Recently bought a 1979 Mazda RX7, first year slick top K3 paint code. All original. The starter however wasn't working. Replaced it and repaired a few wires, now when I put the battery terminals on it just starts spinning. it's getting a constant 12V. is this a bad solenoid or did i just wire it in wrong? Any help would be great or even a picture if you have one!

 

Could have wired it wrong, but also could be a bad solenoid. Pictures from your end would probably clarify the issue.

constant 12v should come in and attach to the solenoid side. I’m guessing you might have attached the constant 12v to the starter motor side.

the smaller gauge wire which attaches to the solenoid should have 0v, until you put the key in “start” then it will have 12v. If this has constant 12v, I’d investigate the ignition switch. But I’m also guessing the car has a clutch safety switch, so power shouldn’t make it to the solenoid if the clutch pedal isn’t pressed.

note I have a fc but 99% of starter systems operate the same way, even if the solenoid is mechanically separated from the starter.