With today’s complex cars the most important system on your car is the electrical system. Here’s an article on how to check and diagnose any problems that may exist within your charging system. When needing a tool that can test and determine electrical problems within a system such as the starting and charging system, there is no better purchase to be made.

Purchasing a Tester

For those who continually invest money in tools for their job, here’s a piece of equipment that is a must have item. There are several different types of electronic charging system testers out there, this one is from Mac tools. These testers vary in price from $199-$399. The great thing about electronic charging system testers, is the ability to test and have results within 2 minutes.

Having the correct tools for the job is the most important part of diagnosing and repairing automobiles. Testing the battery, starter, and alternator is an area where improper diagnosis can be costly. With the correct tester this job can be diagnosed within a couple of minutes. Intermediate Car Repair

Before testing the battery or any other electrical issues, making sure there is voltage present with no corrosion or poor connections is the first step into diagnosis. For more battery and electrical maintenance tips refer to the following posts:

Here is a step by step procedure on how to perform the 3 individual component tests that makeup your charging system. The tester used in this article is the Accuracy Plus tester from Mac tools.

1-The Battery Test

Hook up the battery tester color coded clamps. Red to the positive terminal of the battery and black to the negative terminal of the battery.

Hook up battery tester

Once powered up, the tester will guide you through each step of testing.

Charging system tester

The first thing the tester will ask is what the CCA or cold cranking amps are.

Battery rating

Input the amount indicated on the battery and press go. (Battery rating – 550 CCA)

Press Go

This is the amount that the tester will “load” or take away from the battery to see if it meets the rated capacity.

After pressing go, the tester will load the battery two times within 20 seconds. Then it will show “battery good” or “battery bad” on the display and the actual amount of voltage and CCA’s tested. It’s that easy.

Battery test results

Battery condition good.

Battery Results

Test results, 12.6 volts and 510 cold cranking amps.

Battery Test Results

If this battery was bad, it would show low cranking amps. 510/550 is a good test result. If the voltage tests lower than 12.0 volts, the battery should be charged and re-tested.

2-Starter Test

Immediately following the battery test, the tester will instruct you to start the vehicle.

Start the vehicle

At this point the starter current draw will automatically be tested. (The starter results will show up at the end of the last test)

Starter Test Results

Good test results should be no more than 150 amps of current draw. Any amount over 200 amps could put excess drain on the battery. This could cause problems during the winter months and may even shorted the life of the battery over time.

3-Alternator Test

This is the final of the 3 tests for the complete charging system.

With the vehicle running, you will be asked to press go and increase the throttle to 1500 RPM. During this time (approx. 15 seconds) either jump in the car and rev up the engine…

Accelerate to 1500 RPM

…or look for the throttle cable on the engine. Increase the RPM slowly until the tester tells you to maintain the RPM.

Accelerator cable

The alternator will automatically be tested by simulating the maximum amount of load devices that could be turned on from your vehicle and record the output. It will also test the internal voltage regulator functions as well.

Charging results

Here is the measurement of output from the alternator under a load test. (14.2 volts)

Alternator Test Results

Good results would be an increase in voltage by approximately 2.0 volts. (12.5 volts before starting, 14.5 volts running) The tester will show “diodes good” or “diodes bad” as a result also.

Final Results

When the test is finished, you will be instructed to turn the vehicle off. The complete evaluation of the charging system will scroll through for you to read. Here are the items tested:

  • Battery load test – with voltage and CCA results
  • Starter current draw test – with amount of amperage and voltage used
  • Alternator output test – results with load and no load voltage and amperage output
  • Alternator/Regulator – internal function test of the voltage regulator diodes

Final Thought

This tester is one of the most user friendly testers available. It’s also one of my favorite pieces of test equipment to use. If there are any electrical problems found on the vehicle being tested, the tester will tell you and stop with any further tests. This allows you to replace the faulty part and retest after the problem is fixed.