Exactly what is clicking? Does the starter click (coming from under the hood), or is it just some relays in the dash that are clicking?

An intermittent starter solenoid (which wouldn't be too far-fetched on a car of this age) could be a problem. The contacts can corrode or wear out which results in a click but no juice to the motor. In this case you would hear a click from the starter but it won't turn the engine. But you say your "mechanic" has already changed the starter.

With a manual trans there are no safety switches. The key switch is probably not a problem if you hear clicking as a result of turning to position III. Maybe there is a problem with the wiring between the key switch and the starter. Has your engine/ignition wire harness been replaced? The starter wire going thru the grey box at the firewall is one of those that is especially susceptible to insulation rot. There may also be corrosion in the grey box causing intermittent contact.

Knowing exactly where the clicking is coming from would be very useful information.

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Matt L. -- Cary, NC -- '89 740 sedan -- '91 740 wagon