06 997 starter weirdness

[87m491]

A friend with said 997, manual, was having intermittent no crank issues. Usually when hot. He went down a rabbit hole and ended up replacing the main positive line from the battery to the starter/alt.

This seemed to help a bit but the car is very sparingly driven so hard to tell. Fast forward 6 months to last week when the car again refused to crank, but in the driveway.
In addition to no crank, there seemed to be a fan noise coming from the engine bay, no key on or in the ignition.

To keep the battery from draining it was disconnected, noise stopped. We pulled the starter and it bench tested fine as did the solenoid. We reinstalled the starter and as soon as the battery was reconnected, (no key in the ignition) the whirring noise returned. The noise turned out to be the starter spinning, yet the solenoid Bendix was not engaged/ing!

Weird. As the starter relay checked out OK, this seemed to point to the ignition switch sending a signal to the solenoid. Somehow getting through the solenoid without engaging the Bendix and spinning the starter. So, we remove the ignition switch to swap it out. For information sake, we reconnect the battery, with ignition switch uninstalled and the starter beginning spinning again!

Looking for the schematic for the car now but in the mean time and BTDTs?

Thx
Mike

UPDATE, checked the relays and even with starter relay pulled, the starter is spinning. I think it must be picking up power downstream from the ignition switch and relay to the solenoid.
Unfortubnately I can not find a scheamtic for that circuit to find the source of the non 12V+ wires to the starter.

[87m491]

Despite bench testing OK, The solenoid had welded itself closed so the starter was being back fed from the Batt + cable each time we reconnected it.

Problem solved.