RT100 Ultimate Smart Relay Tester RT100 Ultimate Smart Relay TesterRelay Tester

I really like this really tester. Portable very convenient. Dual power 3 X AA battery or USB C. Very simple and easy to testing the relay. I give 4 stars because this tester not a budget choice, no build in rechargeable battery and no carrying case.like:1. fully automatic testing2. portable convenient carry3. dual power operation 3 AA battery or USB C4. details user manual don't like:1. not a cost saver, no build in rechargeable battery 2. no carry case for storage 3. not a budget choice(most of similar function relay testers selling at around $25)

It's an easy tool to tell your relay working or not.

A relay tester is a really handy piece of kit to have when diagnosing automotive issues. I had intended to use this to test my windshield wiper relay, but after removing it, I discovered it was a 7 pin relay, and not a 5 pin relay. Looks like I'm going to have to test it the old fashioned way with a 12V battery and a multimeter, and another pair of hands or 2 along with some additional wiring for sending the control signals to the right pin.I had chosen this one particularly because it could be powered by 3 x AA batteries or a USB-C power source (e.g. a power bank) instead of needing to wire it to the car's battery.The method of operation is simple, put your relay in, set the number of pin on the selector switch and then press the test button. If it's good, it'll run a bunch of tests and you'll hear a whole bunch of clicks and then the indicator light will be green. If something goes wrong, it'll be red and the buzzer will sound. Quite simple, and it makes testing relays so much easier. Long press the power button to turn the unit on and off. Make sure the unit is off before removing the relay. There is an auto-off feature as well, and after 1 minute if nothing is done, it'll automatically turn off.There are 2 things I didn't like about this device which would make this product better:- The LED is extremely bright. I just need an indicator light, not a flashlight! It's annoyingly bright when using it since it's on the moment you turn it on.- The single indicator light is used for both telling you the results of the test as well as being used for a low battery power indicator. A 2nd LED for low power/battery would've been better.

This OBDResource 12–24V Relay Tester turned out to be one of those tools that immediately earns a spot in the “why didn’t I buy this sooner” category.What really impressed me right away is the power design. Being able to run it on three AA batteries or through USB‑C makes it incredibly convenient, especially if you’re working away from the vehicle or don’t want to drag a power source around. And the fact that you don’t clamp it to a car battery - not even as an option - is honestly a huge plus. No bulky alligator clips, no awkward cable management, no worrying about where to hook things up. It keeps the whole setup clean, portable, and frustration‑free.I did notice it’s a bit picky about power blocks. It doesn’t seem to like USB‑C power bricks, but it works perfectly with USB‑A blocks using a USB‑A to USB‑C cable. Once powered, though, the tester is rock‑solid. It’s straightforward, intuitive, and doesn’t bury you in unnecessary features. You plug in the relay, hit the test, and get clear, immediate feedback. It handles 4‑pin and 5‑pin relays across multiple foot positions without hesitation.What I appreciate most is that it feels like a tool designed by someone who actually uses tools. It’s compact, easy to read, and avoids the overcomplicated “gadget for the sake of being a gadget” trap. If you’re diagnosing electrical issues, verifying relay function, or just want a reliable way to rule out a bad relay quickly, this tester makes the job painless.Simple, effective, and thoughtfully designed - exactly what a diagnostic tool should be

The tester feels better built than I expected for the price. The clips are solid, the relay sockets fit well, and the controls are easy to understand. I tested a few known good relays and one old bad relay and it identified them correctly. I would have liked a slightly longer cable, but overall it works very well.

I’m not a professional mechanic, but I do most of the maintenance on my own vehicles. This relay tester is very straightforward and doesn’t require much experience to use. I tested several relays from my truck and the results were easy to understand. It’s one of those tools you may not use every day, but when you need it, it can save a lot of frustration.

I was chasing an electrical problem and wasn’t sure if the relay was actually bad. The RT100 made it really easy to check the relay before replacing anything. Setup was simple and I had a result in just a few seconds. Much faster than pulling out a multimeter and testing everything manually. Very useful tool to have around the garage.

I bought the OBDResource RT100 to help diagnose a few electrical issues on my truck, and it has been very useful. The tester is simple to operate and gives a clear result quickly, which saves a lot of time compared with checking relays manually.

I especially like that it can test different automotive relays without a complicated setup. The build quality feels solid, the clips and sockets are easy to use, and the result is easy to understand.

This is a very handy tool for DIY mechanics, technicians, or anyone who works on automotive electrical systems. Definitely worth keeping in the toolbox.

Really great product to test different kinds of relays, it saved me lots time to guess the issues. Highly recommend!

Works really well

Stumbled upon this relay tester while looking for something to simplify my troubleshooting tasks. The automatic identification feature is a game changer. Just pop in the relay, hit a button, and within seconds you get a clear readout. No more guesswork. Plus, it works on both 12V and 24V systems, which is a huge bonus for my varied projects. The audio/visual alerts are super helpful, especially when you’re working in less-than-ideal lighting conditions.It's light and portable, which makes it ideal for onsite repairs. Just a heads up, it doesn’t come with batteries, so stock up on those AA batteries or bring a power bank along. Only minor gripe is that it doesn't have a more comprehensive manual mode, but honestly, the automated feature is so handy I barely find myself needing it. For the price, it's a fantastic tool for both DIY mechanics and professionals.Way better than just swapping relays around to narrow down the problem.

I’ve been using this relay tester in my garage and it’s honestly made troubleshooting way easier.You just plug the relay in, press the button, and within a few seconds it tells you if it’s good or bad. It automatically recognizes 12V and 24V relays, including different 4-pin and 5-pin layouts, so there’s no guesswork. I like that it also has a manual mode if you want a bit more control.It’s portable too. I’ve powered it with AA batteries and also plugged it in with the included Type-C cable. Nice not having to hook it up to a vehicle battery, especially when working on the bench or doing quick roadside checks.The red and green lights plus the buzzer make it very clear what’s happening during the test. Red means faulty, green confirms status and battery level. It even shuts off automatically if you leave it sitting, which saves battery life.Overall, it’s a simple tool but super practical if you work on cars regularly. It takes the uncertainty out of relay testing and saves a lot of time.

This relay tester is straightforward and works well for quickly diagnosing automotive relays. It supports both 4-pin and 5-pin relays and can handle 12–24V circuits, making it versatile for cars, trucks, or light commercial vehicles.Using it is simple: insert the relay, select the foot position, and the tester indicates if the relay clicks and passes current. It’s compact and durable, so you can carry it in a toolbox without worrying about damage.For anyone doing electrical troubleshooting or maintenance, it saves time by verifying relay function before swapping parts. It’s not fancy, but it’s reliable and practical for DIYers and professional mechanics alike.

Easy to use