Testing antifreeze

In an article in the February 2020 issue there was a mention made of using a multimeter to test the condition of the antifreeze. Does it apply to the old-type antifreeze and the newer OAT antifreezes? I am just wondering if it just works the OAT only.

I must admit I had never heard of using a multimeter to test antifreeze.

Dinkar Jhalera

The method of testing the coolant using a multimeter is actually quite an old practice, and as mentioned in the answer in the February 2020 edition the testing of the coolant mixture using a digital multimeter only gives an indication of its anti-corrosive properties and not its ability to act as an antifreeze to prevent the cooling system from freezing.

As such, the test is not commonly carried out and the more accurate methods to test the freezing point of the coolant are normally used, such as a hydrometer or refractometer.

The multimeter test is actually more relevant to the older types of antifreeze and the process is used to test the electrolyte level of the coolant. Electrolysis begins to occur when two similar metals exchange electrons, which then causes corrosion in the metals. Older vehicle design also used to use a wider range of metals in the system with iron, aluminium, brass and copper often present. Modern vehicles have a more uniform approach to the metals used because the designers are aware of the effects of electrolysis.

Vehicle manufacturers now often specify that the cooling system should be filled with an antifreeze and distilled or deionised water mix to reduce the electrolyte level of the coolant.