. :)

The coil isn’t a constant 12v and you don’t want to draw any current away from your ignition.

Welcome! To be honest I don't know if the solenoid is internally resisted. Back when I made that video, I was looking for 12V switched sources in the engine bay so I didn't have to run a wire from under the dash. :)

Thanks for the heads up.

Correct, 12v fuse, 10A is plenty. Some people prefer the control of a manual choke, but I'd rather have an electronic version so I don't have to mess with it. :)

Thanks for the heads up.

Thanks! 10A is more than enough, the choke doesn't take much juice. :)

@@AndyKruseChannel i came to find out i don't even wires from my choke, your older video seems to connect directly to the alternator? Or should I follow this latest one that taps to the solenoid? Thanks for replying btw

@@pinoypostman4648 Using the "I" terminal on the starter solenoid just give you a switched source (hot when the car is on) to trigger the relay. This saves a step from putting a wire on the back side of the ignition switch for essentially the same thing. The "I" terminal is only keeping the relay on when the car is on, but the power to the choke is coming from the battery through the relay. :)

I put a 600 on my 289, but it was too much. A 500 or 570 would be sufficient for there motors. As far as replacing the 2100, it's a great carb, but you're leaving some performance on the table with that 2 barrel. While you can buy an adapter for mating a 4-barrel carb to your 2-barrel manifold, it'd be a great time to upgrade that too, but it just adds to the bill. :)

It could be a number of things. Without knowing the state of your carb, it could be a setting, a stuck throttle, clogged jets, sticky float, improperly set choke, bad gas, etc. It may be as simple as redoing the idle mixture screws on the front of the carb. I recently did a video on how to adjust them, give a watch and see if you can fix your idle with that video. :)

Yeah, there are lots of good uses for relays, but they're not for everyone. :)

Working from the beginning of your post, you are correct, the voltmeter should read zero at pin 87 when the car is off. If you connected pin 86 to the "I" terminal of the starter solenoid, and the car is off, the voltage at pin 87 needs to be zero. Pin 87 will only show 12V when the car is on (running or just with the key in the 'on' position). Moving the voltmeter to pin 87a at this point should give you 12V (as you pointed out), but this is ok because you are not using 87a and it should be taped off (like I did in the video). Now this is where it gets tricky because it sounds like you just turned the key to 'off' and the voltage at 87a went to zero. It should still say 12V as pin 30 should be attached to the battery, or at least a constant 12V source, regardless if the key is on or off. The choke can get 12V during the whole time the car is on, even after the choke is fully open, it's not hurting anything. Some people skip the whole process of the relay and just wire up the choke with a switched source (a voltage source that gets 12V only when the car is on) and it works fine. I like relays and I like isolating the various circuits on additional electrical components. It's a tiny bit overkill on this car, but I like having a dedicated circuit for the Choke. Hopefully this helps! :)

I needed a 12V source that was only on when the car was on. Plus, I didn't want it tapped into anything else that was running in the car, I wanted a dedicated power source. There are a few places in the car that one could tap into for a switched source, but this way guaranteed me the power I needed without interrupting anything else.

You can just hooked up to the coil.

@@brechtvancauwenberghe9440 Yup

That's not how that works, the relay is on when the engine is running. You are more than welcome to grab a hot signal from the alternator, or the back of the ignition switch, I just chose this location be cause it's simple and it works. :)

@@AndyKruseChannel -- You are gabbing power from the small right side terminal [ the Ign. terminal] on the Ford starter solenoid to signal the relay, to turn the relay on, so power flows from the large left side BAT terminal through the relay to the choke heater coil, correct? This is what I got from your drawing.

Switched power is coming from the ignition switch (in the dash) when the key is on and it goes to two places off the same wire when it passes through the firewall. One of the places is the positive terminal of the ignition coil. The other place is the ignition terminal (labeled "I") on the starter solenoid. Pulling power off that terminal to activate my relay is the same as either tapping into the red/green wire coming off the ignition switch, it's just easier to grab the 12V at the "I" terminal. Admittedly, the relay is already overkill for this application, but I like it. :)

Yes, other wise that bi-metal coil will cool down and the choke will begin to close. The old heat-tube style choke systems that were stock on these cars ran off the heat generated by the exhaust, which kept that coil warm and in turn kept the choke open.

@@AndyKruseChannel thanks Andy.

@@AndyKruseChannelquestion if you don’t mind answering, is there any downside to running an electric choke that way?

@@noble5856 Running it which way? Are you asking if there's a downside to powering the electric choke with a constant source? Without the constant 12V source, the coil inside the choke will cool and close the choke. The choke must be powered the whole time the engine is running. The same applies to the heat-tube style of the original choke, it receives a constant source of heat while the engine is running, keeping the coil in an expanded state, which keeps the choke open. After the engine turns off, the heat is no longer applied, the coil moves back into its "cold" configuration, and the choke closes for the next time the engine is fired up. In the summer time the coil likely stays warm with the warm outside temp, but that's ok because that means the engine is sort-of warm and the choke is not likely to be needed. :)

@@AndyKruseChannel I thought the I could use the old style of electric choke from the old carb with heated coil but it seems like it the carb isn’t built compatible with that I didn’t want to add any extra wires to the engine bay, I appreciate you explaining the differences though, your channel is great and very helpful

I think it's a 15A fuse in there right now, but I might bump that down to 10A. Not sure about the relay number, but I did get it off ebay in a pack of 5. This is a normally-closed relay.

Thanks!

I'm sure there are lots of ways to wire up the electronic choke, I just landed on this one. I don't know what starter solenoid you have, it's possible yours is different. I wanted an isolated circuit, it is common to use relays to trigger various devices and components, and I wanted to do that here.

The stator voltage is only about 9 volts and Holley choke heating elements need 12 volts at about 10 - 15 amps. Using the Stator voltage significantly prolongs the heating up of the chole element, making the chole stay on longer. I believe that the OEM Ford choke elements needed only about 9 volts to power the heating element/

10A is more than enough, a 7.5 or 5A fuse would work too. I just used what I had in the garage. 😁

Haha, I wanted to but I didn't have enough spare wire to match the colors. :)

The wire that triggers the relay is the wire that goes to the ignition coil (I think it's brown?). However, some cars don't use that terminal, specifically if your car does not have a resistor wire as part of the ignition coil. You may be able to tap into the back of the ignition switch in your dash for a "switched" source. I think the red wire with a green stripe might be what you're looking for.

@@AndyKruseChannel unless I'm getting a significant voltage drop from the ignition to the starter solenoid I'm only getting 5.8v and the terminal do you know what voltage your getting at the solenoid

@@rydred0823 You should have around 12v there, not sure why you're getting 5.8v if the car is running.

Same here. The stud marked with the I on the solenoid is down around 6v. Car does run. Mine is a 67 Mercury Cougar with 289.

Your relay may not have the same colored wires for the various terminals as mine.

@@AndyKruseChannel hi Andy well I ordered what I thought was the same colored wire harness do you mind if I send you the pics

@@75cezr The wire color is not important, but you should be able to follow the diagram in the video based on the terminal number. For me, the red wire goes from terminal 87 (referred to as "normally open") to the choke, so you'll want to make sure that terminal 87 on your relay is doing the same thing. While you're there, double check all the other terminals are going to the correct location based on that diagram. :)

@@AndyKruseChannel thanks andy

If you know it's over kill then why did you watch the video? I think you didn't because I explain that it's overkill and why I chose to install one anyway.

Different strokes for different folks.

I think it was eBay, it’s just a generic automotive relay harness.

It’s a weight-saving technique! 😜

I like my circuits to be isolated, so if there is a problem, I can narrow down where the problem might be. However, the amperage pulled by the electric choke is very small, so realistically pulling a 12V switched source from pretty much anywhere would be sufficient here. 🙂

I don't know if the wire color on my relay was standard, the red wire is the wire that gets electricity when the coil in the relay is activated. The white wire is the ground for the coil. Connecting the white wire to the electric choke would not provide the desired results. Further, the black wire on my relay is terminal no. 30, this is the wire that needs to be connected to the 12V source. I guess I could flip the red and black wires and still achieve the same results, but I cannot swap the red wire with the white wire. Again, this applies for the wire harness that came with my relay. I provided a diagram in the video showing the wiring layout just in case someone had a different harness, but could use the same numbered terminals that I did.

To make it more fun. :)

The carb, heads, manifold, block, and firewall are all metal and connected, and the block is already grounded to the firewall. Because of that, grounding it to the carb is sufficient. It is incredibly common for people to ground the electronic choke to the carb like I've done here. Now, adding a relay for the hot wire for the choke is a little overkill, but it's what I wanted. :)

I think I have a 7.5A fuse in there, it was the smallest I had in my garage. This system draws so little amperage that a 5A fuse would still be overkill. :)

Ideally the Choke is on its own 12V, and not pulling off something like the Coil or other circuit that is in use. The Choke doesn't draw much current, but if you're in the position to have a dedicated circuit, it's better. Also, the relay allows the Choke to pull a full 12V from the battery and it can be triggered by anything that is on when the car is on. In this case, the ignition terminal on the Starter Solenoid is active when the car is on. That terminal is putting out a 12V signal, but it pulses (based off the Coil) and is not an ideal source of electricity for the Choke. But it's good enough to active the relay and allowing the Choke to grab a good 12V from the battery. :)

I explained why I chose to use a relay in the video. :)

Are you asking where to pull the signal wire from to trigger the relay? Otherwise, wiring up a relay to power the electric choke on other vehicles would essentially be the same as this.

There are lots of ways to wire up the choke, I wanted my setup on a dedicated circuit so it's easy to find electrical issues if I have them. :)

Thanks for the advice.

I explain it in the video.

You do know that aluminum is conductive, right?

...And conducts better than steel.

Yep.

@@AndyKruseChannel was reading some of the comments & FORD did use a relay for their electric choke for the Holley 4180c four barrel carburetor found on the 84-85 Ford trucks with the 351 H.O engine . The choke relay was mounted on the firewall near the brake booster .

Agreed, relays are more useful for components that need higher current, but it serves it's function.

Disagree bud. I'm actually having that issue. I'm running an electric fan and it draws way to much power so my fan do kick on. It goes from 12v to 9v.

I followed Andy's video and it works. Plus side of it is that the choke has a heated coil so if the choke fails and just so happens to draw an excess amount of current its a failsafe precaution for $10.

Respectfully, I disagree. While your suggestion would work, having a dedicated 12V source to the choke keeps the amperage draw at a minimum running through the ignition. Yes, more wires can create more issues, but if someone does it correctly and in a manner that makes sense, tracking down issues becomes an easy task. In this case, if the electric choke was not working correctly, one does not need to mess around in the dash to find the issue as everything is in the engine bay and located in a small area.

JUST USE THE ING. COIL 12 V. +. ONLY 12 V. WITH KEY ON KEY OFF NO 12V. TO COIL. & USING BUTT CON. THATS BEING HALF ASS WORK !!!

@@AndyKruseChannel no that is not true the ignition switch has a dedicated accessory post for a reason when you try to crank the engine the voltage will go away so you don't have a draw on any accessory you have. The ignition switch has a battery wire a number 8 or 10 guage depending so when you start the engine you will have between 14 to 14.5 volts going to the electric choke. If you're charging system is working right you should be able to turn on your heater blower motor your head light's wipers and anything else and the alternator should still put out between 14 and 14.5 volts. And you do not ever connect another wire to your coil your coil needs at least 9 volts to work properly and if you do you will have a voltage drop when starting the engine. I have been doing this kind of work since the late 60s I owed a chassis shop for over 20 years and built race engine's I just retired.what might your credentials be.

And by the way if you had a problem you only have one wire to trace the one you ran to the electric choke and you should put a fuse in the wire to eliminate that problem and if you blow a fuse check your electric choke for a problem.

Wrong, ING. Side of key switch, acc. Is for radio. If wire to acc. No power to choke.