Real Time Alternator Tester, Battery Monitor, Voltage Display

Introduction: Real Time Alternator Tester, Battery Monitor, Voltage Display

About: I prefer to make my own things whenever possible.

It's very important to monitor the health of your car's charging system. Now days it's very easy, here is how.

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Step 1: Voltmeter

Buy a 0 - 30 VDC voltmeter. I bought mine at amazon for about 2.50 usd.

Step 2: Connector

I used a cork and shaved it a little so it would fit in the cigarette lighter.

Made a small channel so the positive wire would have extra room.

Added a screw at the bottom of the cork to make contact with the positive source.

Attach the positive wire to the screw. Now days, the voltmeters are protected if the polarity is reversed.

Use a smaller screw to mount the negative (black) wire to the side of the cork, this will make contact with the negative source.

Step 3: Mounting

I used double sided tape to mount the voltmeter near the power source location.

Step 4: Final Product

Finally, plug in and turn your ignition on.

So what is a healthy charging system?

Anytime the engine is running (even with all systems a/c, heater, headlights, stereo on), the meter should read 12.8 VDC or higher; otherwise, chances are your alternator is not working properly.

When the engine is off and the ignition is on the accessory position, the meter should read 12.0 - 12.8 VDC as shown in the picture.


This is not a battery tester, even though the meter may show 12 VDC does not mean the battery is good, have your battery professionally tested if necessary. Any auto parts store will test it for free.

Always read your car's manual.

This instructable is for informational purposes only. I am not a professional mechanic nor electrician.

Thanks for reading.

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    4 years ago

    Very nice. I always believe in voltage monitoring of a a car alternator. Auto makers should include it as standard in the instrument cluster.