Diagram and photos of high-current starter relays and solenoids

Starter Relays
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The top 2 (late style) (E9TZ-11450-B) use parallel bolts as terminals, so the copper washer inside always touches the flat bolt heads. The others (early style) (E9TZ-11450-B) use bolts perpendicular to the relay's axis, so the washer touches the sides of the bolt heads. But if the bolt is accidentally rotated (as during overtorquing), the washer will only touch a corner, causing high resistance, arcing, and welding. That's why the new style is far superior. All have 3~5 Ohms & draw 3~5 Amps.

The 85A continuous-duty relay has a metal housing to dissipate the heat, and its S2 terminal allows its coil to be fully isolated (for reverse-polarity duty). It has ~18 Ohms & draws ~0.6 A .
45A solid-state relay
200A continuous-duty relay
500A continuous-duty relay

Note that all Main terminals are electrically interchangeable. But on the newer relays, they are mechanically different in that the plastic housing restricts access to M2 slightly more, indicating that it should have only 1 wire attached.

It's common for these to be MISidentified as "solenoids", but a solenoid operates a mechanism, and a starter solenoid is ON the starter; a relay is an electrical switch. Many '90-up Fords have both a starter solenoid & a starter relay, so it's important to differentiate them.

A winch relay has 4 main terminals; 2 normally open, and 2 others normally closed.

See also:
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Owner caption July 2010 · Photo 3156 of 5000