When a car starter takes over, it becomes difficult to start the engine, the battery is subjected to excessive loads and is quickly discharged. In the cold season, the situation is aggravated. The starter that takes over should be considered defective. He works hard. If the failure is not found and eliminated, the node will fail completely. Finding and repairing this malfunction is relatively easy to do on your own. What kind of breakdown is this, how it manifests itself, for what reasons, and how to fix it - is described in this material.
What does it mean - the starter takes over?
A car starter is an electric motor. Very powerful. In good condition, when starting the engine, it consumes more than 1 kW of electricity from the battery. The current flowing through the circuit at this moment is easy to calculate. To do this, you need to divide the power by the nominal voltage of the battery (12 V). Accordingly, if the starter is 1.5 kW (1500 W), then during operation it consumes a current equal to: 1500 / 12 = 125 A.
The starter battery is capable of delivering much more current. This is called the maximum cold crank current and is almost always listed on the case. For modern models with a capacity of 60 A*h or more, the norm is 500-600 A. Accordingly, if the starter, due to any defects, “requires” more current than its norm, the battery has it.
“The starter takes over” is a current consumption that significantly exceeds the calculated rate. He takes nothing but current. Much more than is necessary to successfully start the engine. This "surplus" is not used to do useful work.
What does the starter spend this energy on? Depending on the nature and cause of the malfunction, the "surplus" energy is either converted into useless heat or spent on overcoming mechanical resistance.
From personal experience, I can give 5 symptoms of a malfunction:
- The starter is not working well. Excessive current draw is not the only reason why the starter turns the engine hard and with great difficulty. Other options are described in great detail in a separate material called "10 reasons why the starter turns badly". I recommend to take a look.
- Significant voltage drop. The more current the starter draws, the lower the voltage sags. When it is working, the voltage on a well-charged battery does not drop below 11.2 V during engine start. You can check for this symptom using a conventional multimeter. Turn it on to measure DC voltage within 20 V and connect the probes to the battery terminals. At the time of starting the engine, the device will show a voltage drop. If it is noticeably lower than 11.2 V, then there is a problem.
- Starting current is too high. The more the starter takes on, the more current it consumes when starting the engine. To measure this current, you need a device called a clamp meter. A multimeter is not suitable for these purposes, since its limit is 10 A (in good models 20 A). Next, you need to find out what current is the norm for your starter. To do this, you need to know its power in watts. Divide it by 12 to get the ampere rating. If the clamp meters show significantly more, then there is a problem.
- The starter gets hot. Despite the fact that it works for a few seconds, heating can be quite noticeable. You can check this symptom tactilely.
- Characteristic smell. Any worn out electric motor emits a burnt smell familiar to many, which cannot be confused with anything. If your starter “smells” after work, then there is a problem.
Please note that the first two symptoms can also occur with a completely serviceable starter. For example, when a worn-out battery is installed on a car, which, in principle, is not capable of vigorously turning the starter. You can eliminate this possibility with the help of a load fork. Read more about this in the material "Checking the battery with a load plug".
All malfunctions due to which the starter takes over can be divided into two groups:
- Mechanical failures and wear.
- Electrical faults.
Mechanical failures and starter wear
If you look at the device of a car starter, you can see several moving elements:
- rotor or anchor;
- overrunning clutch;
- drive mechanism (retractor relay);
- planetary gearbox (not available on all starters).
First of all, check how the rotor rotates. It is mounted on plain bearings or bushings. You can determine their wear by backlash. If the rotor turns by hand with great difficulty, most likely there is corrosion or dirt inside the starter. Personally, in my practice, removing rust and dirt solves the problem in 80% of cases. In second place is the wear of bronze bushings, which are easy to replace with new ones. By the way, when there is a large play of the rotor shaft, during rotation it clings to the magnets on the housing, as a result of which the starter wedged and does not work well.
For clarity, here are a few pictures.
After replacing worn parts, cleaning, lubricating (do not overdo it) and reassembling the starter is guaranteed to work more cheerfully. But only in cases where the problem is not electrical.
Let's go back to the car starter device, the electrical part of which consists of the following key elements:
- starter power supply circuit;
- current-carrying brushes;
- rotor manifold;
- rotor windings;
- stator windings (except models with permanent magnets);
- solenoid relay windings;
- power contacts of the solenoid relay.
I will not consider the retractor relay here. This topic is described in detail in the material "How to check the starter solenoid relay". Go study.
As for the starter itself, there can be 5 problems here:
- Bad contact in the power supply circuit. This circuit begins with the terminals of the battery, and ends with the terminals on the solenoid relay. First of all, inspect all places where there may be dirt and oxides on the contacts. If there are problems with the battery terminals, additionally read the material “Battery terminals are oxidized”. It is enough to disassemble the contacts on the starter, clean and reassemble. Very often this simple manipulation is enough to fix the problem. Don't forget to check the starter power wires as well. They must be whole.
- Current-carrying brushes are worn out. To identify the problem, the brushes must be removed. On some starters this is easy to do. Other models have to be completely disassembled. The brushes must be intact, of sufficient length, without chips and traces of uneven wear. They should also spring normally, and not wedge in their guides. This is sometimes due to graphite dust and other dirt.
- Rotor collector dirty. The collector consists of copper lamellas through which the starting current is transmitted from the brushes to the rotor windings. Between them there are gaps in which there should be neither dirt nor graphite dust. If present, remove with a thin, non-metal tool such as a toothpick. Additionally, it is worth cleaning the surface of the lamellas from oxides and graphite. But not sandpaper. Use alcohol or other solvent, but not very aggressive.
- Short circuit in windings. There are several identical windings in the rotor and stator (except for models with permanent magnets) of the starter. If any of them has an interturn circuit, the winding will have less resistance than the rest. You can check this with a multimeter.
- Winding break. When one of the windings burns out in the electric motor, it continues to work, but consumes significantly more current. The starter takes over. You can find the problem winding with a multimeter.
For clarity, here are a few pictures.
When the starter takes over, it means that it is "pulling" more energy from the battery than is needed to successfully start the engine. Excess energy is wasted on heating parts or overcoming mechanical resistance. The symptoms are simple: the starter works with great difficulty, heats up, smells, consumes a lot of current and greatly sags the on-board voltage. The reasons are mechanical and electrical. Repair is reduced to the replacement of defective parts, cleaning and lubrication of rubbing elements.
For more information, see the article "Starter clicks, but does not turn the engine."