Starter relay options

[kevindeluca66]

I know I haven't been here in a while but kids and sports are consuming my life right now. Anyway I have been having starting problems on my 66 with 428 in which all I hear is a click when I turn the key. I have replaced the starter and the relay several times this year. I've also encountered a situation where I let off the key and the starter continues to crank the engine until I can get the negative battery cable disconnected. I do this with a green knob battery switch. I have used several brands of relays over the years as I have changed it about 6 times in the 19 years of ownership (funny, today is my ownership anniversary, lol) and have used Car Quest, Napa, FoMoCo. and Auto zone. All of these have failed, some sooner than others.

My question to you all is what brand and part number are you using.

Or another question is am I missing something else to check?

[Rusty57]

It is interesting that you have had to replace that many relays. You might try some other troubleshooting steps to isolate the problem.

I know this sounds crazy but I wonder if the problem is in the ignition switch. Contacts wear over time but also get corroded. They also transfer material from one contact to the other because in a direct current system the spark always jumps the same direction. That is why one ignition point gets pitted and the other gets a small projection built-up on it.

In some cases that corrosion reduces the current going through the contacts. So there might not be enough “juice” to make the relay close properly. In other cases the contacts might not release when you move the key from start back to run. So the relay stay energized.

Here are some simple tests.

Do you ever get the “click” when you jumper from the 12 volt feed post on the relay to the start terminal? That test eliminates the ignition switch from the start circuit.

Disconnect the wire from the starter terminal on the relay. Do you get a 12 volt signal to that wire whenever you turn the key to start? Is that voltage lower than 12 volts?

What happens if you remove the wire from the starter terminal on the relay if the starter keeps running. That should disconnect the current from the solenoid in the relay. So the relay should disconnect.

Just some ideas. Tracking down electrical gremlins can be frustrating.

[David Langhorne]

Hi Kevin, I doubt the problem is the ignition switch but you can easily test it. Pull the wire off the S terminal on the relay and connect it to earth via a meter or better still a 12V bulb. You can then sit in the car and turn the key over and over and see if the light stays on. My guess is it won't.
I have had this problem a number of times and it has been down to low battery voltage or poor earth from the engine to the battery. I looked this up a few years back and it seems electric motors will draw more amps to compensate for lower voltage and it is the extra amps which overheat the terminals in the relay and cause them to fuse together momentarily. You could have a bad connection in a number of places such as the engine earth strap to the chassis rail or a bad battery lead which I had and took me ages to figure it out. You may find a bad earth by touching all the wires and see if they are getting hot just after cranking. You can repair the relay by drilling out the rivets and cleaning the contacts and reassembling with nuts and bolts. Of course it may be you have just been unlucky with relays and starter motors.....

[DakotaLee]

I had this exact issue. It wouldn't go away no matter what until I got a vintage US made relay.
I went through no less than 5 store-bought overseas relays. Burned through them all. First non-cheapo OEM one I put in has been fine with no trouble ever since. A trick you can use if this happens to you again (so you don't have to remove the battery cable) is you can just hit the body of the solenoid with something like a wrench and it'll free it up. Percussive maintenance.

[kevindeluca66]

Thanks guys for the advice. I'm going to start with Davids advice and check ground connections underneath first and order a new relay. I still think it's a relay issue only because when I switch relays, I get different results but a bad ground somewhere may effect different relays in different ways.
Question for Dakota Lee and everyone for that matter is what part number relay are you running with. I have seen some with a FoMoCo 2701966 number and also a Motorcraft # D2AF-11450-AA. Does anyone know the difference between these or what belongs on a 66 with a 428 so I can get something ordered.

[DakotaLee]

Thanks guys for the advice. I'm going to start with Davids advice and check ground connections underneath first and order a new relay. I still think it's a relay issue only because when I switch relays, I get different results but a bad ground somewhere may effect different relays in different ways.
Question for Dakota Lee and everyone for that matter is what part number relay are you running with. I have seen some with a FoMoCo 2701966 number and also a Motorcraft # D2AF-11450-AA. Does anyone know the difference between these or what belongs on a 66 with a 428 so I can get something ordered.

I would recommend Motorcraft SW-7663 if you're going with a new part. Your FoMoCo number also is good. I don't recall what I am currently running on my 66, but I believe it's a Motorcraft.

[kevindeluca66]

I have another first that I saw a a recent car show. The attached picture is a 66 with 390 and a separate junction block of sorts that the three wires that attach to the positive battery cable side of the relay. Has anyone else ever seen this. I couldn't find the owner of the car but I have talked to her several years ago. I don't have a picture but this car also has a unique setup for the hood to radiator support seal in which the seal and bracket are mounted to the radiator support similar to a rocket bird. If it's not original then it sure looks old. I have studied 66 Birds for a long time and never seen it before. Maybe it's a 390 thing. My mom's original owner 428 convertible doesn't have it.

https://photos.app.goo.gl/iWeJ6cx2dX3E65af6

I'm still debating which relay to go with next.

[Scott6T6]

Hi Kevin, I absolutely agree with what others have already said here. Forget about ANY aftermarket starter relay, they are NOT reliable. You'll be wasting your money and experience nothing but aggravation if you elect to go with the aftermarket part. I've heard this sentiment echoed time after time with owners of any model of vintage Ford from Falcon's to Thunderbird's.
Stick with the genuine Ford units. The Motorcraft D2AF-11450-AA (SW3) relay is of course a later service part, but it will work just fine.
If you want to keep it factory correct you would need to find the FoMoCo 2701966 unit - rectangular FoMoCo logo is factory correct for '66. This will of course be much tougher to come by than the Motorcraft part and it will cost considerably more, but that is one you need if factory correctness is important to you.

I have the original factory installed FoMoCo starter relay in my '66 and it still functions perfectly after 55 years!

Scott

[Rt.146]

The consensus from what I hear. starter relays are frequent replacements, got me thinking, one of the reason I find may just be the China knockoffs, at Around $20.00, compare to a Motorcraft made in the USA for around $34.00. I have bought several of the knockoffs same old same old performance, I switched to the Motorcraft, time will tell if it works out better.,

[sleeper bird]

bet the ignition switch is the problem.iv had the same issue as you twice and it was ignition switch both times.twice in 8-10 years