Electrolysis and the Fluctuating Ammeter

RedFish said

Old coolant will show more voltage than fresh coolant even in new cars that have a much different system ( more grounds routed back to the battery via a wire ).
They say one can test coolant with a volts meter. More than 4 tenths of a volt at 2000 rpm means replace the coolant. I don't know if one could get a reading that low in a classic car.

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What I have seen fairly consistent in the Automotive Repair industry trade magazine technical articles and in boxes of new heater cores is 3 tenths of a volt (300mV).

I have less than 1 tenth of a volt in my 1968 Barracuda (.086 Volt or 86mV pictured above). :dontknow:

I agree with 67Dart273 that the huge 3 volts was mostly not from electrolysis (if at all). It was from poor grounds and a faulty ignition switch.

Maybe we shouldn't be calling this a electrolysis test so much as it is a test for stray voltage in the coolant system.

Just we should periodically check for voltage with a test light or voltmeter in series with the battery ground terminal with all the electrical draw turned/taken off and ignition off.