What is Ural-Auto 2 and why does its wiring diagram raise questions?

Trucks Ural-Auto (in particular, the model Ural-4320-31 and its modifications, often called β€œUral-Auto 2”) is a legendary technique that combines the reliability of the Soviet engineering school and modern requirements for cargo transportation. However, their electrical circuit remains one of the most confusing for mechanics. Unlike foreign cars, where the wires are marked according to the standard DIN, it uses a unique designation system inherited from military designs.

The main problem of the owners is lack of official documentation freely available. Even in service manuals, diagrams are often given in fragments, without explanations color coding of wires in different production batches (before 2010 and after 2015 it is different!). This article will help you understand the nuances: from the location of fuses to diagnosing typical β€œglitches” of the on-board network.

We analyzed diagrams from factory catalogs, reviews from electricians from forums Drive2 and UralAZ-Club, as well as manufacturer's technical bulletins. The result is a practical guide that will be useful for both beginners and professionals.

General structure of the electrical circuit: key components and their purpose

Electrical wiring Ural-Auto 2 built on a modular principle, where each block is responsible for a specific system. Main components:

  • πŸ”‹ Rechargeable battery (24V) β€” two 12V batteries connected in series, located under the cabin.
  • ⚑ Generator G-288 (or modifications) with a built-in voltage regulator - produces up to 28V at 3000 rpm.
  • πŸ“¦ Fuse and relay box (main and additional) - located behind the instrument panel, to the left of the steering wheel.
  • πŸš— Central switching unit (CBB) β€” the β€œbrain” of the system, which controls signals from sensors.
  • πŸ’‘ Lighting devices β€” headlights, dimensions, brake lights with separate wiring for the trailer.

Feature of the scheme - duplication of critical circuits (for example, the fuel pump is powered through two independent fuses). This is a military legacy where resiliency is paramount. However, this solution complicates troubleshooting: if one circuit shorts, the second may mask the problem.

πŸ“Š Which Ural-Auto 2 electrical system do you most often have problems with?
Starter and charging
Lighting and signals
Instrument panel
Additional equipment (winch, PTF)
Another problem

It is important to understand that the diagram is divided into power and manager parts. Power wires (4–6 mmΒ² thick) are usually red or black, and control wires (0.75–1.5 mmΒ²) are multi-colored. This helps visually separate high-voltage circuits from signal circuits.

Pinout of connectors and color marking of wires

The most difficult moment for repairmen is mismatch of wire colors in different batches. For example, in cars before 2012 yellow wire could mean β€œground”, and after 2015 - β€œtemperature sensor signal”. Below is the current table for most modifications Ural-4320-31 (after 2010 release):

Wire color Purpose Typical location
Red Plus 24V (constant) From battery to fuse box
Black Weight (minus) Body, frame, engine
Blue Control signal (for example, turning on headlights) From switches to relays
Yellow-green Pressure/temperature sensors From engine to dashboard
White with red stripe Power supply after ignition switch From the lock to the relay block

To accurately identify a wire, use multimeter in dialing mode. For example, to find the plus after the ignition switch:

  1. Turn on the ignition (without starting the engine).
  2. Connect one multimeter probe to "+" battery.
  3. Using the second probe, touch the wires in the relay block connector one by one.
  4. The desired wire will show voltage 23–25V.
πŸ’‘

If on your Ural-Auto 2 The colors of the wires do not match the table, take a photo of all connectors before disassembling. This will save you hours of reassembly!

Typical electrical faults and methods for diagnosing them

According to statistics from service centers, 70% of problems are electrical Ural-Auto 2 connected to three nodes: generator, relay block and instrument panel. Let's look at each category in detail.

1. Problems with battery charging

Symptoms: The charging lamp is constantly on or the batteries are discharged overnight.

  • πŸ” Check the alternator belt - it should bend no more than 10 mm when pressed.
  • πŸ”§ Generator test: When the engine is running, the voltage at the battery terminals should be 27–29V.
  • πŸ”Œ Oxidation of contacts on the positive wire from the generator to the battery - clean with sandpaper.

2. Instruments on the panel do not work

A common reason is blown fuse F10 (10A) in the main block. But if the replacement did not help:

  • πŸ“Š Check it out connector X2 on the back of the panel - contacts often come off there.
  • πŸ”„ Reset errors: Disconnect the battery for 10 minutes, then connect again.

3. Short circuit in the lighting circuit

If when you turn on the headlights it works main fuse (30A), look for a short circuit in the wires going to:

  • πŸ’‘ Headlight block (check lamps and sockets for moisture).
  • πŸš› Trailer connector β€” the insulation there is often frayed.
How to find a β€œfloating” fault?

If the problem appears intermittently (for example, the headlights flicker on bumps), use the β€œwiggle” method: turn on the faulty circuit and wiggle all the connectors and harnesses. The place where the contact is lost is the source of the problem.

For diagnostics use tester with break detection function (for example, MS8229). Connect it to ground and test each wire in the suspect circuit.

Step-by-step instructions: how to test a circuit with a multimeter

To test circuits Ural-Auto 2 you will need a multimeter with modes voltmeter (200V), ohmmeter (200Ξ©) and calls. Follow the algorithm:

Disconnect the ground from the battery|Remove the protective covers from the unit being tested|Clean the contacts from oxides (use WD-40)|Prepare a diagram (print or open on your phone)-->

Step 1: Check Wire Continuity

Switch the multimeter to dialing mode (diode icon). Connect the probes to the ends of the wire:

  • πŸ”Š Beep β€” the wire is intact.
  • 🚫 No signal - break (look for the fracture site).

Step 2: Finding the Short Circuit

Disconnect the wire from the power and check the resistance between it and ground:

  • πŸ“‰ 0Ξ© - short circuit.
  • πŸ“ˆ More than 10kΞ© - the chain is OK.

Step 3: Check Voltage

Turn on the ignition and measure the voltage on the suspect wire relative to ground:

  • πŸ”‹ 24V - there is food.
  • πŸ”Œ 0V - Check the fuse or relay.
  • ⚑ 12V β€” one of the batteries in the circuit may break.
πŸ’‘

If the multimeter shows 12V instead of 24V, never connect a load (for example, a starter)! This is a sign that the batteries are unbalanced, which can lead to a fire.

Where can I download the official diagrams and how to read them?

Official wiring diagrams Ural-Auto 2 distributed through dealerships or service manuals. However, there are legal ways to get them for free:

  • πŸ“„ UralAZ website - in the section "Technical documentation" (registration required).
  • πŸ“± Mobile application "UralAZ Service" β€” diagrams in PDF format with search by part numbers.
  • πŸ’¬ Forums - on Drive2 and UralAZ-Club post scanned pages from factory catalogs.

When reading the diagrams, pay attention to:

  1. Contact numbers (for example, X1:5 β€” connector X1, pin 5).
  2. Legend:
    • πŸ”Ή β€”| |β€” - capacitor.
    • πŸ”Ή β€”[ ]β€” - fuse.
    • πŸ”Ή β€”( )β€” - relay.
  • Color coding - on the diagram it is indicated by a letter code (for example, F - yellow, K - red).
    • πŸ’‘

    If the diagram is in English, use a translator with text recognition function (for example, Google Lens). Many notations (for example, IGN - ignition) are standard for all cars.

    For convenience, print the diagram on plottere at a scale of 1:1 - this will help compare it with the actual wiring in the car.

    Electrical modernization: what can be improved?

    Standard scheme Ural-Auto 2 designed for a minimum set of equipment. When installing additional devices (winches, refrigerators, inverters), overloads occur. Let's look at the proven improvements:

    1. Installation of an additional relay block

    Problem: the standard unit is not designed for the high currents of modern LED headlights or a winch.

    Solution: installation separate relay for 40–50A powered directly from the battery. Example diagram:

    

    Battery (+) β†’ Fuse (50A) β†’ Relay (87) β†’ Load
    

    Ignition (+) β†’ Relay (86) β†’ Ground (85)

    2. Replacing standard wiring with multi-core wiring

    Standard wires Ural-Auto - single-core, which leads to their fragility when bending. Replace them with stranded wires with a cross section of 2.5 mmΒ² (for power circuits) and 0.75 mmΒ² (for signal).

    3. Installing a voltage stabilizer

    Voltage surges in the on-board network (from 22V to 30V) are detrimental to electronics. Solution - DC-DC converter (for example, Mean Well SD-50A-24), which produces stable 24V.

    πŸ“Š Are you planning to upgrade the electrics of your Ural-Auto 2?
    Yes, soon
    Yes, but later
    No, I'm happy with everything
    Already done
    ⚠️ Attention: When upgrading, never connect additional consumers to the standard lighting or ignition relays! This will lead to overheating of the contacts and a fire. All new devices must be powered via separate fuses.

    FAQ: answers to frequently asked questions

    Where is the fuse box on Ural-Auto 2?

    The main unit is located behind the instrument panel, to the left of the steering column. Additional unit (if any) - under the hood, next to the batteries. To get to the main block, you need:

    1. Unscrew the two screws securing the bottom panel (under the steering wheel).
    2. Disconnect the instrument lighting connector.
    3. Remove the plastic block cover.

      4. The fuse location diagram is usually pasted on the back of the cover.

    Why do the headlights often light up on Ural-Auto 2?

    Main reasons:

    • πŸ”Œ Power surges from a faulty generator (check the relay regulator).
    • πŸ’§ Moisture ingress into the headlight units (the seals become tanned over time).
    • πŸ”‹ Vibration β€” when off-road, the lamp filaments fray. Solution: install LED lamps with vibration-resistant mounts.
    Which multimeter is best to use for diagnostics?

    To work with Ural-Auto 2 A multimeter with the following characteristics is suitable:

    • πŸ“Š Measuring range: up to 200V (DC) and 200Ξ©.
    • πŸ”Š Dialing function with a sound signal.
    • πŸ”‹ Overload protection (at least 1000V).

    Recommended models: Mastech MS8229, Fluke 101, or UNI-T UT33D.

    Is it possible to use the circuit from Ural-4320 to repair Ural-Auto 2?

    Partially you can, but with reservations:

    • βœ… Power circuits (starter, generator, batteries) are identical.
    • ⚠️ Control circuits (instrument panel, ECU) may differ - in Ural-Auto 2 Often another relay block is installed.
    • 🚫 Lighting scheme in Ural-Auto 2 modified to European standards (separate dimensions and brake lights).

      • It is better to find a diagram specifically for your modification (the number is indicated in the PTS).

    What to do if the appliances do not work after washing the car?

    Most likely, water got into instrument panel connectors or relay block. Follow the algorithm:

    1. Disconnect batteries.
    2. Remove the instrument panel and blow out the connectors compressed air (at least 5 atmospheres).
    3. Process contacts spray for electronics (CRC 2-26).
    4. Dry for 24 hours (you can use a hairdryer at minimum temperature).
    ⚠️ Attention: Never turn on the ignition until you are sure that the moisture has completely evaporated! This may burn the control unit.