There’s never a good time to break down, I’m a mechanic, and very shortly, you’ll be rolling again.
A car that won’t start but instead emits a clicking sound likely suffers from a flat battery; a battery test will confirm. For now, a Jumpstart from another car will get your vehicle running again.
The possible causes include:
- Loose battery terminal
- Dirty battery terminal
- Faulty battery
- Bad starter relay
- Faulty wiring
- Bad starter
We’ll check for loose battery terminals and then check the battery itself. That said when a car makes a clicking sound like yours, the most common root cause is a flat battery. You can jump ahead to battery testing right here.
No, I just want to get rolling again – then check out the Jumpstarting procedure right here.
Batteries typically run flat for one of two reasons, a consumer was left on, or the battery is in the early stages of failing altogether. Meaning if we don’t get to the bottom of this, we’ll be here again soon.
There’s every chance you can fix this problem right now. The clicking sound is the starter motor trying to do its job, but it’s not getting enough battery power, and we have to find out why.
The reason could be as simple as a loose battery connection; a flat battery is also common. The battery may be flat because a light or some other consumer was left on. Or you could have a weak battery, meaning it’s in the early stages of failing.
No start and a clicking sound from your car are most common in the wintertime; that’s because car batteries struggle in lower temperatures.
Check The Battery Terminals
Engine vibration and rough road surfaces can cause battery terminals to come loose. An unsecured battery can put a strain on the terminals, also causing them to become loose or damaged.
To check your battery terminals, first, you’ll need to find your battery. Most cars and trucks will house the battery under the hood; other vehicles will fit them in the trunk. Some unusual places are under the passenger or driver’s seat.
If you are unsure, check your driver’s handbook or consult Google for your year make and models.
Check that both terminals, the red positive and black negative are tight and secure. Loose terminals will cause high resistance.
Dirty Battery Terminals
When checking the terminals, they should be clean and free from white crusty corrosion. If the terminals are dirty, you may well have found the problem. The build-up will cause high resistance, preventing the starter from getting power and also preventing the battery from receiving adequate charge from the alternator.
You can check for resistance between the terminal and the battery pole using a voltmeter, but you’ll need a helper to crank the engine, and this isn’t necessary at this stage unless we suspect a high resistance issue.
The corrosion is caused by battery acid; you can neutralize it by pouring a solution of baking soda mixed with water over the affected area. The acid can cause skin and eye irritation, so eye and hand protection is needed.
Rinse the terminals and remove them; they must be cleaned with sandpaper or a battery post cleaner.
Disconnecting the battery on most vehicles won’t cause any issues other than losing radio and time settings.
However, disconnecting on some higher-end and modern vehicles can cause other features, such as the electric windows, to lose their calibration and other learned transmission and engine calibrations. You can check your handbook for the correct battery replacement procedure.
Or you can avoid calibration issues by using a battery maintainer or KAM (Keep Alive Memory), which keeps power in the system even when the battery is disconnected. You can check out the KAM I use here on the tools page.
How Do I Test The Battery?
Having checked that the battery terminals are clean and tight, now it’s time to check the battery’s health. The battery may be healthy, just simply flat; you already know leaving an interior light on overnight could be enough to drain the power.
To quickly check the battery state of charge, turn on the wipers and headlights; if the wipers move over and back slowly, then yes, your battery is flat.
If the wipers move at normal speed and the lights are bright, it suggests that you may have a starter or wiring fault. (more below)
Your battery could be flat because it’s faulty; using a voltmeter or a battery tester, we can test the battery output during cranking.
For this test, you’ll need a simple voltmeter, aka DVOM. Set the meter to 20 volts DC, and place the red probe on the positive of the battery post and the black probe on the negative post. The following readings show the state of charge:
12.7 – 13.2 volts is 100% charged
12.4 volts is 75% charged
12.2 volts is 50% charged
12.0 volts is 25% charged
0 – 11.9 volts is Discharged (Flat)
If you have a 75-100% charge, move your leads from the battery posts to the battery terminals (connections); if the volt reading drops, it suggests a bad terminal connection.
Any reading above 12.4 volts means your battery should have enough power to start the engine, but there’s one more battery test we need to do before we call it good.
Your battery may read 12.65 v fully charged, but it could still be faulty; the best way to check it is to load the battery. The battery should be reading 12.4v minimum before running this test.
With the voltmeter connected, have a helper turn the key to the start position and check the voltage. A healthy battery won’t drop below 9 volts when fully loaded.
Flat Or Faulty Battery
Even with a faulty battery, the quickest way to get rolling is to boost start (jump-start) from another vehicle.
This will get you rolling, but as the battery is faulty, it may not restart after you shut it off. It could also struggle to stay running, especially at night when battery power is in greater demand.
Car batteries come in lots of shapes, sizes, and output ratings. Your car battery will be graded in cold cranking amps (CCA) and marked on the casing. The higher the CCA number, the better your battery performs in cold weather.
If your vehicle has a battery that’s too small for the engine size, it will struggle in the winter months and can cause premature battery failure.
Your battery size needs to be matched to your engine size; the CCA, casing size, and battery post orientation will be different for lots of vehicles. Your local parts store will guide you.
Your battery may be good, just flat. A faulty alternator may be the root cause of your problem. If so, a jump-start will get the engine running, but as the alternator isn’t outputting any voltage, the engine won’t stay running.
You can check your alternator using a simple voltmeter.
Leaving a light on is an obvious root cause of a flat battery, but for some, power consumers won’t be that obvious. A constant battery draw even after the engine shuts down is a real pain to fault find, especially if it’s intermittent.
A parasitic draw will flatten a battery in hours or days depending on the amp draw, battery state of health, and how often the vehicle is started.
If your battery tests ok and the battery keeps running flat, come back to this section and run the parasitic draw test.
Finding Parasitic Amp Draw
Testing for a draw isn’t difficult, just a little tedious. Removing the ground wire from the battery and wiring a DVOM (set to the amp at max) in series will allow you to read the amp draw.
Removing the fuses one at a time until the draw drops helps identify the affected circuit. Now the circuit must be examined for the fault; the most likely fault is the consumer itself. (electric motor, etc.)
Modern cars can’t be tested in this way as their electronics are a ton more sensitive and don’t like being disconnected from a power supply. Disconnecting power can cause learned settings to be erased, and I wrote a post about it here “car won’t idle after battery dead battery.”
Computer-controlled cars will need to go into sleep mode; this allows the car’s controllers to go into a rest mode where they consume minimal amounts of power.
This usually takes about 30 minutes after shutdown; the car will need to be tricked into thinking the hood and door are closed by tripping the latches while open; this allows you to lock the car and still have access to the fuse box.
How Do I Boost Start My Car?
From experience, a good quality set of booster cables makes a difference. A cheap set is a real pain in the jacksie; the crocodile clamps never make good connections with the battery terminals.
You can boost start (jump-start) your car from another car or any 12-volt battery that’s strong enough. Have a neighbor park their car next to yours; the batteries should be within six feet, approx. close enough to attach your jumper cables.
Jump-starting is simple.
- Put the jumper cables on in sequences 1, 2, 3, 4. (4 is placed on any available chassis metal)
- Now start your car and leave the cables attached and your car idling for a few minutes before removing them.
- Now with the engine running, remove the jumpers in reverse order 4, 3, 2, and 1.
Failing or leaking batteries often vent flammable gases, and so we place the number 4 jump cable on the chassis metal away from the flat battery to prevent any possible accidental ignition source.
Instead of boosting, you could charge the battery. However, this may take several hours, depending on the battery’s size and the charger’s amp rating.
Using a charger is easy; the two connectors are color-coded red for positive and black for negative. If your battery is very low, the charger fail-safe system will kick in, preventing it from charging.
To override this, connect your flat battery to another charged battery as though you are jump-starting. Now connect the battery charger, and charge for an hour before removing the booster cables and continuing the charge.
The relay is an electro-mechanical device used to control power in a circuit. It consists of a pair of contact points that, when commanded, are closed, causing power to flow (Completes a circuit).
As the relay has a moving part, the armature they are prone to wear. The contact points also suffer from arcing, which results in pitting. The pitting causes poor relay points contact (Resistance). This can result in a no-start or a temperamental operation.
Luckily a relay is easy to access and check. You’ll usually find it located in the engine compartment fuse box. Follow the infographic below to test.
A faulty relay will sometimes rattle when shaken, but this isn’t a definitive test. It’s better to remove the relay and test using a voltmeter and battery as per above. Want a tool to test it? Check out this neat little relay tester on the electrical tools page.
My Battery Is Good, But Still Won’t Start?
OK, so far, you’ve checked the battery terminals are tight and free from corrosion. You’ve also tested the battery, and it’s good; the relay is tip-top; now what?
At this point, we’re going to run a test called a voltage drop test. This is a really simple test that will tell us where the fault is.
As you probably know, voltage moves around in a circle (circuit); any restriction in the connections or wiring will cause less power or no power at all. Restrictions (resistance) can take the form of loose connections, broken wires, or corrosion in or on any of the components of that circuit. Some of which we’ve already checked.
The best test for a circuit is the volt drop test.
Simple Volt Drop Test
The volt drop test, as you know, measures the difference in voltage between two points. A higher reading on the meter when the circuit is under load (in our case, engine cranking), means there is resistance (Restriction to voltage flow).
We’ll need to check the power side of the circuit and the ground side. Tolerances are different for each, .2v on the ground and .3v on the positive, but older vehicles may read a little higher .5v.
For this test, you’ll need a voltmeter, and this test won’t work in a circuit that isn’t loaded; a helper will need to turn the key to the start position as you test.
Power side test
A reading around .3 volts is normal, lower is better, but a reading above .5 v on the power side of the circuit indicates a restriction in the flow of power. Check the connections. Are you sure they’re secure and clean? Check the wiring for chafing (rubbing), corrosion, and breaks.
Wiring is made up of individual strands of wire; broken strands will cause resistance to the flow of power.
The solenoid gets power directly from the battery. The solenoid control wire is powered from the starter relay, located in the engine compartment fuse box. The ECU (Engine Control Unit, aka PCM, ECM) activates the starter relay.
Ground side test
The ground side measures what’s not being used; it should be a small reading, no more than .2 of a volt; any reading above indicates a possible bad ground or a faulty starter motor.
To rule out a bad ground connection, check the battery negative to the chassis ground strap, wiggle the wire as you test, and remember to have the helper turn the key to the crank position.
A rusty or broken chassis ground or chassis-to-engine ground strap is a common fault; another quick test for this condition is to use a jumper cable to connect the negative terminal of the battery to any clean metal part of the engine block, cylinder head or transmission.
If the car now starts, you find your problem and replace your chassis grounds.
Testing The Starter Motor
The starter motor has a tough job, and it needs to be in great shape. The starter is an electric motor, and you can think of the solenoid attached to it as an on/off switch to power the starter.
As the solenoid is clicking, we know it’s getting power, but we don’t know if there’s a problem in the control circuit; it’s not common, so we’ll leave testing the control circuit until last. (see below)
You already know the solenoid is controlled by a control circuit which is activated by the ECU through the starter relay. In this next test, we’ll bypass the solenoid; the result of this test will tell us if our starter is good or bad.
IMPORTANT Before attempting the above test, put the parking brake on, and if your car is manual, make sure it’s in neutral. A manual transmission car could jump forward if in gear.
If you can gain access, some cars will be difficult; use a jumper wire to test the starter solenoid (blue wire in the picture above). If the starter turns as normal, you found your fault, a bad starter solenoid.
Replacing just the solenoid will be less expensive but may not be available for all models; a complete starter motor may be your only option.
A control circuit wiring fault is also possible but is much less likely; I have included a control circuit test below.
Starter Control Circuit
A basic starter motor control circuit will consist of a battery, ignition switch, relay, and fuse.
Modern vehicles will likely have PRNDL or clutch pedal lockout switch, and the ignition won’t control the solenoid circuit relay directly. It’s simply sending a signal to the engine control unit (ECU), and it sends a ground and power supply to activate the starter relay.
I made that sound complicated; it really isn’t; check out the diagrams below.
Starter Solenoid Control Circuit Testing
As previously said, we know there’s power going to the solenoid, as it’s clicking when you hit the key. But we don’t know if there’s an issue with resistance in the control circuit.
This is less likely, and that’s why this test is last. In this test, we’ll volt drop test the control circuit.
If you find a circuit with high resistance, move one test lead back to the next connection point and check again, this will pinpoint the fault.
Is the battery dead if lights work? If your headlights work and are bright, then your battery is in good shape. If the interior light stays bright when you turn the key to crank, your starter motor isn’t getting power.
Rapid clicking when trying to start the car? This is a sign of a flat battery; jump-starting is the fastest way to start the car. The battery may be flat because it’s faulty or simply run down by a light left on. Charging your battery is an alternative to jump-starting.
About the Author
John Cunningham is a Red Seal Qualified automotive technician with over twenty-five years of experience in the field. When he’s not writing about car repair, you’ll find him in his happy place – restoring classic cars.
- About the Author
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.