Maybe. For over 10 years I've run a manual GP setup with a DIY harness and no metal strap. No alternator problems or GP failures.Keep the existing ballast resistor in the circuit. That's that big piece of twisted ziz-zag metal strap connecting the existing relay and the output terminal on the existing Glow Plug Controller module. If you wire direct, you will over voltage your glow plugs and take out your alternator should you rev the engine before cutting GP power ( ask me how I discovered that! ).