Review on Prestone AF 1420 Antifreeze Coolant Tester by Ans Brownlee

Works great. reliable, durable, accurate. tested on new Prestone Premix (-34 F). The tester shows -34. Easy to use. easy to read. BUT. should keep the coolant in the charge line. and a vertical tester. for proper reading. Defect. #1. Air bubbles stick to the indicator. B. by ingress of coolant through the suction hose when the rubber bulb is quickly compressed due to the too large diameter of the hose. It's annoying and difficult to squeeze the tester to get rid of the bubbles. Defect. #2. Suction hose too short. . buy a 1/8" fuel hose. Cut 3 1/2" long. Insert 1/2" of this hose into the end of the tester's suction hose. Squeeze firmly. It's a tight fit. Don't worry. There's plenty Friction to keep it tight and not fall out. This fix solves the short hose problem. This fix also solves the air bubble problem. It seems that due to the much smaller inner diameter of the fuel line hose, air bubbles don't get into the suction hose.. This helps to slowly squeeze the rubber ball fully and then hold it for a second to allow the air bubbles to dissipate.. then slowly release the rubber ball.. and the coolant will be sucked into the tester easily and bubble-free. works for me. PS Me replacing two (2) of my identical 20-25 year old. old Prestone testers due to loss of calibration. They will read 10 - 12 degrees. F is lower than it should be. these. - 24 Degree F vs actual - 34 degrees. F testing a new Prestone masterbatch. Perhaps the red gauge has had oily dirt on it over the years, making it heavier and causing it to show a higher temperature. I tried cleaning with a degreaser but the result stayed the same. Maybe the Prestone people can guess. ? .