Starter solenoid + post size/threading?

[OfficeMonkey]

I've been prepping to replace my alternator over the last week and change -- but this evening I discovered that the problem may be simpler (I'm still upgrading, just... maybe in the off season).

I discovered tonight that there's a missing nut on the starter solenoid -- specifically on the + Battery terminal. So the o rings are all over the connection, but none of them are held in place. The alternator may still be a problem -- but does anyone know what washer/nut is expected to be on there?

[joe_db]

I've been prepping to replace my alternator over the last week and change -- but this evening I discovered that the problem may be simpler (I'm still upgrading, just... maybe in the off season).

I discovered tonight that there's a missing nut on the starter solenoid -- specifically on the + Battery terminal. So the o rings are all over the connection, but none of them are held in place. The alternator may still be a problem -- but does anyone know what washer/nut is expected to be on there?

You would want a flat washer over the lug(s) and then a lock washer under the nut.

[OfficeMonkey]

Coming back in case it helps anyone else:
Starter solenoid is a Delco 969. Battery post is a 3/8" x 16 threading.

I added the flat washer and a lock washer, and tightened on a new nut.

I discovered the previous owner had used a M10 x 1.5 nut (fits over but wiggles) and then secured it with red threadlocker. I could not get the threadlocker off, but the additional space taken up by the flat and lock washer might it snug.

Also, WHY did they use the wrong nut??