---
product_id: 47624755
title: "EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack"
brand: "epauto"
price: "$U2059"
currency: UYU
in_stock: true
reviews_count: 8
category: "Ep Auto"
url: https://www.desertcart.uy/products/47624755-epauto-30-40-amp-relay-harness-spdt-12v-bosch-style
store_origin: UY
region: Uruguay
---

# 40A max switching current 10ms ultra-fast operate time UL Listed safety wires EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack

**Brand:** epauto
**Price:** $U2059
**Availability:** ✅ In Stock

## Summary

> ⚡ Upgrade your ride’s electrical game with EPAuto’s powerhouse relay harness!

## Quick Answers

- **What is this?** EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack by epauto
- **How much does it cost?** $U2059 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.uy](https://www.desertcart.uy/products/47624755-epauto-30-40-amp-relay-harness-spdt-12v-bosch-style)

## Best For

- epauto enthusiasts

## Why This Product

- Trusted epauto brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Built to Last 🛡️:** UL-listed wires and impact-molded sockets ensure durability and safety.
- • **Powerhouse Switching ⚡:** Handles up to 40 amps for heavy-duty automotive demands.
- • **Versatile 5-Wire Design 🔌:** Includes common, normally closed, and normally open terminals for flexible wiring.
- • **Value-Packed 4-Pack Deal 💼:** Four relays and sockets bundled for multiple projects or backups.
- • **Lightning Fast Response ⏱️:** Operates in just 10 milliseconds for instant circuit activation.

## Overview

The EPAuto 30/40 AMP Relay Harness is a UL-listed, heavy-duty automotive relay kit featuring a 40A max switching current, 5-wire Bosch-style sockets, and ultra-fast 10ms operate time. Designed for reliability and versatility, this 4-pack bundle supports high-load applications like headlights, starters, and cooling fans, making it a must-have for professional-grade vehicle electrical upgrades.

## Description

Contact Capacity: Normal switching Capacity (res.load): - NO 40A 14VDC - NC 30A 14VDC Max. switching current: 40A Max. switching voltage: 30VDC Max. switching power: 560W Characteristic Data: Initial contact resistance (at 6VDC 1A): 50mΩ Max. Operate time (at nominal volt.): 10 msec. Max. Release time (at nominal volt.): 5 msec Max. Initial insulation resistance: 100MΩ Min. (DC500V) Initial dielectric strength: - Between open contacts: AC500V, 50/60 Hz 1Min. - Between coil and contact: AC500V, 50/60 Hz 1Min. Vibration resistance: - Functional: 10 ~ 55Hz at double amplitude of 1.5 mm - Destructive: 10 ~ 55Hz at double amplitude of 1.5 mm Shock resistance: - Functional: 20G Min. - Destructive: 100G Min. Endurance (operations): - Mechanical (at 7,200 ops./h): 10,000,000 - Electrical (at 600 ops./h): 100,000 Ambient Temperature: -40°C ~ +125°C (no condensation)

Review: Work great for a variety of automotive things. - I have used these for everything from upgrading headlights to electric chokes and even as a starter relay on an 84 Chevy truck and had no issues. The relays are sealed well so you don't have to worry about water intrusion in the relay itself. The included wiring is a nice bonus, but it is NOT sealed so water can still get into the connections. Also the wires that are included maybe on the small side for any sustained high current, certainly not suited for a continuous 30 or more amp load. Luckily the terminals are easy to remove from the connector so heavier wire can be installed and still look professional. The mounting bracket is a bit flimsy but holds the relay in place. For the price you cant hardly go wrong, certainly much cheaper than buying them at a local parts store. Update 10/5/23 Been using these for several years now and only had one failure so the relays themselves are pretty good, specially for the price. Just remember the included wires are NOT up to the task of a 30 amp load, even if the relay is. The wires are marked as 16awg which is OK for up to a 15 amp load, depending on the length of the wire used in the circuit and how much voltage drop is allowable. Have successfully used for electric radiator cooling fans after replacing some of the wires in the relay connector. Personally, I make new wires for the power supply side and the load side of the relay (terminals 30, 87 [& 87a if it is being used]) if the load is over 10 amps. Terminals 85 & 86 are fine since they are just used to activate the relay and that does not use much current at all. As always, make sure any hot wires are fused with an appropriate sized fuse for the wires and circuit load as close to the battery as possible. Relays are still 5 star, specially for the price. The wiring and connector would be more like a 2 since it is so far below the rating of the relay, but again, for the price you can't expect much. At this price point, you are lucky to get a connector at all.
Review: Never know when you'll need a couple of these.... - Purchase them in volume. Work well with add on fog or driving lights. Or performing a bypass method for high and low beam when your million dollar daylight running light module expires. Two of these and a fuse holder and a little time and your in business. Great quality and work very well.

## Features

- 40A/30A high switching capability.
- Heavy-duty impact molded relay socket with 5 WIRES。White (common), Black (normally closed), and Yellow (normally open).
- Package Include: 4 relays + 4 relay sockets with wires.
- Safety UL Listed 6" wires with pigtail leads for the main contact.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B072QXDZRD |
| Best Sellers Rank | #29,307 in Automotive ( See Top 100 in Automotive ) #13 in Automotive Replacement Starter Relays |
| Brand | EPAuto |
| Brand Name | EPAuto |
| Coil Voltage | 12 Volts (DC) |
| Connector Type | Relay Socket |
| Contact Current Rating | 40 Amps |
| Contact Material | Silver |
| Contact Type | Spdt |
| Current Rating | 40 Amps |
| Customer Reviews | 4.7 out of 5 stars 6,852 Reviews |
| Manufacturer | EPAuto |
| Maximum Switching Current | 40 Amps |
| Minimum Switching Voltage | 1 Volts (DC) |
| Mounting Type | Socket Mount |
| Operating Time | 0.01 Seconds |
| Operation Mode | Automatic |
| Specification Met | UL |
| UPC | 707129801449 |
| Upper Temperature Rating | 125 Degrees Celsius |
| Wattage | 560 watts |

## Product Details

- **Connector Type:** Relay Socket
- **Contact Material:** Silver
- **Contact Type:** Spdt
- **Current Rating:** 40 Amps
- **Mounting Type:** Socket Mount

## Images

![EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack - Image 1](https://m.media-amazon.com/images/I/61dgzu6St0L.jpg)
![EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack - Image 2](https://m.media-amazon.com/images/I/717+AKVZzHL.jpg)
![EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack - Image 3](https://m.media-amazon.com/images/I/71A038LGcgL.jpg)
![EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack - Image 4](https://m.media-amazon.com/images/I/71ml-xREnRL.jpg)
![EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack - Image 5](https://m.media-amazon.com/images/I/81dMUDdiZaL.jpg)

## Available Options

This product comes in different **Size** options.

## Questions & Answers

**Q: Where does the red wire connects to?**
A: The red wire connects to pin 87a which remains in contact with the common (pin 30, blue) when the relay isn't energized.  this is known as the "Normally closed" (NC) circuit.  Don't use it unless you want the relay to power something off when the relay activates; i.e., for most operations you leave it disconnected.

**Q: What gauge are the leads that come off the relay?**
A: The wire on these harnesses are 16AWG and are too small for powering vehicles electric fan on radiator which pulls 15-30A per fan.
Use a 30A fuse right after the battery going to the 85/86 on relay, make sure the 30 & 87 on relay have 10ga OFC primary wire.
You need 10AWG guage for 7-16ft applications, it has to be OFC/Tinned Copper, make sure it's not CCA. GS Power brand on Amazon has OFC called 100% pure copper.
Pick up yellow(12-10 guage) heatshrink butt connectors(to connect the wires properly), yellow heatshrink female spade connectors(for relay post prongs) and some yellow heatshrink ring connectors in multipack of different ring diameters(for grounding the wire to Frame bolts)
Then get heatshrink tubing 1/4" should be fine if it's 3:1 or 4:1 Wirefy is a good brand. I get the spools instead of the precut packs.
Heatshrink connectors and durable heatshrink tubing is extreamly important for automotive purpose, the weather in vehicles can corrode it and cause melting or worse.

**Q: Will these work to shut off compressors for air ride suspension on a truck**
A: As long as the total amperage draw of the compressor and any other power consuming components of the air suspension system are less then the 40 amp relay, these should work fine.

**Q: Im more of an ac instead of dc guy but u can run 24v through ur no terminal just has to have 12v to bring in the coil on the relay correct?**
A: You can apply 12VDC to the coil (usually, that means 10 -15VDC) to close the contacts of the Normally Open terminals.  When the Normally Open terminals are closed, the Normally Closed terminals are open.Once the terminals are closed, they can handle 30 amps DC.There isn't a specification for the voltage that the N/O and N/C terminals can handle... but I'm certain that they can handle 24 volts.Just don't put more than 14.4VDC across the coil.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Work great for a variety of automotive things.
*by J***S on July 5, 2019*

I have used these for everything from upgrading headlights to electric chokes and even as a starter relay on an 84 Chevy truck and had no issues. The relays are sealed well so you don't have to worry about water intrusion in the relay itself. The included wiring is a nice bonus, but it is NOT sealed so water can still get into the connections. Also the wires that are included maybe on the small side for any sustained high current, certainly not suited for a continuous 30 or more amp load. Luckily the terminals are easy to remove from the connector so heavier wire can be installed and still look professional. The mounting bracket is a bit flimsy but holds the relay in place. For the price you cant hardly go wrong, certainly much cheaper than buying them at a local parts store. Update 10/5/23 Been using these for several years now and only had one failure so the relays themselves are pretty good, specially for the price. Just remember the included wires are NOT up to the task of a 30 amp load, even if the relay is. The wires are marked as 16awg which is OK for up to a 15 amp load, depending on the length of the wire used in the circuit and how much voltage drop is allowable. Have successfully used for electric radiator cooling fans after replacing some of the wires in the relay connector. Personally, I make new wires for the power supply side and the load side of the relay (terminals 30, 87 [& 87a if it is being used]) if the load is over 10 amps. Terminals 85 & 86 are fine since they are just used to activate the relay and that does not use much current at all. As always, make sure any hot wires are fused with an appropriate sized fuse for the wires and circuit load as close to the battery as possible. Relays are still 5 star, specially for the price. The wiring and connector would be more like a 2 since it is so far below the rating of the relay, but again, for the price you can't expect much. At this price point, you are lucky to get a connector at all.

### ⭐⭐⭐⭐⭐ Never know when you'll need a couple of these....
*by P***D on February 18, 2025*

Purchase them in volume. Work well with add on fog or driving lights. Or performing a bypass method for high and low beam when your million dollar daylight running light module expires. Two of these and a fuse holder and a little time and your in business. Great quality and work very well.

### ⭐⭐⭐⭐⭐ Nice to have around for non-critical applications
*by Z***L on May 13, 2024*

I bought this set of relays so I could use one to run an electric fuel pump on my lawn tractor. The factory diaphragm fuel pump is tired and I didn't want to mess with it, so I bodged an electric pump with a relay to turn it on. I selected these because they came with the harness pigtail, they were relatively inexpensive, and the reviews were good. Those are my criteria when I buy non-critical parts to keep around. I don't want to spend the money on name-brand relays for non-critical applications such as this because an inexpensive relay will do the job just fine, and even if it doesn't, my lawn tractor is never more than 200 feet from my house. Would I use this relay on a critical system in my car, IE fuel pump? Only if I was in a real bind, and in that case I'd throw as many spares as I could find in the glovebox. Not saying these relays won't work (the one I installed is working quite well), but I have no idea what this company's QC is like or how good they will be in the long run. I suspect that most people who buy these will use them for non-critical applications-- accessories or lights on their car, adding a circuit, etc. For this they'll probably be fine, and if they're not, they'll be easy enough to swap out for something better. As for me, I'm glad I have them for little project like my lawn tractor. If I manage to use them all, I'll buy more.

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*Product available on Desertcart Uruguay*
*Store origin: UY*
*Last updated: 2026-03-09*