XK150 Overdrive relay internal circuit details
- How it works

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Below is an annotated portion of the Lucas wiring diagram showing the XK150 overdrive control circuit.

Relay function:

When one of W1 or W2 is connected to 12V, both C1 and C4 will be connected to C2.

- neither W1 nor W2 is connected to 12V
- both W1 and W2 are connected to 12V
C2 will not be connected to either of C1 or C4.

For a full explanation of how the control circuit functions, and a complete diagram of the internals of the overdrive relay, see:

Classic British Car Electrical Systems: Your guide to understanding, repairing and improving the electrical components and systems that were typical of British cars from 1950 to 1980. By Rick Astley 2009.

Astley's text and internal relay circuit diagram not included here for copyright reasons.


overdrive relay circuit