There are more than a hundred light bulbs in a modern car. The tasks are different, ranging from interior lighting, instrument panel to ensuring the visibility of the road at night. Depending on these goals, the lamps also have different dimensions, electrical characteristics, and a mounting base. It is about the base of automotive lamps that we will talk in this article.

A socle is a structural element of the lamp holding it in the cartridge, as well as an element transmitting current to power the lamp through its contacts (platforms, petals, wire leads). Also, the cap has another important task, this is sealing the bulb of the lamp from the external environment. In many automotive lamps, especially high-power lamps (low and high beam, fog) gas is pumped. The base must ensure tightness throughout the life of the lamp, in order to exclude its exit from the bulb. In addition, in conventional incandescent lamps there is a vacuum, which is also hermetically isolated from the external environment by a cap.
With the advent of LED lamps, a function such as sealing has become a rudiment, but not all lamps and not all cars have got rid of the classic incandescent lamp.

Types and designation of automotive lamps and socles
At the dawn of the automotive industry, the designation of lamps, the use of socles was chaotic, each of the manufacturers used, as it seemed to him, the best. As a result, the number of types of bulbs tended to infinity. Today, the defining standard for lamp manufacturers in our country is GOST 2023-88. Of course, and it is not perfect, since progress is not worth it, but GOST 88, nevertheless, most automotive lamps and socles are described in it.
Depending on the number of contacts at the lamp base, the corresponding letter is added
s - one contact
d - two contacts
t - three contacts
q - four pins
p - five pins

Types of lamp caps

A - a car lamp.
AMN - car miniature lamp.
AC - automotive spotlight.
ACG is a quartz halogen automotive lamp.
T - miniature lamp base. The cap is made in conjunction with the bulb. Example designation for an example (T5 4W) - a lamp with a diameter of 5/8 inches, power 4 watts.
R - a lamp with a metal base of 15 mm and a bulb in 19 mm. The designation for an example (R 5W) is a power of 5 watts.
R2 - Flask diamter of the order of 40 mm. Incandescent lamps used in Soviet times for high and low beam. At the moment, almost never used.
P - lamp with a 15 mm socket and bulb diameter up to 26.5 mm. Designation for example (P21W) - 21 watts.
SV (C) - spotlight (on both sides there is a base). As a rule, it is used for interior lighting, license plate illumination. Designation for example SV8.5 5w– the lamp has a base diameter of 8.5 mm, power 5 watts. May be designated as C5W.
VA is a pin-type lamp in which each pin is located symmetrically relative to the others.
BAY - a pin lamp in which one of the pins is offset in height.
BAZ - pin lamp with offset pin in height and radius.
W - lamp base made in conjunction with a glass bulb. Example of designation (W 2 * 4,6d 5W) - the base is made together with a bulb made of glass, the base is 2 mm thick, 4.6 mm wide, 2 contacts, power 5 watts.

Designation of lamps not on the base

The most common halogen lamps can have a different base, but start with the same letter H, which means halogen. There are also digital values that also indicate the unique shape and base of the lamp, for example 9145 (fog lamp).

Designation of lamps by light

Y - if the letter is behind the first character, then this lamp is made with the orange color of the bulb. Designation for example (PY21W) - lamp with a socket 15 mm, bulb 26.5 mm, with an orange bulb.
The following is a drawing in which you can compare the description above with the appearance of a car lamp and a socle


lamp H1 base P14.5s
lamp H2 base X511
lamp H3 base PK22s
bulb H4 socket P43t
lamp H7 base PX26d
lamp H11 base PGJ19-2
bulb H8 socket PGJ19-1
bulb H9 socket PGJ19-5
bulb H12 socket PZ20d
bulb H10 socket PY20d
bulb HB3 socket P20d
HB4 lamp base P22d
lamp D1S socket PK32d-2
lamp D1R socket PK32d-3
bulb D2S socket P32d-2
bulb D2R socket P32d-3
lamp PY21W socket base BAU15s
bulb P21W socket BA15s
lamp P21 / 4W socket BAZ15d
lamp P21 / 5W socket BAY15s
bulb R5W socket BA15s
bulb R10W socket BA15s
lamp T4W socket BA9s
lamp W5W socket W2.1x9.5d
lamp W3W socket W2.1x9.5d
lamp W2.3W socket W2x4.6d
lamp WY2.3W socket W2x4.6d
lamp WY5W socket W2.1x9.5d
bulb H6W socket BAX9s
lamp H21W socket BAY9s
lamp C5W socket base SV8.5-8
lamp HB1 socket P29t
lamp HB5 socket PX29t
bulb WP21W socket WZ2.5x16d
lamp P27W socket WZ2.5x16d
lamp C21W socket base SV8.5-8
lamp W21W socket W3x16d
lamp W21 / 5W socket W3x16q
bulb W16W socket W2.1x9.5d
bulb WP21W socket WY2.5x16d
lamp PY27 / 7w lamp base WX2.5x16q