Starter Solenoid - Suppression Diode?

I got some feedback from a mechanic that the starter solenoid had some stripped threads (thanks, PO!) and should be replaced.

Ok, easy peasy, no problem.  I order one from RockAuto.  Then, I missed a warning on the page (paraphrasing here) "Do not use this solenoid on a vehicle with an EEC - your EEC will be damaged, your wife will leave you, your dog and cat will start dating, etc"

Ok, fine.  I go on Napa, and order one from there that looks a little beefier anyway.  I get it in the mail - first thing, the same warning on a bright yellow piece of paper.

So, I learn that the original solenoids have a diode to suppress leaky voltage coming back to the EEC when the solenoid disengages.  The trick is, I can't find a solenoid that advertises to have a suppression diode.

My existing solenoid is a 3 terminal (no "I") on it.  I also looked in the EVTM and there is a diode inline perhaps (see below) but I'm not confident looking at just the diagram (not the schematic) that the diode is for the solenoid.  I also don't seem to have the G756 connector.




Is there an inline diode in the wiring harness somewhere, or where can I find the right solenoid?  Hopefully I have stated the problem well enough.

Chris, you can get a 3 terminal diode suppressed "Ford/Motorcraft" style relay here:. https://www.maniacelectricmotors.com/66001044.html
Maniac offered excellent service when I used them for starter and alternator parts.

Texas Industrial Electric shows it as #15-450, Motorcraft SW1951B-&-C  or Prestolite SAZ4201EA.
They have the best selection of automotive/industrial switching devices I've found on the web.

I'm not sure why the illustration in the EVTM shows an auxiliary ground to the relay mounting tab.
I've never seen that before but it certainly couldn't hurt.

Thanks for the links Jim!  Good to know there is a source for these.

Seems like something to not experiment with, you know?

I hear you!   👂

Having the diode incorporated into the relay makes a lot of sense.
Best practices, and all...
.
Do you know where the other end of that ground wire goes? I don't have the EVTM in front of me...
It seems tucked down behind the battery from what I can gather with the pic zoomed as big as my phone will go.
Your battery ground terminal should have a pigtail that meets and grounds the ecu at the radiator support.
Easy enough to make up a jumper with two eyelets to attach from there to the relay grounding ears.

Also look WAY down the Texas Industrial Electric page under intermittent duty / momentary relays at  #7--1035 for a $17 option said to be used on "later Ford products. SW1951 (with no suffix) can replace 15-450."

I didn't notice it at first because I didn't bother to look farther once I saw the first listing.  

First of all, Merry Christmas!

I just got the new solenoid in the mail from Maniac (https://www.maniacelectricmotors.com/66001044.html).  There are no directions, and no markings on the solenoid.

I have a 50/50 shot, but how badly will things go if I hook the positive cable up to the wrong side?

Here is a picture of my existing solenoid, just as an FYI (this is an old picture). Obviously the new one looks different, but I'm not worried about that as long as there isn't some tidbit I'm not aware of regarding functionality.  The ears on the new solenoid look like they'll be in the right spot for the existing fender screw holes, etc...

Hi Chris.
It seems you got prompt service from Maniac, as I have.  

It doesn't really matter which way the battery and starter cables go.
But you will find continuity between the S terminal and the mounting plate should only go one way in diode test mode. (Ohms mode may not load it enough)
This prevents an inductive spike from killing the front end transistors in the EEC.

When you get it mounted to the fander just attach battery and all fusible links to the forward stud and the starter cable to the reward side.
Edit: from the photo on their page I would say connect the battery to the stud with the nut unscrewed.

I think vehicles with EEC used a different style of starter relay:




Lucille came with a feedback carburetor and EEC-IV controls, and she originally had the style on the right.  Every Ford I have seen with EFI also used that one.  Whereas older carbureted vehicles without EEC used the style on the left.

Perhaps the newer style (on the right) has the suppression diode?
 

That was my theory. I got a little confused as I looked at pictures of 84s with 302s, and they had the solenoid on the left. It didn’t occur to me that they weren’t EEC equipped though.

I’ll put the new solenoid on today or tomorrow. I found some examples on the web about how the wires would typically be installed ignoring the I terminal):

Dang message rotation. Sorry.

Thanks Jim!  Gonna try it today or tomorrow. Hope you’re having a good holiday and staying warm.  

Not to be a jerk but it’s 80 here. I wish it was somewhere between this and the eastern half of the country!

That whole coastal area west of LA (Malibu, Ventura, Santa Barbara) seems to have a beautiful climate.  
I'm glad you can enjoy it!

Thankfully here on the Long island Sound we've been spared the brunt of the snow and subzero weather.
Lots of wind and rain Thurs and Friday with power outages but the cold was only down to single digits and it's up in the teens today.
Winter just started. We have a couple of months of cold and snow to come here in the northeast

It is very nice here.  I grew up here, so I am a bit spoiled - you pay for the real estate though (and draconian smog laws, don't get me started)...

Just following up, I got the solenoid installed and all is well!  Thank you for all your help and advice.