The term limit switch is nothing more than a common abbreviation for “limit switch”. In it, the contacts are closed without fixation by a movable rod - this is convenient for monitoring the position of moving elements. Limit switches of various types are installed in cars on the doors or in the trunk; they control the position of the brake pedal and handbrake lever.
Limit switch function
The effect of this button is that when the doors are open, a special symbol lights up on the panel. If, when setting the alarm, the door is not closed or not completely closed, that is, the limit switch is open, then the “alarm” will definitely notify you about this.
In some car models, if the keys are in the ignition when the driver's door is open, it is impossible to lower the door locking pawl on it, and the automation will immediately raise all the locks. This will help avoid such a common situation as accidentally slamming the keys in the lock. Limit switches operate both for opening and closing.
If you turn off the limit switches, the open door indication will stop working. Then problems with the alarm may arise. In addition, there are situations when a light is needed in the trunk or interior.
How to find door switches?
If you don’t know where the door switch is located, then you should start searching for them with a manufactured control or “tseshka”. Signals are removed from the door limit switches - the button principle. This is done in order to protect the car alarm system around the perimeter of the car. When the door is open, the limit switch is not clamped, it is free, and a plus or minus hangs on its wire. But this happens extremely rarely.
First of all, you need to find a wire whose polarity changes and either positive or negative appears when the door is closed or opened.
Most modern cars have a corresponding lamp on the instrument panel that lights up when the door is opened. You need to hook the control crocodiles onto the car body, and use a sting to pierce the wires and observe what the control lamp shows. The key here is to leave only one door open.
As soon as the control lamp lights up green, you need to press the limit switch of the unlocked door or close it completely. If the lamp goes out or lights up red, then we have found the right wire.
In order to make sure that all the doors are connected to one wire, it is necessary, leaving the control on this wire, to open all the doors one by one. If the control lamp does not respond to the ringing of the remaining doors, then this indicates that in this car all the door limit switches are not connected, and it is necessary to find the individual wires remaining from each door using the same method. As a rule, the driver's door and passenger's door switches are unconnected.
Limit switches and their purpose, where they are located in different cars
People who had to deal with the process of independently installing an alarm on a car definitely had to deal with the word limit switch. The instructions say that certain wires must be connected to it. This detail is present on absolutely every old or new car, on the doors and hood of the Grant, Niva, Kalina, Skoda, Logan, Chevrolet, Lanos, Octavia, Sprinter and other vehicles. The operating principle of limit switches is very simple, and the devices themselves are quite small in size, inexpensive, and very easy to connect. They are necessary so that you can correctly open the doors, the hood, use the lighting, and for other purposes that involve the process of enabling or disabling functions.
Troubleshooting door switches
There are often cases when the door switch does not work.
There may be a lot of reasons for this, including dust, clogging and dirt, oxidation, or due to moisture getting inside during the cold season, it simply froze. The fault in this case lies only with the owner of the car, who, due to inattention, was unable to notice the non-working door switches in time. After all, monitoring their operation in each machine is very clear and it is difficult not to notice a non-working condition.
But the solution to this problem today is quite simple - a sealed boot that completely covers the button and does not allow dust, dirt and moisture into this mechanism.
Before you start installing the boot, you need to pierce a cross-shaped notch on its underside where the end switch is attached. After this, you need to install a self-tapping screw in the button hole, then put on the boot and insert a screwdriver through the puncture and secure it to the body. This method surprises with its reliability, simplicity and accessibility.
Popular means
EFELE UNI-M Spray
A universal composition, which is a dispersion of solid lubricating components in mineral oil.
The high anti-wear properties of EFELE UNI-M Spray are due to the combined action of liquid and solid lubricants.
The dispersion contains corrosion inhibitors, and therefore prevents the appearance of rust on car locks and hinges. The lubricant has high penetrating properties and effectively displaces moisture.
Liqui Moly Wartungs-Spray Weiss
Aerosol composition of white color containing microceramic particles. It has good lubricating and water-repellent properties, protects parts from frictional wear and corrosion.
The spray is intended for locks, hinges and other moving mechanisms of cars. The operating temperature range of the lubricant is -30 to +250 C.
Wurth HHS 2000
Aerosol lubricant with increased penetrating properties, excellent adhesion and the ability to harden in a short period of time. Contains synthetic oil, is resistant to washing off with water and high pressure, works at temperatures from -35 to +180 C.
The main disadvantage of the material is its high cost.
Permatex 80075
Colorless composition with a high content of active ingredients. When applied, it turns into foam that penetrates into the most difficult to reach places.
The lubricant was originally intended for chains of motorcycles, bicycles and garden equipment, but experience in its use allowed us to expand this list to include hinges and locks.
The product simultaneously cleans, lubricates and protects parts from corrosion, and prevents dirt and sand from adhering to them.
CRC Multilube
Waterproof universal lubricant spray for hinges. The product contains high-quality mineral and synthetic oils, antioxidant and antifriction additives, and friction modifiers.
The material easily penetrates the friction surfaces of the hinge joints and forms a strong protective film on them. To better control the application process, the lubricant has a bluish tint, which completely disappears after a few days.
How to install an alarm?
Connecting door switches to the alarm system is not a very complicated procedure.
When the door opens, the limit switch closes the black and white wire to ground, and its presence on this wire is a signal that the door is opening. Most alarm systems have such an input and are designated as a “negative door trigger.” But if your chisel is equipped with an APS-4 immobilizer and an injection engine, then the above procedure will not be enough. In addition, you will need to arm the car after the “polite illumination” of the interior lamp or alarm is extinguished, and enable the “delay arming” function (if available). All the methods described are quite acceptable for use.
Wiring check
Instructions for cars of the B0 assembly line (XRAY, Largus, Nissan Almera, Renault Duster, Sandero). Remove the limit switch and set the multimeter to voltmeter mode. We measure the voltage at the contacts of the block with the wires:
- If there is no voltage, the circuit of the interior lamp lamp or the lamp itself is faulty.
- if the voltage is significantly less than 12 V, the wire connecting the sensor to ground is probably damaged.
We set the multimeter to ohmmeter mode, connect one probe to ground (body), and the other to the terminal of the block with the black wire. The resistance should be close to zero. If the resistance is high and tends to infinity, the connection between the wire and the body is probably damaged by corrosion or the wire is damaged (treat the connection with a product to protect electrical contacts). If the fault cannot be resolved in this way, it is necessary to remove the interior trim from the pillar, find and fix the fault.
Door limit switches VAZ 2110
The first sign of non-functioning door switches is the fact that the light does not come on when the door is opened, and the alarm does not arm. This problem is most typical for the tenth generation VAZ.
Door limit switches on the VAZ 2110 fail almost every three years. To avoid such problems, it is necessary to clean these parts annually with sandpaper. In addition, for durability (against oxidation), you can treat them with WD-40 and install anthers.
Problems with limit switches
The most common problem that door switches may encounter is incorrect adjustment.
The cause of such a breakdown may be an unreasonably high installation or too small a stroke of this part. If the alarm is falsely triggered, natural temperature deformations of the trunk or hood lid appear. And if the travel of the limit switch is small, dirt and moisture can get into the gap between the contacts, which also provokes false alarms. Another problem may be the wrong location for installing these parts.
Also, door ends can quickly become corroded and oxidized. Through the filament of the interior light, a positive signal is supplied to the limit switch contact, or the alarm system pulls the input to the positive potential to avoid false alarms. In this case, when condensation gets on the contacts, a low degree of electric current leaks, which will not be enough to trigger the alarm or light the interior lamp. But for such an electrochemical reaction as oxidation-decomposition, metal is enough. After some time, such a limit switch will not work.
What properties should a lubricant for car locks have?
First of all, the lubricant must form a film that protects the inside of the lock from moisture and have water-repellent properties. It should not be washed off with water!
In addition, the composition must withstand exposure to solutions with an alkaline, acid and salt base. Car owners living in big cities know better than anyone else what chemicals public utilities sprinkle on their roads. And what harm do they cause to automobile mechanisms?
A high-quality lubricant should withstand sub-zero temperatures well. And also retain their properties for a long period of time (at least a season, or even two). Possessing such properties, the lubricant reduces the possibility of corrosion on the metal surface of the locking parts.
Also, the lubricant must be a homogeneous mass. Any change in consistency should alert the buyer. After all, even small lumps of unknown origin present in the lubricant can independently clog the larva of the mechanism.
