Best Diagnostic Relays to Speed Up Your Car Repairs Fast

Seeking the best diagnostic relays to speed up your car repairs?
Discover our top 10 picks that simplify troubleshooting and save you time.

Diagnostic relays are essential tools for anyone working on car electrical systems. They help you quickly find problems and save time. With the right relay tester, you can fix issues faster and easier.

We’ve tested and compared the best diagnostic relays to make your choice simple. Whether you’re a DIY enthusiast or a pro mechanic, these tools will help you get the job done right. Discover the top picks and find the perfect one for your needs.

List of Top 10 Diagnostic Relays

Title	Best For	Price
Sound Troubleshooting Automotive Relay Tester with Relay Puller – 12V Auto Relay Diagnostic Tool, Car Relay Tester with Battery Clips, Relay Testing Kit, Electrical Systems Tool \| Patented	This tool is for car owners. It helps you test a relay. It works for beginners. You can fix your car. It is easy to use. It has a relay puller. Use it to save time. Use it to save money. It is small. It is fast. This is great for you.	View on Amazon (paid link)
Sound Troubleshooting Automotive Relay Tester – 4 & 5 Pin 12V Auto Diagnostic Tool, Small Handheld DIY Car Tester with Battery Clips, Relay Testing Kit, Electrical Systems Tool \| Patented	This tool is perfect for car owners and new drivers. It helps home mechanics and DIY fans find faults fast. It is simple and easy to use, saving you time and cash. You will love it.	View on Amazon (paid link)
ESI 193 Black 2.5″ x 5″ 12/24V Diagnostic Relay Buddy Pro Test Kit	The ESI 193 Black 2.5″ x 5″ 12/24V Diagnostic Relay Buddy Pro Test Kit is perfect for mechanics and DIY enthusiasts who need a quick and reliable way to test relays. It’s ideal for anyone working with 12V or 24V systems and wants clear, easy-to-understand results.	View on Amazon (paid link)
YUXIVCNE 9038 Fuel Pump Relay Bypass Master Kit – Pack of 6 Relay Tester Diagnostic Scan Tool Bypass Switch Kit – Replaces 9036 9037	This kit is for mechanics. Use it to test a fuel pump and fix cars fast.	View on Amazon (paid link)
RVMARINEPAT Relay Bypass Switch 9038 Relay Tester Kit Diagnostic Tester Scan Tool & Fuel Pump Relay Bypass Master Kit Replaces 9036 9037 Compatible with Domestic GM BMW Audi Chrysler 6-Pack	This relay bypass switch kit is perfect for mechanics and DIY enthusiasts who work on Audi, BMW, GM, Chrysler, and other vehicles. It’s easy to use and helps quickly diagnose electrical issues, saving time and effort.	View on Amazon (paid link)
9038A Relay Bypass Switch, Relay Tester, Bypass Switch Kit with Amp Loop, 6-Pack, Black	This kit is for car mechanics. It helps test relays and fix cars fast.	View on Amazon (paid link)
Electronic Specialties 12/24V Diagnostic Relay Buddy (ESI-192)	The Electronic Specialties 12/24V Diagnostic Relay Buddy (ESI-192) is perfect for car owners and mechanics who need a reliable tool to test relays quickly and easily. It’s simple to use and saves time when diagnosing electrical issues.	View on Amazon (paid link)
Electronic Specialties 190 Relay Buddy Automotive Relay Tester	This tool is great for auto techs and DIY car fans who want fast, clear relay checks with no stress. It helps anyone who needs a simple and sure way to spot bad relays.	View on Amazon (paid link)
Relay Circuit Diagnostic Tool 12-24	This Relay Circuit Diagnostic Tool 12-24 is perfect for technicians who need to quickly fix circuit problems. It’s easy to use and works with both 12 and 24 volt systems.	View on Amazon (paid link)
9038A Pack of 24 Relay Bypass Switch Kit and Diagnostic Scan Switch Kit with Amp Loop	This is perfect for auto techs, DIY car owners, and shop teams who need a fast, simple way to test relay circuits. It is also great for anyone who wants a clear and reliable tool for fuel pumps, fans, motors, and more.	View on Amazon (paid link)

Detailed Reviews

Discover the top 10 Diagnostic Relays handpicked for reliability and performance. Each tool is expert-reviewed and customer-approved, ensuring you get the best value. Whether you need speed, accuracy, or affordability, this guide has you covered. Find the perfect relay tester to simplify your car repairs and save time today.

1. Sound Troubleshooting Automotive Relay Tester with Relay Puller – 12V Auto Relay Diagnostic Tool, Car Relay Tester with Battery Clips, Relay Testing Kit, Electrical Systems Tool | Patented

Sound Troubleshooting Automotive Relay Tester with Relay Puller - 12V Auto Relay Diagnostic Tool, Car Relay Tester with Battery Clips, Relay Testing Kit, Electrical Systems Tool | Patented

Sound Troubleshooting Automotive Relay Tester is a must-have tool for anyone working with car electrical systems. It quickly checks if relays are working properly.

Easy to use, fast operation, and compact design make this tester ideal for on-the-go jobs. It automatically detects pin positions and relay consistency. Green light means good, red light means bad.

Versatile fitment works with most automotive relays. Not for BMW relays. Simple and effective design gives quick and accurate results.

Pros	Cons
Quickly test relays with a simple click. Green and red lights show the results. Small and light to carry in your bag. Fits most 12V cars and trucks with ease. Save time and find the problem fast.	Not for BMW relays, limiting use for some car owners. Requires 12V battery, may not work with other voltage systems. Coil resistance must be above 20 ohms, not suitable for all relays.

Perfect For:

This tool is for car owners. It helps you test a relay. It works for beginners. You can fix your car. It is easy to use. It has a relay puller. Use it to save time. Use it to save money. It is small. It is fast. This is great for you.

Ready to Purchase?

View Price on Amazon (paid link)

2. Sound Troubleshooting Automotive Relay Tester – 4 & 5 Pin 12V Auto Diagnostic Tool, Small Handheld DIY Car Tester with Battery Clips, Relay Testing Kit, Electrical Systems Tool | Patented

Sound Troubleshooting Automotive Relay Tester - 4 & 5 Pin 12V Auto Diagnostic Tool, Small Handheld DIY Car Tester with Battery Clips, Relay Testing Kit, Electrical Systems Tool | Patented

The Sound Troubleshooting Automotive Relay Tester helps you check 4 and 5 pin 12V relays fast. It is small, easy to use, and made for clear results.

Clip it to a 12V car battery and press Test. Green means good. Red means bad.

Pros	Cons
Easy relay checks with clear red and green lights. Fast test steps save time on each job. Fits 4-pin and 5-pin relays with ease. Small size makes it easy to carry and store. Works with many 12V auto relay types.	Works only with 12V batteries. Will not fit all BMW relays. Small size is easy to lose.

Perfect For:

This tool is perfect for car owners and new drivers. It helps home mechanics and DIY fans find faults fast. It is simple and easy to use, saving you time and cash. You will love it.

Ready to Purchase?

View Price on Amazon (paid link)

3. ESI 193 Black 2.5″ x 5″ 12/24V Diagnostic Relay Buddy Pro Test Kit

Test relays fast. It is easy to use.

Check 12V and 24V units. See clear lights for results. Find bad parts now.

Use five adapters inside. A strong case is included. Get quick facts today.

Pros	Cons
Tests 5 relays fast. Works with 12V and 24V. Shows good or bad clearly. Finds fault codes with ease. Includes 5 adapters and a case.	Limited to testing relays only, no other components. No built-in power source, requires external 12V/24V supply. Basic display, lacks detailed troubleshooting guidance.

Perfect For:

The ESI 193 Black 2.5″ x 5″ 12/24V Diagnostic Relay Buddy Pro Test Kit is perfect for mechanics and DIY enthusiasts who need a quick and reliable way to test relays. It’s ideal for anyone working with 12V or 24V systems and wants clear, easy-to-understand results.

Ready to Purchase?

View Price on Amazon (paid link)

4. YUXIVCNE 9038 Fuel Pump Relay Bypass Master Kit – Pack of 6 Relay Tester Diagnostic Scan Tool Bypass Switch Kit – Replaces 9036 9037

Test your fuel pump fast. This relay kit is simple.

Use the switch to start. It fits many cars. No tools are needed.

Save time and money. Buy this kit now.

Pros	Cons
Easy install, plug-and-play design for quick setup. Controls fuel pumps, windows, lights, and more with one switch. Durable build ensures long-lasting use in all conditions. Works with Audi, BMW, VW, and more popular brands.	Limited vehicle compatibility – not universal for all car models. No instructions – setup might confuse first-time users. Basic design – lacks advanced diagnostic features.

Perfect For:

This kit is for mechanics. Use it to test a fuel pump and fix cars fast.

Ready to Purchase?

View Price on Amazon (paid link)

5. RVMARINEPAT Relay Bypass Switch 9038 Relay Tester Kit Diagnostic Tester Scan Tool & Fuel Pump Relay Bypass Master Kit Replaces 9036 9037 Compatible with Domestic GM BMW Audi Chrysler 6-Pack

RVMARINEPAT Relay Bypass Switch 9038 Relay Tester Kit Diagnostic Tester Scan Tool & Fuel Pump Relay Bypass Master Kit Replaces 9036 9037 Compatible with Domestic GM BMW Audi Chrysler 6-Pack

The RVMARINEPAT Relay Bypass Switch 9038 is a powerful tool for car repairs. It works with many car brands like Audi, BMW, and GM. This kit replaces several relay models and controls parts like fuel pumps and headlights.

Save time. Find problems fast. Plug it in and test your car’s circuits easily.

Made with strong materials, this relay tester lasts long. It handles high power safely. The 6-pack gives you many options for different jobs.

Pros	Cons
Wide Compatibility for Audi, BMW, GM, and more vehicles. Quick Diagnosis saves time on electrical repairs. Durable Build ensures long-lasting, reliable performance. Complete 6-Pack for versatile repair needs.	No instructions included, might confuse first-time users. Limited to 12V systems, not suitable for all vehicles. Bulkier size may not fit in compact toolboxes.

Perfect For:

This relay bypass switch kit is perfect for mechanics and DIY enthusiasts who work on Audi, BMW, GM, Chrysler, and other vehicles. It’s easy to use and helps quickly diagnose electrical issues, saving time and effort.

Ready to Purchase?

View Price on Amazon (paid link)

6. 9038A Relay Bypass Switch, Relay Tester, Bypass Switch Kit with Amp Loop, 6-Pack, Black

The 9038A Relay Bypass Switch is a powerful tool for fuel injection testing. It lets you control the fuel pump without using the “key on/off” system. This simplifies testing and saves time.

With its amplification loop, you can monitor current using a clip-on probe or oscilloscope. It’s easy to install, fitting vertically or horizontally in your setup.

This kit works with most automotive devices, like fuel pumps, cooling fans, and window motors. It handles up to 20 amps continuous and 30 amps surge, making it reliable for 12V systems.

Pros	Cons
Test fuel pumps without using the ignition key. Easy installation with a simple plug and play design. Monitor current easily using the built-in amp loop. Fits most cars and works for many different devices. High power range handles up to 30 amp surges.	No automatic shutdown feature for safety. Limited to 12V systems, not for higher voltages. Manual control, no remote operation option.

Perfect For:

This kit is for car mechanics. It helps test relays and fix cars fast.

Ready to Purchase?

View Price on Amazon (paid link)

7. Electronic Specialties 12/24V Diagnostic Relay Buddy (ESI-192)

The ESI-192 Diagnostic Relay Buddy gives fast, clear relay checks. It works with 12V and 24V systems with ease.

It tests relays in seconds. It helps you spot faults fast. It keeps your work simple.

It is light and easy to hold. It has a strong black body. It is built for daily use.

Pros	Cons
Quickly test 12/24V relays with ease and accuracy. Compact design fits in any toolbox for on-the-go repairs. Saves time diagnosing electrical issues efficiently. Durable build ensures long-lasting performance.	No battery included, so you’ll need to buy one separately. Limited compatibility with certain vehicle models or systems. Basic design lacks advanced features for professional use.

Perfect For:

The Electronic Specialties 12/24V Diagnostic Relay Buddy (ESI-192) is perfect for car owners and mechanics who need a reliable tool to test relays quickly and easily. It’s simple to use and saves time when diagnosing electrical issues.

Ready to Purchase?

View Price on Amazon (paid link)

8. Electronic Specialties 190 Relay Buddy Automotive Relay Tester

The 190 Relay Buddy runs fast. It tests coil and switch contacts. It uses 12 V battery.

This tool auto‑checks with a good/bad light. It detects bad relays quickly. It works on 4‑pin and 5‑pin models.

The display is clear. The unit is small.

Pros	Cons
Fast test finds bad relays quick Easy auto check shows good or bad Fits 4 and 5 pin relays Loads contacts to spot high resistance Runs on a simple 12V source	Limited to 12V systems, not for other voltages. No advanced diagnostics, only basic good/bad indication. Requires vehicle battery, not standalone power source.

Perfect For:

This tool is great for auto techs and DIY car fans who want fast, clear relay checks with no stress. It helps anyone who needs a simple and sure way to spot bad relays.

Ready to Purchase?

View Price on Amazon (paid link)

9. Relay Circuit Diagnostic Tool 12-24

The Relay Circuit Diagnostic Tool 12-24 helps you find faults fast. It checks a wire, part, or relay with one push. It is simple and quick to use.

It has easy ports for other diagnostic tools. It can also jump the relay for remote start work.

Use it on 12 volt and 24 volt systems. The kit includes the tester, 6 relay leads, and 1 universal lead. It is a smart tool for fast circuit checks.

Pros	Cons
Instantly find bad wires or parts without a meter. Works with both 12 and 24 volt systems. Remote start your engine for easy work. It has extra ports to link with more tools. Get a full kit with leads for many jobs.	Limited to relay and wire issues, not a full diagnostic tool. No multi-meter functionality, extra tools still needed. Basic kit, may need extra leads for some relays.

Perfect For:

This Relay Circuit Diagnostic Tool 12-24 is perfect for technicians who need to quickly fix circuit problems. It’s easy to use and works with both 12 and 24 volt systems.

Ready to Purchase?

View Price on Amazon (paid link)

10. 9038A Pack of 24 Relay Bypass Switch Kit and Diagnostic Scan Switch Kit with Amp Loop

This relay kit is great. It helps you test circuits fast. Use it to save time now.

The diagnostic switch is simple. It fits many car models.

Check current with the loop. It is a strong tool.

Pros	Cons
Fits many car relay systems. Works with 9036A and 9037A. Tests pumps, fans, and motors fast. Handles high power with ease. Installs in seconds, no fuss.	May not fit all relay layouts Needs care when used by new techs Short leads can limit reach

Perfect For:

This is perfect for auto techs, DIY car owners, and shop teams who need a fast, simple way to test relay circuits. It is also great for anyone who wants a clear and reliable tool for fuel pumps, fans, motors, and more.

Ready to Purchase?

View Price on Amazon (paid link)

Buying Guide

Diagnostic relays are must-have tools for fixing car electrical issues. They save time and make repairs easier.

Choosing the right one can feel tricky. Here’s a simple guide to help you pick the best diagnostic relay for your needs.

Compatibility:
Make sure the tester works with your car’s voltage (12V or 24V) and relay types. Some tools don’t fit all models, like BMW relays.
Ease of Use:
Look for a tester with clear lights (green for good, red for bad) and simple buttons. It should be easy to handle, even for beginners.
Portability:
A compact and lightweight design is great for on-the-go jobs. It should fit easily in your toolbox or glove compartment.
Versatility:
Choose a tester that works with 4-pin and 5-pin relays or comes with adapters for different types. This makes it useful for more tasks.
Durability:
Go for a tester made with strong materials that can handle daily use. It should last long and work reliably.
Extra Features:
Some tools have bypass switches or current monitoring. These features can make testing faster and more detailed.
Price:
Pick a tester that fits your budget but doesn’t skimp on quality. A good tool is an investment that saves time and money.

With these tips, you’ll find the perfect diagnostic relay for your car repairs. Happy testing!