Pack-1 Car Brake Fluid Test Pen, Automobile Fault Diagnosis Instrument, Diagnostic Test Tool Kit with 5 LED Indicators, Universal for Most Cars, Trucks and Vans (Black)

Quality and price

The first thing to note is that this test pen is designed to work for glycol-based brake fluids: DOT-3, DOT -4, and DOT-5.1. It is not intended for the silicone-based DOT-5 fluid. I tested with new brake fluid and progressively added water, and the readings initially seemed reasonable. However, the pen would not read above 3%, even when testing 100% water. Only a direct short between the probes would illuminate all 5 LEDs. Readings remain illuminated for approximately 10 seconds before the pen automatically turns off. It could just be a calibration issue, but the results are questionable.

Not many people realize but brake fluid is hygroscopic. This means it absorbs moisture over time. As it does so the boiling point lowers and the risk of getting brake fade, where when you apply the brakes the pedal sinks - increases. Brake fluid replacement is generally advised every few years but it really depends on your local environment as to how quickly the fluid will be contaminated to the point of needing replacement.This pen removes the question as to 'how soon will I need to do this' - It detects the moisture content and displays the condition of the brake fluid just by removing the reservoir cap, turning the pen on and dipping it into the fluid.

Added the battery that doesn't come with it. Doesn't work. Verified battery was good and correctly installed. It's junk!