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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 | #13,347 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #20 in Circuit Testers |
| Brand Name | TopDiag |
| Color | Black |
| Customer Reviews | 4.6 4.6 out of 5 stars (1,889) |
| Included Components | 1*P100 |
| Item Dimensions | 6 x 2.4 x 1.2 inches |
| Item Weight | 1.9 Pounds |
| Manufacturer | Topdiag |
| Measurement Type | Ammeter, Multimeter, Ohmmeter, Voltmeter |
| Minimum Operating Voltage | 9 Volts (DC) |
| Model | P100 |
| Power Source | Battery Powered |
| Style Name | P100 |
| UPC | 791276754598 |
| Upper Temperature Rating | 110 Degrees Celsius |
A**R
Works great
Very easy to read and use. Great for testing circuits and loads
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.
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.
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.
A**R
Must have for mechanics
Great tester has everything I needed very high quality and a great value a must have for mechanics
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.
C**T
Power probe
Should of bought one sooner. Best tool to have for diagnosing electrical issues. Easy to use. The wire length is a little short for the grounding probe but it has not been an issue so far
J**E
It works perfectly I recommend getting one
This is a must have it will help you a lot I use it to check if solenoids are still good before going out to buy a new one
G**E
Works well and saved me a lot oftime
J**R
Great tool for fault finding on vehicle electrics.
I**I
good for looking shorts or relays not working.
M**R
Muy buen producto cumple con su trabajo
G**.
Tiene defectos de fabricación
Trustpilot
2 weeks ago
2 days ago