Longview High School Automotive Club

08/07/2026

08/06/2026

Jump-start your career with the world class support of Matco Tools.

08/06/2026

⚡ What Do Relay Terminals 30, 85, 86 & 87 Mean?

Automotive relays are small but essential electrical switches used in almost every modern vehicle. They allow a low-current control circuit to safely operate a high-current component such as the starter motor, fuel pump, cooling fan, headlights, horn, or air conditioning compressor. Understanding the function of relay terminal numbers 30, 85, 86, and 87 makes diagnosing electrical problems much easier.

🔴 Terminal 30 – Battery Power (+12V)
Terminal 30 is the main power supply for the relay. It receives direct battery voltage, either through a fuse or directly from the battery. This terminal always carries the high-current power that will eventually be sent to the electrical component when the relay is activated.

🔵 Terminal 85 – Coil Ground (-)
Terminal 85 is one side of the relay's electromagnetic coil. In most automotive applications, it is connected to ground (negative). When current flows through the coil, it creates a magnetic field that pulls the internal switch closed. Some circuits switch the ground through the ECU instead of connecting it directly.

🟢 Terminal 86 – Coil Positive (+)
Terminal 86 is the positive trigger for the relay coil. It usually receives 12 volts from the ignition switch, ECU, sensor, or control switch. When voltage is applied to terminal 86 while terminal 85 has a ground connection, the relay energizes and closes the internal contacts.

🟠 Terminal 87 – Output to the Load
Terminal 87 is the output terminal. Once the relay is energized, the internal switch connects terminal 30 to terminal 87, allowing battery voltage to flow to the electrical device. This could power a radiator fan, fuel pump, headlights, or many other high-current components.

How the Relay Works

When the control circuit sends power to 86 and ground is present at 85, the relay coil becomes energized. The magnetic field closes the internal contacts, connecting 30 to 87. As a result, battery power flows to the connected component. When the control signal is removed, the magnetic field disappears, the contacts open, and power to the component stops.

Why This Knowledge Matters

Understanding relay terminal numbers helps mechanics and vehicle owners diagnose no-start conditions, fuel pump failures, cooling fan problems, headlight faults, and other electrical issues. Instead of replacing expensive parts unnecessarily, you can quickly test for battery voltage, ground, trigger signals, and output using a multimeter. Mastering these four relay terminals is one of the most valuable skills in automotive electrical diagnostics and can save both time and repair costs.

Dr.mechanics

08/02/2026

Fuel Injection System Sensors – The Hidden Heroes of Engine Performance

Modern engines rely on a network of sensors to provide the Engine Control Unit (ECU) with accurate, real-time information. These sensors continuously monitor engine operating conditions, allowing the ECU to adjust fuel delivery, ignition timing, and air-fuel ratio for maximum performance, fuel economy, and reduced emissions.

The Oxygen (O₂) Sensor measures the oxygen content in the exhaust gases. This helps the ECU maintain the correct air-fuel mixture. A faulty O₂ sensor can cause poor fuel economy, rough idling, increased emissions, and may trigger fault code P0130.

The MAP (Manifold Absolute Pressure) Sensor monitors intake manifold pressure to calculate engine load. If it fails, you may experience hesitation, poor acceleration, hard starting, or reduced engine performance.

The Engine Coolant Temperature (ECT) Sensor reports coolant temperature to the ECU. Incorrect readings can result in difficult cold starts, excessive fuel consumption, overheating issues, or cooling fan problems.

The Knock Sensor detects abnormal combustion, commonly known as engine knock or detonation. When knock is detected, the ECU adjusts ignition timing to protect the engine. A failed knock sensor can reduce power and increase the risk of engine damage.

The Throttle Position Sensor (TPS) monitors the position of the throttle plate. This information is essential for smooth acceleration and idle control. A defective TPS may cause hesitation, unstable idle, delayed throttle response, or transmission shifting issues.

The Fuel Pressure Sensor measures fuel rail pressure to ensure the injectors receive the correct fuel supply. Incorrect pressure readings can lead to hard starting, poor performance, loss of power, or even a no-start condition.

Understanding the function of these sensors is essential for accurate diagnostics. Replacing parts without proper testing often wastes time and money. Always scan for diagnostic trouble codes, inspect live data, and verify sensor operation before replacing any component. Accurate diagnosis is the key to efficient, reliable, and professional automotive repair.

Dr.mechanics

08/01/2026

🚘 The Evolution of Ford Cars (1930–1950) | 20 Years of American Automotive History


Caption:
From the iconic 1930 Ford Model A to the stylish 1950 Ford Custom Deluxe, explore two decades of legendary American automotive design. 🚘🇺🇸 Every generation brought new looks, improved performance, and timeless classic style.

07/31/2026

In August 1950, a man named Harmon Dobson opened a small stand in Corpus Christi selling a twenty-five cent burger that was different on purpose.

A quarter pound of fresh beef on a five-inch bun, built to take two hands to hold, at a time when most burgers fit in your palm.

He wanted people to take one bite and say what a burger, and the name stuck.

That stand grew into a Texas institution that never left home. 🔥

07/18/2026

Mind blown.