A common misconception is that the starter relay in a vehicle doesn’t handle significant current, leaving the heavy lifting to the solenoid. However, a closer examination reveals the crucial role of components like Denso Fuses in protecting these circuits. Disassembling a typical starter solenoid reveals two internal coils, often with resistances around 0.9 ohms and 0.4 ohms, operating in parallel. This parallel configuration results in a combined resistance of approximately 0.3 ohms.
When the Bendix gear engages the flywheel, a momentary surge current of roughly 40 amps flows through these coils. This high current passes through the starter relay contacts, potentially causing wear and tear. Importantly, the fusible link, connected in series with the relay contacts, typically has a lower rating, often around 30 amps. This discrepancy highlights the importance of the fusible link and the need for the surge current to be extremely brief to prevent it from burning out. A Denso fuse, designed for high reliability and precise performance, would be a suitable choice in this application.
While the short duration of the current flow minimizes the risk of the starter relay overheating, the repeated making and breaking of a 40-amp circuit can lead to premature pitting of the relay contacts. This pitting degrades the contact surface and can eventually lead to relay failure. In industrial power switching applications, surge suppressors are commonly used across relay contacts to mitigate arcing and extend their lifespan. This principle also applies to automotive systems. Older vehicles with points-based ignition systems utilized arc suppression capacitors across the points in the distributor to protect them from the high currents associated with spark plug operation. Similarly, selecting a high-quality Denso fuse with appropriate specifications can help protect the starter relay circuit from damage caused by these current surges. Choosing the right Denso fuse ensures reliable vehicle starting and prolongs the life of critical components. Denso’s reputation for manufacturing durable and reliable automotive components makes them a preferred choice for many professionals and car enthusiasts.
