Why a Car Starter may be Drawing an Excessive Current?

Is your car turning over slowly when you start it? Or, do you hear the occasional click as you start it?

Either of these symptoms can point to a faulty starter.

Unfortunately, these signs are not limited to a faulty starter. They can as well point to other parts of the electrical system failing such as a bad battery.

One sign of a bad of failing starter is when it draws excessive current.

Such a starter depending on its sign should be replaced entirely or just the parts that are failing.

Read on to learn about how much current you can expect your car’s starter to draw and the common reasons whey your car starter may be drawing excessive currents.

Quick answer: If your car’s starter is drawing too much current, it may be the starter is faulty for example, if it has an internal short-circuit or there might be an external influence such a low battery voltage.

Yes, battery voltage affects the starter current draw. At higher voltages, the starter draws considerably lower currents than at lower voltages.

3 Reasons Why your Car Starter may be Drawing a Higher than usual Current

There are several possible causes why your car’s starter might be drawing a higher than expected current.

These are listed in order of ease of checking.

#1. Starter motor is jammed. If the starter motor is jammed, for example the pinion teeth are not locking properly, then it will draw a high current. Running motors in general draw less current that stalled motors.

This is because when running, the motor generates an electromagnetic force that counters the one causing it to rotate reducing the draw current.

#2. Starter motor shorting. If the the ignition key is held in the START position for a long time, the starter can overheat, damaging the internal insulation and creating short-circuit.

This increases the current draw by the starter.

#3. Low battery voltage. Motors draw more current at lower voltages. The current draw is determined by the formula: Power – Voltage x Current draw.

The higher the voltage, the lower the current.

How Many Amps a Car Starter Draws when Starting?

A car starter can draw anywhere from an estimated 60 amps up to 200 amps when starting the car.

This assumes starters with a power rating of about 0.8 kW to 2.2 kW.

Always consult your vehicles’ repair manual for the starter’s current draw.

How many amps a starter draws is dependent on the battery voltage and condition of the battery.

For example, a car with a 1.6kW starter with a battery voltage of 12V, draws about 133 amps. If the battery is fully charged at 13.6 V, the starter draws about 118 amps, which is 11% lower.

How to Measure a Car Starter’s Amp Draw

To test how much current the starter draws when starting, you need a voltmeter and a current meter- the clamp on type.

Steps:

Setup

  • Connect the digital voltmeter probes to the positive and negative terminals of the battery
  • Let the ground wire from the battery negative terminal run through the clamp for the current meter before connecting to the car’s ground (chassis).
  • Start the car and run it at about 200 RPMs while monitoring the current draw and the voltage.

Measurements

The current draw should be at or less than that specified in the vehicle’s owner manual.

The battery voltage measured when the car is starting should be 9.6V or higher at 68°F – 77°F.

Consult your car repair manual to confirm for your starter model.

Related Questions

Final Word

Some signs that may point to a car starter drawing too much current though not confirmatory are a car engine turning over slowly when you start it or if you hear the click as you start it.

To confirm if the starter is drawing too much power, you need to measure the current draw using a clamp-on meter and compare with the current draw specified by the vehicle manufacturer.

Possible causes of excessive current draw by the starter are jammed or stuck starter motor, low battery voltage or a shorting starter motor.

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