Car Won’t Start But the Lights Come On – A Troubleshooting Guide

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It’s early morning, and you’re rushing to get on the road and off to work. You slide the key into the ignition and twist. On comes the radio and the headlights, but other than that? Nothing.

Always at the perfect time, right?

Well, since you have landed here, I am guessing this has happened to you recently.

Trust me; I know exactly how frustrating a situation this is. But don’t worry. A few issues could mean your lights work even though the engine refuses to kick over. So, let’s run over the most common causes of when a Car Won’t Start But the Lights Come On and how to fix them.

Battery issues

If your Car Won’t Start But the Lights Come On, the most likely cause, and the place to start your troubleshooting, is the battery. Modern automobiles are heavily reliant on electrical systems and need enough voltage for the engine to start.

If your battery’s voltage drops below a certain point, the battery management software will not even attempt to engage the starter motor.

So, step one, check the voltage…

If you have a multimeter handy, grab it and have a quick look to see where the battery voltage is sitting at. To use a multimeter, just touch the positive (red) cable to the positive terminal and the negative (black) cable to the negative terminal. 12.7 to 13.2 volts is what you are looking for, with anything under 11.9 volts, meaning it’s time for a new battery.

You should also do a quick load test. To perform this test, connect the multimeter to the battery and switch the key to the crank or start position. If the voltage drops under 9 volts or does not change at all, then you have a faulty battery.

No multimeter? No worries!

To test a battery without a multimeter, just turn on the headlights and the windshield wipers to full power. If the lights are dim or the windshield wipers are running at a slower than normal speed, then you can assume that the battery is dead.

What to do if your battery is dead?

What to do if your battery is dead

First things first. Have a look at your battery. It could be a simple corrosion issue on the battery terminals, or the connections could have come loose.

If there is noticeable corrosion, get your hands on some baking soda and water and make a thick paste by mixing the two (not literally, wear gloves for this!). Disconnect the battery and remove it from the car.

Yes, that’s paramount…

Cover the terminals with the paste, and let them sit for 20 minutes. Then come back with a wire brush, wipe away the excess paste and give the terminals a good old scrub. Repeat if need be. Once you’re satisfied with the state of the terminals, reconnect the battery, and off you go!

Of course, you can also use one of these Best Battery Desulfators if you don’t want all the hassle and mess.

Still no good?

The next step is to try to jumpstart your car. For this, you will need a set of jumper cables. This Amazon Basics Jumper Cable will do just fine. You will also need a good samaritan with a car if you’re using cables. Or you can just use a handy jumpstart kit, like this Hulkman Alpha 85S I carry in my car.

If you’re using cables…

Jumper cables usually come in a pair, one black and one red. First, connect the red cables to the POSITIVE terminals, then connect the black cables to the NEGATIVE terminals on each car battery. It does not matter which car you connect to first. Once this is done, switch on the second car and let it run for 30 seconds or so, then try to turn your own car on.

If your car turns on, do not, I repeat, do not turn your car off again. Remove your jumper cables in the opposite order that you connected them, then run your car for at least 30 mins. Although if you have time, run it for an hour, then do so.

Final steps…

Once this time has passed, turn your car off, wait a minute or so, then try to turn it back on. Hopefully, your battery has recharged, meaning there is no need to replace your battery right away. If the car won’t kick over, then your car battery is kaput, and it’s time for a new one. Check out the Optima for an affordable, quality option.

Trickle charging…

The other option is to trickle charge your battery with a charger, although this can be a slow process. If you don’t have a trickle charger, then grab like this Noco Genius1.

Security issues

If your vehicle was produced over the last few decades, then it may have an inbuilt security chip in the key fob. This chip is coded to interact with the control module for the engine and will prevent your engine from turning over if it is faulty. Although, you will still be able to turn on the lights and radio.

Look at your dash…

Most cars with this security protocol will have a warning light on the dash (usually displayed as a key icon). If this warning light is showing on your dash, then you will need to head to your car manufacturer’s dealership. Your control module or key may need reprogramming.

If you have a push-button ignition on your car, try pushing it with your actual key fob. This can help the control module to read the chip inside your key fob.

Fuse Damage

Fuse Damage

If you’re unsure of where the fuse box is located inside your vehicle, grab your user manual to pinpoint where you should start. The manual will also give you all the info to find which fuse may be causing the issue.

Once you’ve found it…

Check out the fuse to make sure the internal connection hasn’t blown. Fuses are super cheap, so I always keep a few spare in my glovebox. Check out this Wowoone set for a great option if you’d like to do the same.

If one of your fuses has blown, then switch it out for a fresh one and try to start the car again. Unfortunately, replacing a fuse can often just be a temporary fix, as it may blow again straight away or soon after replacing it, indicating a deeper issue.

Another important note…

Make sure that you replace the faulty fuse with the correctly rated fuse. Different systems in cars have different power requirements. For example, internal lights only use about 1 amp while the starter motor needs closer to 200 amps.

Suppose you use a fuse with a higher amp rating than required? You could cause more damage to the system. Or, in the worst-case scenario, you could cause a fire. Plus, using a fuse that has a smaller rating than required will cause the new fuse to blow instantly.

Faulty Ignition

If all the fuses are in great shape, then the problem could be a faulty or broken ignition switch.

In a few cases, a faulty ignition switch can cause power to go to peripherals like your radio or headlights while stopping power from reaching the starter motor.

What to do now?

Fault finding with your ignition is trickier than checking your battery or fuses. But an indication this might be the issue is if you power on the car but the dash and instrument panel do not light up.

You will need to visit an auto-electrician for this fault unless you have the necessary tools and knowledge to fix it yourself.

Faulty Inertia Switch

Inertia switch? Never heard of it…

This little-known component is a safety switch that will trigger automatically in the event of a crash. It cuts the gas flow to your engine. It can also stop the flow of power to your starter motor.

The inertia switch is quite sensitive in some models of cars and can sometimes be activated by hitting a pothole. Or while driving on deep ruts and off-road. Luckily they are usually pretty easy to find and reset.

Here’s what you do…

Check the user manual to find the location for your particular model. Sometimes they are located behind the front kick panel. If the switch has been engaged, then it will usually be in the “up” position. To reset it, just flip it back to the “down” position and try to start your vehicle.

Broken starter motor

Broken starter motor

Do you hear an audible clicking noise when you try to start your car?

If so…

Faulty starter motors sometimes (but not always) make a clicking sound when they fail to start. If you hear something like this, there’s a good chance your starter is on the way out. But remember, broken starter motors can sometimes make no noise at all.

Multiple clicks…

If you hear multiple clicks, then there is a good chance the starter is not getting enough power to engage. Meaning that you most likely have a battery issue.

And a single click?

If you hear a single click, then nothing; this indicates a failing or faulty starter motor or a bad starter relay. If this single click is accompanied by a grinding or knocking sound, this is even more of an indication that this is your issue.

It is probably best to have a mechanic check it out in this case.

Top Recommendations for the Bits and Pieces You May Need

If you don’t have a multimeter, get yourself one. They’re so useful for troubleshooting these sorts of issues. I would recommend one of these Best Automotive Multimeters.

If you need a new battery, please read my in-depth reviews of the Best Car Battery, the Best Battery for Diesel Truck, the Best Car Battery for Cold Weather, or my Best RV Battery Reviews.

If you just need to recharge your battery, then depending on your model, check out the Best Deep Cycle Battery Charger, my Best Trickle Chargers Reviews, the Best Jumper Cable Reviews, the Best Car Jump Starters, the Best Heavy Duty Truck Jump Starter, and the Best 18650 Battery Charger for your money in 2021!

Ok, let’s wrap things up…

Now You Know What to Do if Your Car Won’t Start But the Lights Come On

So as we can see, there are multiple possible causes for when your lights come on, but the car won’t start. But, fingers crossed, this article has helped you at least diagnose the problem, even if you do still need to take it in to see a mechanic.

And remember, regular servicing of your vehicle is the best thing you can do to ensure your vehicle’s health and long life.

Happy driving!

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