This is a sealed automotive 40 A relay in 4-pin or 5-pin SPST/SPDT format, rated for 12 V or 24 V coil duty, designed for fog lights, headlights, fan controllers, fuel pump control, A/C compressors, and any high-current 12 V or 24 V automotive load that exceeds the capacity of the vehicle's switch contacts. Silver alloy contacts, 100,000 electrical cycles, 10,000,000 mechanical cycles, copper coil. CE certified.
Product Description
This is an electromagnetic automotive relay in the standard ISO 280 footprint, supplied in 4-pin (SPST normally-open) or 5-pin (SPDT changeover) variants and matched to either a 12 V or 24 V coil. The function of an automotive relay is to let a low-current switch (e.g. a dashboard toggle, a horn button, an ECU output line) control a much higher-current load (a horn, a starter motor, a headlight bank, a cooling fan) without overloading the switch contacts. Routing the heavy current through the relay's silver-alloy contacts keeps the wiring loom safe and the dashboard switch lasting longer.
Specifications: 40 A operating contact current, copper coil, sealed body for environmental protection from dust and splash, silver-alloy contact material that resists arcing-induced erosion, and a service life of 100,000 electrical operations under full load (with the mechanical cycle life ten times higher at 10,000,000 cycles). The body is sealed for use in engine bay environments where road spray and engine heat are typical.
Key Benefits
- 40 A rated contact current handles fog lights, headlights, fans, fuel pumps, and A/C compressors
- Silver alloy contacts resist arc erosion under repeated switching of inductive loads
- Sealed body protects against road spray, engine bay vibration, and dust ingress
- 4-pin (SPST) and 5-pin (SPDT) options cover both simple on/off and changeover wiring
- Both 12 V and 24 V coil variants — one product line covers cars and commercial vehicles
Key Features
The defining feature is the contact-and-coil pairing engineered for automotive duty. Silver alloy contacts handle the high inrush current of inductive automotive loads (motors, fan windings, lamp filaments) without welding shut, and the copper coil provides reliable activation across the full operating temperature range of an engine bay. The 5-pin SPDT variant gives you a normally-open and normally-closed contact in one package, useful for circuits where you need to switch one load on while breaking another (e.g. activating high-beam while breaking the low-beam circuit).
Technical Specifications
The defining parameters are the 40 A contact rating, the silver alloy contact material, and the choice between 4-pin SPST and 5-pin SPDT configurations. Full specs below.
| Parameter | Value |
|---|---|
| Contact configuration | 4-pin SPST normally open, OR 5-pin SPDT changeover (selectable per variant) |
| Coil voltage | 12 V DC or 24 V DC (selectable per variant) |
| Operating contact current | 40 A continuous |
| Contact material | Silver alloy |
| Coil material | Copper |
| Body | Sealed, black plastic housing |
| Electrical life | 100,000 operations at rated load |
| Mechanical life | 10,000,000 operations |
| Footprint | ISO 280 standard automotive relay |
| Compliance | CE certified |
| Internal SKU | 54G-RLY-AUTO-001 |
Technical data sourced from manufacturer documentation.
What's Included
- 1 x automotive relay (per selected pin count and coil voltage)
Relay socket and pigtail not included — use any standard ISO 280 relay socket or solder directly to the spade terminals.
Compatibility & Applications
This relay fits any wiring harness or socket designed for the ISO 280 automotive relay footprint. Typical applications include:
- Aftermarket fog light and driving lamp installations
- Headlight upgrade circuits (HID/LED conversion harnesses)
- Auxiliary cooling fan controllers
- Fuel pump priming circuits and fuel pump speed control
- Air conditioning compressor clutch engagement
- Battery isolators and dual-battery automotive setups
- Caravan, RV, and boat 12 V/24 V accessory wiring
Not suitable for: AC mains switching (this is a DC relay), continuous loads above 40 A (use a 60 A or 80 A relay), inverted polarity systems where the chassis is positive, or applications requiring contact bounce protection (add an external snubber).
Why Trust Us
Operated for 5+ years across 35+ countries by a UK-incorporated company specializing in renewable energy and small-electronics components. Every order ships with tracked delivery, a 30-day return window, and a manufacturer-backed warranty against defects. Technical questions are answered by email at info@54energy.net. Last updated: May 2026.
Frequently Asked Questions
Should I buy the 4-pin or 5-pin variant?
4-pin (SPST normally open) is the right choice for simple on/off circuits where you just need to switch a single load on when the coil is energized — fog lights, horns, fan controllers. 5-pin (SPDT changeover) is what you need when you also want a normally-closed contact that breaks when the relay activates — useful for headlight high/low changeover, or for monitoring circuits that need to know when the relay is engaged.
Why match the coil voltage to my vehicle?
The coil is the electromagnet that pulls the contacts closed when energized. A 12 V coil pulls in at roughly 8–10 V and drops out around 4–6 V; a 24 V coil pulls in at 16–20 V and drops out around 8–12 V. Powering a 24 V coil from a 12 V battery will not pull the contacts in; powering a 12 V coil from 24 V will burn it out within minutes. Match the variant to your vehicle's electrical system.
Do I need a flyback diode?
For relays driven by ECU outputs or sensitive solid-state switches, yes — add a 1N4007 or similar diode in reverse-bias parallel across the coil to clamp the back-EMF spike when the coil de-energizes. For relays driven directly from a mechanical switch, the diode is optional. This product does not include an internal flyback diode.
How fast does shipping take?
Orders are dispatched from regional fulfillment partners in North America, Europe, and Asia. Typical delivery is 5 to 15 business days depending on destination country, with tracked shipping included. Specific timelines per destination are listed in the Shipping Policy.
How does this automotive relay compare to others in its category?
Within the automotive relay category, the meaningful comparison points are contact rating, contact material, coil voltage options, and pin configuration availability. This product uses 40 A silver alloy contacts, both 12 V and 24 V coil variants, and both 4-pin and 5-pin pin configurations — the configuration that fits the broadest set of automotive accessory and aftermarket installations and drives the lowest return rate within our automotive-components category.
Can I request a quote or estimate?
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