What Are Memory Seats In Cars

So, you're interested in diving deeper into memory seat systems in cars? Good choice. They're more complex than just a button that remembers your spot. Understanding how these systems work can be incredibly useful for diagnosing electrical issues, retrofitting upgrades, or even customizing your seating position beyond factory settings. We're going to break down the components, functionality, and troubleshooting aspects of a typical memory seat system.

Purpose and Relevance

Why bother learning about memory seats? Well, for the DIY enthusiast, understanding this system offers several benefits:

Diagnosis and Repair: When your memory seats stop working, knowing the system's architecture allows you to pinpoint the fault – is it the switch, the motor, the control module, or a wiring issue?
Customization and Retrofitting: Thinking about adding aftermarket seats with memory function? Understanding the system allows you to integrate it properly with the car's existing electronics.
Safety: Familiarizing yourself with the system's components enables you to work on it safely, avoiding potential electrical hazards.

Imagine your memory seat fails right before a long road trip. Knowing the system can guide you through some basic troubleshooting steps to possibly restore functionality or at least bypass the system for manual operation. We even have a downloadable wiring diagram file that will make your task easier. Consider it your roadmap for seat memory success. We will share it later.

Key Specs and Main Parts

At its core, a memory seat system is a mechatronic marvel, blending mechanical components with sophisticated electronics. Here's a breakdown of the critical components:

Seat Position Sensors: These are typically rotary encoders or potentiometers attached to the seat's adjustment mechanisms (forward/backward, up/down, tilt, lumbar support). They convert the seat's physical position into an electrical signal. Think of them as the seat's memory banks, constantly reporting its location.
Seat Motors: Electric motors are responsible for physically moving the seat in various directions. These are usually DC motors controlled by the seat control module.
Seat Control Module (SCM): This is the brains of the operation. The SCM receives signals from the position sensors, compares them to stored memory settings, and then commands the seat motors to adjust the seat accordingly. This module often interfaces with the car's Body Control Module (BCM) or other communication networks.
Memory Switch/Buttons: These are the user interface. Pressing a memory button tells the SCM to recall a specific seat position. They also usually include a 'Set' button to store the current seat position into memory.
Wiring Harness: A dedicated wiring harness connects all these components, providing power and communication pathways. This is where you'll often find connectors, splices, and potential points of failure.

Key specs include the voltage rating (typically 12V DC), current draw of the motors (can be several amps each), and the sensor resolution (the precision with which the seat position is measured). These specs are crucial when diagnosing faults and selecting replacement parts.

Symbols in Wiring Diagrams

Understanding the symbols in a memory seat wiring diagram is crucial for effective troubleshooting. Here are some common symbols you'll encounter:

Straight Lines: Represent wires. Thicker lines usually indicate power wires.
Dotted Lines: Often indicate a shielded wire or a CAN bus communication line.
Circles: Represent components, sometimes with a letter inside to indicate the type of component (e.g., 'M' for motor, 'S' for switch).
Rectangles: Commonly used for control modules or relays.
Resistors: Represented by a jagged line or a rectangle with a resistor symbol inside.
Ground Symbol: Usually represented by three horizontal lines decreasing in size, indicating a connection to the vehicle's chassis ground.
Color Codes: Wires are often labeled with color codes (e.g., "RD" for red, "BL" for blue, "BK" for black) to help identify them in the wiring harness.

Color coding is critical! Never assume a wire is providing the proper input or output just because it looks similar. Always double-check against the wiring diagram.

How It Works

The memory seat system operates in a closed-loop feedback control system. Here's a simplified breakdown of the process:

User Input: The driver presses a memory button (e.g., "Memory 1").
SCM Activation: The Seat Control Module (SCM) receives this signal.
Memory Recall: The SCM retrieves the seat position values stored for "Memory 1" from its internal memory (typically EEPROM - Electrically Erasable Programmable Read-Only Memory).
Position Comparison: The SCM compares the stored position values with the current seat position reported by the seat position sensors (rotary encoders/potentiometers).
Motor Activation: Based on the comparison, the SCM sends signals to the appropriate seat motors to adjust the seat. The SCM controls the direction and duration of motor operation. Pulse Width Modulation (PWM) is often used to control the motor speed.
Feedback Loop: As the seat moves, the position sensors continuously update the SCM with the new seat position. The SCM monitors these signals to ensure the seat is moving towards the desired position.
Target Position Reached: Once the seat reaches the target position (as determined by the SCM), the motors are deactivated.

Real-World Use - Basic Troubleshooting Tips

Let's say your memory seat is acting up. Here are some basic troubleshooting steps you can take:

Check the Fuses: This is always the first step. Consult your owner's manual or a wiring diagram to identify the fuse(s) associated with the memory seat system.
Inspect the Wiring Harness: Look for any signs of damage to the wiring harness under the seat. Check for loose connectors, frayed wires, or corrosion.
Test the Memory Buttons: Use a multimeter to check if the memory buttons are sending a signal to the SCM when pressed.
Listen for Motor Activity: When pressing a memory button, listen for any sound coming from the seat motors. If you hear clicking but no movement, it could indicate a faulty motor or a jammed mechanism.
Scan for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to check for any DTCs related to the memory seat system. This can provide valuable clues about the source of the problem.
Check the Seat Position Sensors: Using a multimeter, check the resistance or voltage output of the seat position sensors as you manually move the seat. This can help determine if the sensors are functioning correctly.

For example, if the seat moves in some directions but not others, the problem is most likely a specific motor or its associated wiring. If none of the memory functions work but manual adjustments do, suspect the control module or its power supply.

Safety Considerations

Working on a memory seat system involves dealing with electrical components. Here are some crucial safety precautions:

Disconnect the Battery: Always disconnect the negative battery terminal before working on any electrical components in the car. This prevents accidental shorts and potential injuries.
Be Careful with Airbag Wiring: Some vehicles have side airbags integrated into the seats. Be extremely careful when working near the airbag wiring. Follow the manufacturer's instructions for disabling and disconnecting the airbag system.
Avoid Shorts: Use caution to avoid shorting any wires. This can damage electrical components and potentially start a fire.
Use Proper Tools: Use insulated tools and test equipment to avoid electrical shocks.
Consult a Professional: If you're not comfortable working with electrical components or if you're unsure about any aspect of the repair, consult a qualified mechanic.

The airbag system is a serious safety concern. Improper handling can lead to accidental deployment, which can cause severe injury. Always follow the manufacturer's safety procedures.

Conclusion

Memory seat systems are complex, but with a solid understanding of their components and operation, you can effectively diagnose and repair issues. Remember to always prioritize safety and consult a professional when needed. Armed with this knowledge, you're well-equipped to tackle memory seat challenges. And to make your task even easier, we have prepared a detailed wiring diagram. Please reach out to us with the make and model of your car, and we'll happily provide you with a tailored version to help you with any repairs, learning, or modifications you plan to undertake. Good luck!