Description
Product Overview
The Online LED Store 12V 40A Relay is a rugged, panel‑mount device engineered for demanding automotive applications. Constructed with a waterproof enclosure and heavy‑duty 12AWG wiring, it offers a maximum switching current of 40 amps and a minimum voltage of 12 volts. The relay utilizes a Bosch‑style 5‑pin SPDT (Single Pole Double Throw) configuration, featuring brass contacts for superior conductivity and longevity. With an auto/manual operation mode, a wattage rating of 480 W, and a coil voltage of 12 V (up to 14 V max), this relay meets the stringent requirements of modern starter systems.
Usage
Designed for automotive starter replacement, this relay fits seamlessly into panel‑mount locations within engine bays, under‑hood control modules, and aftermarket performance kits. It is ideal for professional mechanics, automotive hobbyists, and fleet maintenance teams who need a dependable switching component for high‑current circuits such as starter motors, fuel pumps, and ignition systems. The clear wire color coding—black ground, red VDC, white trigger, yellow N/C, and blue N/O—simplifies installation and reduces wiring errors.

Why Choose Us
Online LED Store combines industry expertise with rigorous quality control to deliver components that exceed OEM standards. Each relay undergoes comprehensive testing for contact resistance, insulation integrity, and thermal performance. Our products are backed by a detailed user manual, responsive customer support, and a proven track record reflected in a 4.6‑star rating from over 1,400 verified buyers. Choosing this relay means investing in reliability, safety, and long‑term value.
Key Features
- High switching capacity: 40 A continuous, 480 W power handling
- Waterproof housing with heavy‑duty 12AWG wires for robust main contacts
- Bosch‑style 5‑pin SPDT design for versatile auto and manual control
- Clear wire color coding for quick, error‑free installation
- Comes in 1‑Pack and 5‑Pack options to suit project scale
FAQ
What is the difference between the auto and manual operation modes?
In auto mode the relay switches based on the voltage present at the trigger (86) terminal, while manual mode allows you to control the output directly via the N/O (87) and N/C (87a) contacts, giving flexibility for testing or custom circuits.
Can this relay be used in marine or off‑road applications?
Yes, the waterproof construction and corrosion‑resistant brass contacts make it suitable for harsh environments, including marine and off‑road vehicles, provided the mounting location remains within the specified voltage and current limits.
Is the relay compatible with 14 V systems?
The coil is rated for 12 V DC with a maximum of 14 V, so it can safely operate in standard automotive electrical systems that may see voltage spikes up to 14 V.
Do I need additional heat sinking for high‑current use?
For typical starter motor applications the relay’s internal design dissipates heat adequately. However, in continuous high‑load scenarios, adding a small heat sink or ensuring adequate airflow can extend lifespan.
What warranty does Online LED Store provide?
All relays come with a one‑year limited warranty covering manufacturing defects, and we offer a hassle‑free return policy within 30 days of purchase.




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