Battery Checks – 2.5L NA

Overview

The Battery Checks procedure for the Porsche 944 (8-valve engine variants) ensures the battery is in good condition to power the vehicle reliably. This guide covers visual inspections and condition testing to identify issues like corrosion, cracks, or insufficient charge. Regular checks are critical for preventing starting issues and maintaining electrical system health. This guide is tailored for the 1983–1985.5 (Pre-85.5) and 1986–1988 (85.5 Onwards) variants of the Porsche 944 with an 8-valve engine configuration.

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Tools Required

• Wire brush
• Digital multimeter (0.5% accuracy or better)
• Needle-nose vise grips
• 10mm (3/8 inch) wrench for battery clamps

Parts Required

• Petroleum jelly or battery terminal felt rings 944 611 191 00
• Battery cover (Pre-85.5) 944 611 021 00
• Battery cover (85.5 Onwards) 944 611 021 01

Step-by-Step Procedure

Step 1: Perform Visual Inspection

1. Inspect the battery case for cracks or bulges, which indicate a failing battery.
2. Check the battery terminals for corrosion, appearing as white or rust-colored material.

For Pre-85.5 models:

• Ensure the battery cover 944 611 021 00 is in place to minimize corrosion and protect the battery tray.

For 85.5 Onwards models:

• Ensure the battery cover 944 611 021 01 is in place to minimize corrosion and protect the battery tray.

3. If corrosion is present, loosen the battery clamps using a 10mm (3/8 inch) wrench and disconnect the clamps.
4. Clean the battery posts and clamps with a wire brush to remove corrosion.
5. Reconnect the terminal leads securely.
6. Apply petroleum jelly or install battery terminal felt rings 944 611 191 00 to the posts and clamps to reduce future corrosion.

Step 2: Check Battery Condition

7. Disconnect the battery positive lead using a 10mm (3/8 inch) wrench.
8. Measure the no-load voltage of the battery using a digital multimeter with 0.5% accuracy or better.

• If the ambient temperature is below 21°C (70°F), add 0.021 volts to the reading for every 1°C (1.8°F) below 21°C.

9. Compare the voltage to the following table to determine the state of charge:

• 12.75 VDC: 100% charge

• 12.45 VDC: 75% charge

• 12.25 VDC: 50% charge

• 12.05 VDC: 25% charge

• 11.85 VDC: 5% charge

10. Alternatively, observe the interior lights. If they are extremely dim or do not light, the battery lacks sufficient charge to start the engine.
11. Charge the battery for 6–8 hours at 13.8 to 14.6 VDC using an automatic constant voltage charger.

• Avoid charging below 13.8 VDC or above 14.6 VDC to prevent shortening battery life.

• For safe connection, clamp needle-nose vise grips to the positive terminal and attach the charger lead to the vise grips to avoid contact with the windshield frame.

12. After charging, recheck the voltage. Replace the battery if any of the following conditions are met:

• 0 VDC, indicating an open cell.

• 10.0–10.6 VDC, indicating a shorted cell.

• Voltage below 12.45 VDC, indicating the battery cannot hold a charge.

Step 3: Additional Notes for Charging and Jump Starting

13. When connecting a charger or jumper cables:

• Connect in this order: positive terminal of the dead battery, positive terminal of the good battery, negative terminal of the dead battery (preferably a ground away from the battery), negative terminal of the good battery (preferably a ground away from the battery).

• Use needle-nose vise grips on the positive terminal to avoid arcing against the windshield frame.

14. When jump-starting, never use the boost feature on a battery charger, as it can damage the DME computer.

Post Procedure Checklist

• Verify that the battery terminals are clean and free of corrosion.
• Ensure the battery cover is properly installed (Pre-85.5: 944 611 021 00, 85.5 Onwards: 944 611 021 01).
• Confirm the battery voltage is at least 12.45 VDC after charging, indicating a 75% or higher charge.
• Check that interior lights function normally, indicating sufficient battery charge.
• Ensure no arcing occurred during charger or jumper cable connection.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manuals
• YouTube