What is relay 174 in VW transporter?

Relay 174 in a VW Transporter van is responsible for controlling the Glow Plug system in Diesel engine models. The glow plugs heat up the air inside the cylinders, aiding in starting the engine during cold weather conditions. Relay 174 receives signals from the engine control unit (ECU) and supplies the necessary voltage to activate the glow plugs. Once the engine starts, the relay opens and turns off the glow plugs to prevent overheating.