🧑‍🔧 How to test the starter solenoid

Checking the solenoid relay sometimes allows you to find out exactly why the starter does not work or turns badly. In most cases, this unit cannot be repaired. But rushing to change it without a full diagnosis is also not worth it. It is possible that the retractor relay is working properly, and the starter is acting up through no fault of his own. The purpose of this article is to tell in simple words about the functions, the device, the principle of operation and the main malfunctions of the node, as well as their signs and methods of verification.

Starter retractor functions

Despite its apparent simplicity, the starter solenoid relay performs far more than one function. Accordingly, when a part at least partially fails, the entire engine start system fails. The functionality of the retractor relay is partially clear from the name itself. Retractable means that it draws something somewhere. Relay - means switching (connecting) the power circuit of the vehicle's electrical equipment.

If you look at the general device of the starter, you can see what draws in the retractor relay. Its movable rod is connected through a lever to a freewheel on the starter shaft. The overrunning clutch is made in one unit with a drive gear. When the retractor retracts its rod, the overrunning clutch with the gear moves forward, due to which it engages with the engine flywheel. The assembly remains in this position until the driver releases the ignition key after a successful (or not) start of the engine.

The next function of the retractor relay is to disengage the drive gear from the flywheel when the engine is already running. This is done by the force of the spring. How the retractor retracts is discussed below. An overrunning clutch is needed in order to disengage it from the starter shaft even before the drive gear is disengaged.

Between retracting and retracting, the retracting relay performs an intermediate function. It consists in reliable fixation of the drive gear in engagement with the flywheel. If this is not done, then the gear will return to its original position before it is supposed to, and the engine will not have time to start. The holding winding of the solenoid relay, discussed below, is responsible for this function.

Well, the last two important functions of the retractor relay are switching the "plus" of the battery with the starter and reverse disconnecting the contact. Commutation occurs simultaneously with how the drive gear is engaged with the engine flywheel. As a result, the starter armature begins to rotate in a timely manner, the torque is transmitted to the crankshaft, and the engine starts. When the ignition key is released, the power “plus” of the battery is disconnected from the starter by the same retractor relay.

In total, it turns out that such a simple device as a retractor relay has 5 functions:

1. Retraction. The starter drive gear is engaged with the engine flywheel.
2. Retention. The gear is securely fixed in engagement with the flywheel.
3. Reverse move. The gear is disengaged after the engine starts.
4. Switching. The starter is supplied with starting current from the battery.
5. Shutdown. Starter power is cut off.

The retractor relay performs all these functions thanks to a simple, but at the same time ingenious device.

The device and principle of operation of the solenoid relay

Before checking the solenoid relay, it is simply necessary to at least in general terms get acquainted with its internal structure. Of course, you won’t have to disassemble it, since the node is considered non-separable. However, checking without understanding the device and the principle of operation can lead to sad consequences. Including, inept actions, you can easily burn the initially working solenoid relay.

Conventionally, its internal filling can be divided into three parts:

1. Mechanical drive. Consists of two stocks. One of them is removable (1). The second is inside (10), and is driven by windings. Spring 11 is needed in order to return the starter drive gear to its original position after starting the engine.
2. Windings. There are only two of them. Retracting (2) and holding (3). When an electric current passes through the winding, a powerful magnetic field is created in the region of the rod. When the retracting winding is working, the rod 1 moves, and the retractor retracts. When the gear is engaged with the flywheel, it is fixed due to the operation of the holding winding 3.
3. Switching node. When the retractor retracts, rod 1 pushes rod 10 through the spring, due to which contact plates 9 connect contacts 6 to each other. One of these contacts is connected to the “plus” of the battery, and the second is connected to the starter. This is how the starter is powered (“minus” comes from the ground). When the ignition switch is released, the holding winding is de-energized, the rod 10 returns under the influence of the spring 7, and the switching stops.

Additionally, it is worth considering how the switching unit of the solenoid relay and its windings work. The diagram below shows how and where the current flows. When the driver turns the ignition key, both the retracting and holding windings have time to work at the same time. However, after switching the “plus” of the battery with the starter, the retracting winding stops working, since the power “plus” is connected to the control “plus” through the relay contact. The holding winding continues to work until the driver releases the ignition key.

On a real pull-in, the connection point between the pull-in and hold windings can be seen from the outside of the device. This is a metal jumper that connects one of the power contacts to the control one. It is to this power contact that the “plus” with the battery is connected. It follows that the power contact free from the jumper goes directly to the starter. Sometimes knowledge of this feature allows you not to mix up the wires when installing and connecting the starter after checking.

That's all. This is exactly how the retractor works. Now let's look at how it refuses to work, and what signs indicate which node malfunctions.

Signs of a malfunctioning retractor relay

For clarity and ease of perception, all common (and not so) malfunctions of the retractor relay with signs and causes are collected in the table below. Directly, the method for checking the starter solenoid relay is described a little below.

We finally turn to how to check the starter solenoid relay.

Checking the solenoid relay

Let's go from simple to complex. This should always be done in order to avoid, if possible, unnecessary manipulations. Moreover, checking the retractor relay is far from a harmless procedure, and due to inexperience or negligence, you can easily make it worse than it was. Even injuries are not ruled out. Therefore, the malfunctions described in the table above will be considered from the end.

Checking the contacts of the retractor relay

Checking the solenoid relay for bad contacts is carried out even without removing the assembly from the machine. To do this, you just need to unscrew the three nuts on the back of the retractor, remove the control and power wires, look at them, clean them of oxides, dirt, rust, and so on. If everything is fine with the retractor itself, and the contacts were bad, then this may already be enough to revive or cheer up the starter. If possible, before reassembly, it is desirable to treat the cleaned contacts with a special composition to protect against corrosion.

Checking the solenoid relay for freezing

Here, too, everything is very simple, and you do not need to disassemble anything. The problem, for obvious reasons, manifests itself exclusively in winter. It is possible to understand that the retractor (or the starter itself) refuses to work due to freezing by the nature and time of the malfunction. As a rule, if moisture gets into the node, then everything continues to work normally. The solenoid relay freezes and jams usually in the morning, that is, after a long idle time of the car.

There is nothing to fix here. You just need to warm up the retractor by directing a stream of hot air at it for 5-10 minutes. This is done using a building or household hair dryer. Also, a conventional room heater with a fan helps to warm the unit. Despite the simplicity of this problem, in the future you should think about how moisture got into the starter or retractor. Perhaps the gasket has deteriorated, some bolt has loosened, or the body has been mechanically damaged. On some cars, the starter is generally located at the bottom of the engine, and water can get into it after every trip on a wet road.

Checking the solenoid relay for clogging and mechanical wear

Here you can’t do without dismantling the starter. At the same time, the starter itself does not always need to be disassembled. Often in such cases it is enough to remove only the retractor relay. Next, a rod with a spring is removed from it. Parts are inspected for contamination, corrosion or mechanical wear. Dirt and corrosion can be easily removed, but in the event of obvious wear or breakage, the solenoid relay will have to be completely replaced.

Checking the pull-in winding

This solenoid test requires only a multimeter. The assembly will have to be removed from the starter.

Diagnostics is performed in the following sequence:

1. Turn on the multimeter in dial mode.
2. Attach one probe of the device to the control contact of the solenoid relay (it is usually flat, and a thin wire fits to it when assembled).
3. Connect the second probe to the power contact with a jumper.
4. If the device squeaked or showed some meager resistance - the retracting winding is not open.
5. If the multimeter is silent or does not show anything, the retracting winding is open.

Recall that with such a malfunction, the drive gear cannot engage with the flywheel, and the switching unit does not turn on. Accordingly, the starter does not show any signs of life. There is nothing to fix in such cases. The solenoid relay with a broken winding is only for replacement.

Checking the holding winding

The purpose of this check of the solenoid relay is to determine an open in the holding winding, or to exclude such a malfunction. For diagnostics, only a multimeter is again required.

The verification algorithm is as follows:

1. Turn on the multimeter in dial mode.
2. Connect one probe to the control contact of the solenoid relay (flat thin contact).
3. Connect the second probe to the solenoid relay housing. Make good contact in this area.
4. If the multimeter squeaked or showed some resistance, the holding winding is intact.
5. If the device is silent and does not display anything on the display, the holding winding is broken.

As for checking this winding, that's not all.

Checking the pull-in and holding windings for strength

As you remember from the above, the holding winding is so called because it must hold the starter drive gear in engagement with the flywheel. In addition, at the same time, reliable contact is ensured in the switching unit. If the winding is burnt, then the magnetic field that it creates will be very weak. Accordingly, the retractor will not have enough strength to keep the mechanism in the working position for the required period of time.

The retracting winding must be worked out in such a way that the strength of the magnetic field is sufficient for the confident movement of the working rod and the introduction of the starter drive gear into engagement with the engine flywheel. If there is an interturn circuit in the winding, then it will work. But not effective enough. Finding out this very retraction force will be the second goal of this stage of checking the starter retractor relay.

To carry out the procedure described below, you will need:

1. A charged car battery (can be temporarily removed from the car).
2. Three thick wires.
3. Self-tapping screw.
4. A piece of copper wire.
5. Wooden surface.

Attention! The following steps must be carried out without delay. Before checking, repeatedly re-read the algorithm and scroll through all the steps in your head. Carefully check if you connected everything correctly, and once again scroll through the sequence of actions in your mind. If you make a mistake at this stage, yawn, hesitate, then you can injure yourself, ruin the working solenoid relay, or arrange an epic fireworks with sparks.

Algorithm:

1. Screw the self-tapping screw into the wooden base.
2. Fix the anchor (rod) of the solenoid relay to the self-tapping screw with a wire.
3. Connect the "plus" of the battery with a thick wire to the power contact of the relay without a jumper.
4. With the second wire, separately connect the "plus" of the battery to the control contact.
5. Rest the solenoid relay against the self-tapping screw so that the armature does not overcome the resistance of the spring, but enters a little inside.
6. Connect the "minus" of the battery to the power contact with a jumper.
7. If the armature is pulled inward with a slight effort - interturn short circuit in the retracting winding.
8. When the relay works, try to pull the retractor back with a moderate effort of the hand.
9. If it was not possible to pull the retractor, the holding winding is working.
10. If the armature easily left its seat and remained hanging on the self-tapping screw, the holding winding is faulty (even if there is no break, there may be an interturn circuit in it).
11. Allocate no more than 3 seconds for the entire check, then de-energize the assembled circuit by disconnecting the negative terminal.
12. If you didn’t manage to understand anything the first time, do not rush to apply power to the circuit again. Wait 10 minutes for the solenoid coils to cool down after loading.

As mentioned earlier, the retractor relay cannot be repaired. Therefore, if at one of the stages you find a break or an interturn circuit, the part is for replacement. One of the signs of an interturn short circuit of the holding winding is when the starter turns for a couple of seconds and stops itself.

Switch node test

The last step is to check the solenoid relay for malfunctions of the switching power unit. Recall that there can be either poor contact, or its absence at the right time, or even sticking. The task of the test is to determine whether the starting current goes to the starter at the moment the solenoid relay is activated.

The algorithm is this:

1. Turn on the multimeter in dial mode.
2. Connect one probe to any power contact of the solenoid relay.
3. Connect the second probe to the second of the two power contacts.
4. Fix the probes to free both hands for further manipulations (tie them with wire or clamp them with crocodiles).
5. If the multimeter has already squeaked in this position, the switching node is stuck.
6. Install the anchor (or rod) of the solenoid relay in its rightful place and drown it with force until it stops.
7. The squeak of the multimeter at this moment indicates that the switching node is working.
8. If the device is silent, the switching node is broken (there is no contact, the plates are burnt).
9. If the multimeter did not squeak, but showed a lot of resistance on the display, the contact in the switching node is too bad (soot, oxide, scale).

In fact, there is nothing to repair if something happens. The solenoid relay is a non-separable part. Nevertheless, some models, nevertheless, with the help of a hammer, screwdriver and affectionate words can be partially dismantled. If you have even hands, you can even clean the contacts, and carefully assemble everything back to its original state.

VIDEO: test starter and solenoid

Brief summary

To fully check the starter solenoid relay, it will have to be completely removed. In addition, you will need a simple multimeter, a charged battery, wires, a self-tapping screw and a clear understanding of what is happening. Without confidence in what you are doing, risking power testing a solenoid relay is highly discouraged. Limit yourself to dialing with a multimeter and simple cleaning of the node. If there is confidence, you can check the retractor relay 100%, as well as identify absolutely any of its possible breakdowns.