On the starter solenoid or relay located on the passenger's side inner fender, does it matter which end the positive battery cable connects to, and which end the starter cable connects to?

It looks like this:

 

Don't think it matters. I've found them mounted upside down reversing sides. Just the "S" and "I" term needs to be correct.

 

Does anyone know why some models have this round starter relay instead? Is there a difference between the one below and the first one I posted that is more of a square shape?



This round one is the relay my truck came with, but the large terminals are just too close together. After nearly jumping out of my skin for about the third time this year because I accidentally bridged the two terminals and the starter began spinning, I would like to switch to the other style shown in my first picture. Will there be a problem doing that?

 

The photo in post 1 is the older style, better built I think.
I saw a you tube video of the inside of the newer style relay, I understand why they dont last long.
The "S" post goes toward the battery, "I" toward the starter. But it is just a relay and doesnt care about the direction of the curent flow thur the 2 big terminals.

 

???
The other one is round too, it just has a different bracket.

There is no polarity unless you purchase a Diode Suppressed version.

There is no problem switching to the older style solenoid that I've ever encountered.

 

Sorry, I don't know much about electricity. What does this mean?

I checked RockAuto, and it seems that the first relay I posted was used from 1979 - 1984.

The other style in the second picture was used from 1985 and up. I am not sure why the design was changed, but since my truck has a carburetor and Duraspark ignition, it should work fine on my truck.

Handling both of these relays, I can tell you that the one in the first picture (older style) is a bit heavier and more solid than the newer style.

 

Anybody know of a HD aftermarket replacement?? Or a good quality one?

 

Watch out for some of the newer models. At some point they did away with the "I" terminal. I think it was an 86 Ranger I was working on had that newer style.

 

You can get a Motorcraft one in the early style. I replaced the one on my 81 earlier
this year. The PN is SW-1507-B and E7HZ-11450-A. It cost me $26.87 which part
of is shipping charge.

 

Diodes can act as one way 'valves' or can be used to limit current, as a 'zener' diode does.

Diode suppressed solenoids keep the pulldown electromagnet of the solenoid from acting like an ignition coil and spiking voltage when the current is removed.

 

Here is a good picture with info.


Relays

"Quenching Diodes" are what they came them, same idea as a suppression.

I would not pay a lot extra for a starter solenoid with an extra "add on" 10 cent diode.
Jim

 

Diode suppressed relays actually tend to have shorter lives and more welding problems than conventional ones.
But if you have an RFI problem sometimes they are the solution.

I only mentioned them because Lariat asked if solenoids were polarity sensitive.

 

Does anything even connect to the "I" terminal on the 1980 - 1986 trucks? Nothing does on my truck. I know the 1979 and under trucks do, and I think that is why all of the replacement starter relays have both an "S" and an "I" terminal.

 

I have a 1986 f350 crew with a big block 460 and I have the older style. I think that ford used many Different ways to hook them up. My motor was parts form 76 and a 86 460 and its all factory

 

S is the signal terminal to trigger it and I is the ignition terminal to provide 12v to the coil for starting, at least thats how my 68 is wired with the old points system.
Keep in mind the I terminal will not trigger the relay and if installed backwards the I terminal will always be hot.