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⚡ Diagnose Like a Pro, Anywhere, Anytime!
The TopDiag P100 Automotive Circuit Tester is a professional-grade diagnostic tool featuring a massive 40FT cable plus 20FT extension for unparalleled reach. It supports a wide voltage range (9-70V DC/AC), making it perfect for cars, trucks, trailers, and agricultural equipment. Equipped with 4 versatile modes—DC voltage, AC voltage, resistance, and tone detection—plus a built-in flashlight and overload protection, it empowers both pros and DIYers to quickly pinpoint electrical issues with confidence and safety.

























| ASIN | B07YC621J9 |
| Best Sellers Rank | #9,073 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #16 in Circuit Testers |
| Brand | TopDiag |
| Brand Name | TopDiag |
| Color | Black |
| Compatible Devices | Vehicles (12V cars, 24V trucks, trailers) and their electrical components |
| Customer Reviews | 4.6 out of 5 stars 1,930 Reviews |
| Included Components | 1*P100 |
| Item Dimensions | 6 x 2.4 x 1.2 inches |
| Item Weight | 1.9 Pounds |
| Item dimensions L x W x H | 6 x 2.4 x 1.2 inches |
| Manufacturer | Topdiag |
| Measurement Type | Ammeter, Multimeter, Ohmmeter, Voltmeter |
| Minimum Operating Voltage | 9 Volts (DC) |
| Model | P100 |
| Part Number | TopDiag |
| Power Source | Battery Powered |
| Style | P100 |
| Style Name | P100 |
| UPC | 791276754598 |
| Unit Count | 1.0 Count |
| Upper Temperature Rating | 110 Degrees Celsius |
J**Z
Great tool
Works great used a few times and has helped alot great tool to have
J**E
Great for DIY fixing vehicles
I'm more new to automotive electric so this tool definitely was perfect for me. I was able to read the instructions and diagnose my cars wiring problem in no time. The light on it is very bright so that helped me in dark cramped spaces. It functions perfect for the price.
J**L
Excellent tool
Just as good as the Power Probe that I lost.
E**I
Absolute must-have tool for DIY mechanics and troubleshooting
This 12-volt power probe is a must-have for any do-it-yourself mechanic. I’m still discovering everything it can do, but it has already become one of the most useful tools I own. It’s been especially handy at the junkyard—hook it straight to a battery and you can power electric seats, windows, and locks without tearing anything apart. Being able to test circuits directly makes diagnosing electrical issues much faster. I’ve used it to find shorts, identify broken wires, and quickly power components like locks, radios, and windows to confirm they work. It saves a ton of time compared to traditional test lights or chasing wiring blindly. The tool feels solid, works exactly as advertised, and is incredibly convenient for both troubleshooting and testing. For the price, you really can’t beat it. This is one of those tools you don’t realize you need until you have it—and then you won’t want to work without it. Highly recommended.
W**.
Great for the price.
Had issues. Seller made it right. Power probe is great. Checks ohms and send power and ground. Leads are long and work great. No problems with product after seller helped me.
E**D
Fast Diagnostic Tool
First Impression - Easy to use. The bright color is easy to find in my toolbox. This tool streamlines electrical troubleshooting on the fleet I maintain. This works on tractors, trucks, trailers and agricultural implements. Any 12-24v DC system I take it to. On mine the tip will heat up until it glows when you power something, so be careful how long you hold the power button. I use it momentarily with no problems. The beeps and buzzers are impossible to ignore because they are bright and loud. That makes this tool safer IMO. There is no internal battery, which makes it even safer, and simple to maintain. The wires are long enough to reach the tail lights on almost anything. I really like it. It's intuitive, fast, brightly colored, and makes me look like I know what I'm doing even when I really don't.
A**R
circuit tester
works good
C**C
Amazing tool for the price
First let me be clear, if you make a living using this kind of tool, get a Snap-on or Matco or something that comes with the big huge warranty and is built beefy, but for me, I only use kind of tool every so often and for that it is perfect. First, it comes with a 40 foot cable. That is amazing! I love that part and is what initially sold me on it. When doing trailer and RV wiring I can power it by the batteries in front and I have 40 feet to mess around with. I could not find another tool with this length in this price range on Amazon. This was the best. As for functions, it has all the basic functions you need and a couple of advanced ones but it is not as advanced as some of the really good automotive ones or the Flukes but again, at this price, what do you expect. That vast majority of the work you'll be doing will be done just using the normal functions so this fits the bill perfectly. Overall this is a great buy and I have used it quite a bit across hundreds and hundreds of feet of wire and I have not had an issues with it. It is accurate, and always works so I can test the circuits.
G**E
12v tester
Works well and saved me a lot oftime
J**R
Great Auto electrical testing tool
Great tool for fault finding on vehicle electrics.
I**I
good product.
good for looking shorts or relays not working.
M**R
Excelente herramienta facilita el trabajo
Muy buen producto cumple con su trabajo
G**.
Muy mala calidad
Tiene defectos de fabricación
Trustpilot
1 week ago
1 month ago