If you’re like me, you’ve probably encountered your fair share of electrical gremlins while working on your classic cars. Today, we’re going to amp up our skills and dive into some crucial electrical tests that’ll help you diagnose those pesky problems. Grab your multimeter, and let’s get started!
Here’s links to things I mentioned in the video! Digital Multimeter: https://amzn.to/3DRkGa0 Test Leads: https://amzn.to/3DWv8gt Electrical Diagnostic Checklist: https://snowfamilyracing.com/electrical-checklist-sign-up/
he Heart of It All: Battery Voltage Test
First things first, everything in your car’s electrical system starts and ends with the battery. Here’s how to check it:
- Set your multimeter to DC voltage (usually 20V range)
- Connect the black probe to the negative terminal, red to positive
- A healthy battery should read between 12.2V (75% charged) to 12.6V (fully charged)
Remember, this reading is your baseline for all other tests.
Is Your Alternator Pulling Its Weight?
Next up, let’s make sure your alternator is doing its job:
- Start the engine
- Test the battery voltage again
- You should see a reading between 13.5V to 14.4V
If it’s lower, your alternator might not be charging properly. Higher? It could be overcharging.
Continuity: The Unsung Hero of Electrical Tests
Continuity tests help you check for breaks in wires, blown fuses, and faulty switches. Set your multimeter to the continuity mode (usually indicated by a sound wave or beep symbol) and touch the probes to either end of what you’re testing. A beep means you’ve got a good connection!
Voltage Drop: The Silent Killer
This test helps identify excessive resistance in your circuits:
- Set your multimeter to DC voltage
- Connect the probes across the component you’re testing while the circuit is active
- A reading of 0.1V to 0.3V is normal, anything higher indicates a problem
Parasitic Draw: The Silent Battery Killer
Ever come back to a dead battery after your classic has been sitting for a while? You might be dealing with a parasitic draw. Here’s how to check:
- Set your multimeter to the 20A range
- Disconnect the negative battery cable
- Connect your multimeter in series between the cable and battery terminal
- With everything off, you should see a reading of 0.05A or less
If you’re seeing higher numbers, start pulling fuses one by one to isolate the circuit causing the drain. This test can save you from constantly jumping your battery and help preserve its life.
Wrapping Up
Remember, practice makes perfect. Don’t be afraid to get hands-on with your multimeter. Keep these tests in your back pocket, and you’ll be well on your way to becoming an electrical diagnostics pro.
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