Just replace the coolant and forget about the meter. Coolant should be pink. If it's another color then who knows what the other owner dumped into it.

 

Just replace the coolant and forget about the meter.

Don't knock it just 'cause you don't understand it.
This is a valid test that provides useful information, not a replacement for the service schedule.
It's no different than adding a restriction gauge to monitor the air filter performance.

 

http://www.toyotanation.com/forum/1...official-ultimate-2003-2008-corolla-matrix-pontiac-vibe-maintenance-thread.html

 

Greenpus is absolutely right. And it is what the dealer would do too. Unless recently replaced, which you probably don't know, the coolant is due to be replaced anyway.

No one normally performs tests on coolant. Replacing it at the prescribed interval is sufficient.

 

The reading from coolant to ground (battery -) is the valid one. Forget the reading bat+ to coolant.
Did you use a piece of bare copper wire to dip in the coolant? The white metal (likely chrome) plating of the meter probe can shift the reading.
Under 0.3VDC is considered OK.

 

No, did not use bare wire but I certainly can when I feel I need a more accurate reading. For now I'd be satisfied to understand the NEGATIVE reading. When I first read my meter and saw the mid .2 volt range I was satisfied it was within limits, until I noticed it was in the negative. I can find nothing on this.
Approaching 90,000 miles I will go ahead and flush, and will become intimately familiar with the maintenance thread sticky. Thank you for the referral.
So anyone else understand the voltage test and how it relates to the ionization of the different metals have any ideas about my negative voltage?
CircuitSmith, did you notice I said negative voltage? Is this okay, or maybe something going on chemically that I should address?

 

So anyone else understand the voltage test and how it relates to the ionization of the different metals have any ideas about my negative voltage?
CircuitSmith, did you notice I said negative voltage? Is this okay, or maybe something going on chemically that I should address?

Two dissimilar metals immersed in a electrically conductive liquid can form a crude battery.
The metal parts of the car that touch the coolant form one side and the probe you insert is the other.
The voltage of that battery is partly determined by the difference in the metal elements electronegativity.
Electronegativity correlates with a metals' resistance to corrosion.
Gold's is 2.5.
Using a probe of unknown material could shift your reading enough to swing it the other way.

The electronegativity of copper is 1.9.
Most meter probes are clad with nickle or chromium, or some "white metal" alloy.
Nickles' electronegativity is really close to coppers', but chrome is 1.66 and would throw your reading off by 0.24V.

Aluminum is a dominant part of modern cooling systems and its electronegativity is 1.6.
Difference between copper and aluminum is 0.3V.

 

Just switch the leads around to get a positive reading.

 

At normal operating temperature at idle and at about 2000 rpm, I read about negative .23 vdc. That's with the positive probe in the coolant and negative probe on ground. Switching to positive probe on positive battery terminal, and negative probe in the coolant, I read full battery voltage.

:surprise: Why are you touching the battery's positive and negative terminals at all?! :surprise:

To test the antifreeze, set the meter scale to 20 DC volts, then with the engine off, place the positive (+) lead of your meter into the antifreeze (not touching any part of the radiator, just the fluid), and the negative (-) lead of your meter on a good ground, like the engine.

A voltage reading of 0.2 volts is OK. A reading around 0.5 volts should be considered marginal. Anything above 0.7 volts - your coolant needs to be flushed and replaced.

Repeat the test with the engine idling to test your grounds. If you show MORE voltage than when the motor was off, then you have a system leaking electricity into the coolant.

If so, run the engine with all accessories on and watch the voltmeter as an assistant turns off the accessories one at a time. When the voltage drops below 0.01V (assuming good antifreeze), or when it drops back to the voltage in the initial test with the motor off, you have found the circuit with a poor ground. Do the same test while cranking the starter... A poorly grounded starter can destroy the radiator and or heater core in a matter of weeks.

http://www.wmsbrg.com/cadillac/Richmond/Tech_Tips/Antifreeze is the lifeblood of your car.htm

 

Thank you highpsi. That gives me a good idea, the next time I need gas I'll just paint an "F" over the "E" on my fuel gauge. That'll work, right?

 

Thank you for your reply. It really adds a lot to the site. I was not trying to be a smart ass about it. Your meter will read the conditions you have set up. If you reverse the conditions (swap leads) you will get the value you are looking for. From reading the info in your post you had a good value but the polarity was switched.

 

Thank you Invader. I was told to just use negative terminal for my ground, but I got the same result on an engine ground. Using the positive terminal and the negative lead in the coolant, I determined that the coolant does have continuity with ground, which logically seems inevitable, since it's contacting metal parts, but nonetheless seems like it could be harmful.
I will try the tests tomorrow eliminating different circuits, looking for a voltage change, but I still have no suggestions to what conditions could have caused my negative voltage when performing the initial, at idle, test you describe.