Flickering dash lights and Car Won’t Start? Here’s Why

When you see flickering dash lights your car won’t start, think dead battery

Few things are more frustrating than getting into your car, turning the key, and seeing your dash lights flicker and your car won’t start. That’s a telltale sign of a dead battery problem or corroded battery terminals that need immediate attention.

All your dash warning lights light up and flash rapidly. That’s a dead battery or bad battery connection.

Some people think that the dash lights illuminating means the battery is ok. Not true. It takes very little power to run the dash lights compared to how much power it takes to crank your engine. In fact, most automotive computers can’t work when the voltage drops to 9.6 volts or less. That’s why your dash lights are flickering; there’s not enough voltage to keep the computers powered up. Don’t jump to the conclusion that you’ve got a major problem. Keep your cool and check your battery and battery connections.

Common Causes of Flickering Dash Lights and Your Car Won’t Start

• Dead or Dying Battery— The most common reason for flickering dash lights and a car that won’t start is a dead or nearly dead battery. If the battery is weak, it might not be able to supply enough power, causing the dash lights to flicker as the electrical system struggles to distribute the remaining power.

• Corroded Battery Terminals— Corrosion on the battery terminals can impede the flow of electricity. If the terminals are corroded, the battery might still have charge, but the electrical connection could be compromised, leading to flickering lights and a failure to start.

• Loose Battery Connections— Even if the battery is fully charged, loose or disconnected battery cables can prevent the electrical system from functioning properly. This can cause flickering dash lights when the ignition is engaged, and the car won’t start.

Start by checking the battery voltage

Using a multimeter set to DC volts, touch one probe to the positive battery terminal and the other probe to the negative battery terminal. Battery state-of-charge is determined by the voltage on your meter, the type of battery in your car (standard flooded lead-acid, maintenance-free battery [no vent caps], or absorbed glass mat [AGM]}. Compare the voltage on your meter to the state-of-charge chart below. Measure battery temperature using a non-contact infra-red thermometer.

Anything less than 12.2 volts mean the battery is severely discharged

What the numbers mean

Generally, a battery voltage of at least 12.2 volts should crank your engine. However, if the voltage is less than than that, and certainly if the voltage is less than 9.6 volts, you may experience a dash light coming on, but you’ll still have a car that won’t start condition.

What’s your next step?

Corroded battery terminals can’t always be diagnosed visually. If your battery terminals don’t have good contact with the battery posts, they can’t conduct enough power to the starter.

If your dash lights flash rapidly but the car won’t start, that can be a symptom of a bad terminal-to-post condition. Another symptom is if you turn the key and hear a single click or rapid clicking.

To diagnose a bad battery/terminal connection, conduct a voltage drop test using your digital meter.

How to conduct a voltage drop test on your car battery terminals and posts

Set your digital meter to the lowest setting on DC volts. Touch one probe to the battery terminal and the other probe to the battery post. The reading you get is the voltage drop in the connection. A reading of less than 0.1 volt is considered a very good connection. The maximum voltage drop is 0.4 volts. If your reading is at or above that 0.4-volt reading, the post-to-terminal connect is not good. You should remove the terminals and clean both the terminals and posts with a wire brush. Then retest.

Test for voltage drop at the battery terminals and posts.

©, 2020 Rick Muscoplat