How to Replace the Battery on a 1991 BMW Step-by-Step

The battery is under the back seat in most 1991 BMWs.

Switching out the battery in your BMW should only take a few minutes to accomplish. The battery is located under the backseat. You will want to change the battery every four years, as this is the life span on most batteries. While you are changing the battery on your BMW you will want to ensure any corrosion is cleaned from the battery cables. Scrub an abrasive brush on the battery cables until all the white substance is removed. This will help to ensure you get the best performance from your new battery.

Things You'll Need

• Socket wrench
• Socket set
• Crescent wrench
• New battery

Instructions

1. Lift the back seat up and pull it out of the car. You will just need to move the bottom portion of the back seat.

2. Unbolt the clamp holding the battery in place with a socket wrench. Depending on the model there will be one or two clamps holding the battery in place.

3. Unscrew the negative cable with a crescent wrench. Repeat to loosen and remove the positve cable as well.

4. Lift the battery out from the seat compartment. The battery should come right out.

5. Place the new battery in the place of the old one. Ensure the terminals are facing the same way as the old one.

6. Tighten the negative and positive cables to the terminals. Ensure the black is connected to the post indicated by a "-" sign. The positive is colored red and indicated by a "+" sign.

7. Bolt the bracket down over the battery. This will secure the battery in place.

8. Place the seat back in to place. It will need to clip in place to secure it correctly.

9. Start the car to ensure the battery is functioning correctly. Turn the car off and allow it to sit overnight and start the car in the morning. This will indicate if the battery is holding a charge.

Tips & Warnings

• Replace the alternator if the car is still acting like the battery is dead.

• Use extreme caution when working on the electrical system. Do not connect the battery cable to the wrong terminal. This can cause serious damage to the vehicle and an electrical shock to you.

• Contact your automotive parts store or the store you purchased the battery from for disposal of the old one.

References

• Americredit: Tutorial on Changing a Car Battery
• "BMW 3 & 5 Series Haynes Repair Manual covering 318i (1984 and 1985), 325/325e/325es (1984 thru 1988), 325i/325is/325iC ( 1987 thru 1991), 525i (1989 and 1990), 528e (1982 thru 1988), 533i (1983 and 1984), and 535K/535is (1985 thru 1992) for gasoline engines and two wheel drive models"; John Haynes; 1992