Testing coolant with voltmeter
 

Goofing around in the garage I put the negative lead of a multimeter in the coolant, the positive clipped to a ground. Set the meter to the 20 volt range. It started with a reading of around 0.64 volts and as I watched it slowly ticked down to zero then ticked up in the negative range.

I disconnected the battery but got exactly the same results.

I tried it with some of my other cars and got rock solid voltage readings, no ticking down.

I plan to change coolant soon, but curious why it ticks down?

Anyone else use a voltmeter to check coolant? What were your results? Is this a meaningful test of anything or just internet lore?

No..... LOL

Distilled water will not conduct electricity. However, once you start adding stuff to it like glycol and all the other things that make antifreeze, yeah, it will conduct just like most of the other water that covers most of the planet. I've never heard of using a voltmeter to check antifreeze. Only Specific Gravity..

Well, here's some educational links fro using a multi-meter to test coolant:

http://www.intermotive.net/Tech%20Tip/Tech%20Tip%20-%20June.pdf

Testing For Electrolysis

Antifreeze is the lifeblood of your car's cooling system

Cooling System Electrolysis

Coolant Check | MotorWeek

Sorry for some many links but I wanted to show that it is well founded.