my Tesla Model S Original (2012-2020) has a hard time starting when hot

Tesla Model S Plaid/Refresh (2021-present)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

3 min read

538 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix starting issues when hot in Tesla Model S (2012-2020). Step-by-step guide with diagnostic procedures and repair instructions.

Affected Component

Electrical

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the 12V battery before working on high-voltage systems to avoid electric shock.
•Allow sufficient time for the battery to cool before servicing to prevent burns or injury.

Symptoms

•Difficulty starting the vehicle when the engine is hot
•Reduced power output during acceleration
•Warning messages on the dashboard related to battery or charging
•Increased electrical system load (e.g., lights dimming)
•Unusual sounds from the battery pack or electric motor

Diagnostic Steps

1
Use an OBD-II scanner to check for any stored error codes related to the battery management system or electric motor.
2
Inspect the high-voltage battery connections for corrosion or loose terminals.
3
Monitor the battery temperature using the vehicle diagnostics to see if it exceeds normal operating ranges.
4
Verify the state of charge (SoC) of the battery to ensure it is within the expected range.
5
Check the performance of the contactors and relays in the battery system for proper operation.
6
Inspect the cooling system for the battery to ensure it is functioning correctly and maintaining appropriate temperatures.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Socket set
•Multimeter
•Wire brush

Parts Required

•Replacement contactors or relays (if needed)
•Battery coolant (if needed)

Related Faults

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Diagnostic Steps

1
Use an OBD-II scanner to check for any stored error codes related to the battery management system or electric motor.
2
Inspect the high-voltage battery connections for corrosion or loose terminals.
3
Monitor the battery temperature using the vehicle diagnostics to see if it exceeds normal operating ranges.
4
Verify the state of charge (SoC) of the battery to ensure it is within the expected range.
5
Check the performance of the contactors and relays in the battery system for proper operation.
6
Inspect the cooling system for the battery to ensure it is functioning correctly and maintaining appropriate temperatures.

Solution

1. Preparation

Ensure the vehicle is parked on a flat surface and turned off.
Gather necessary tools such as a socket set and a multimeter.
Disconnect the 12V battery to ensure safety while working on the electrical systems.

2. Inspect and Clean Battery Connections

Remove the access panel to the high-voltage battery.
Check all battery terminal connections for tightness and corrosion.
- Sub-step: Use a wire brush to clean any corrosion from the terminals.
- Sub-step: Tighten any loose connections to the manufacturer’s specified torque (check service manual for exact values).
Reconnect the battery terminals securely.

3. Test Battery Cooling System

Inspect the coolant levels in the battery cooling system.
- Sub-step: If low, top off with the recommended coolant type (check Tesla specifications).
Check the operation of the battery cooling fans by activating the vehicle's diagnostics mode.
- Sub-step: Ensure the fans run smoothly without excessive noise or vibration.
Replace any faulty fans or cooling components as necessary.

4. Replace Faulty Components

If diagnostic steps indicate defective contactors or relays:
- Sub-step: Remove the faulty components according to the service manual guidelines.
- Sub-step: Replace with OEM parts to maintain system integrity.
Reassemble all components and ensure all connections are secure.