To effectively diagnose why the key won't turn in your 1990 BMW 325is, start with the simplest solutions before progressing to more complex assessments. Begin by checking the steering wheel lock, as a locked steering wheel can prevent the key from turning. Gently wiggle the steering wheel while attempting to turn the key to see if this resolves the issue. If that doesn't work, apply a lubricant like WD-40 into the keyway to address potential corrosion or sticking components. Next, inspect the ignition lock cylinder; if the key turns to the accessory position but not further, there may be internal damage or wear. For a closer examination, remove the steering column trim and the lock cylinder, using a paperclip to release it while the key is in position one. If the lock cylinder appears intact, shift your focus to the ignition switch, which may require removal of the steering wheel and lower plastic housing for access. Check the switch's functionality by turning it with a flat screwdriver. If the key turns but the car doesn't start, investigate the wiring around the ignition switch for any electrical issues. As a last resort, if you cannot obtain a working key, you might consider shorting the ignition wires, but this is not recommended due to potential security and operational risks. By following this diagnostic approach, you can systematically identify the root cause of the problem and take appropriate action.

When dealing with a 1990 BMW 325is where the ignition key won't turn, it's essential to understand the common problems that could be at play. One frequent issue is the ignition lock cylinder, which can wear out or jam over time, often accompanied by a grinding sensation when attempting to turn the key. Additionally, the steering wheel lock mechanism may engage incorrectly, so gently wiggling the steering wheel while turning the key can sometimes help release it. Electrical or mechanical failures within the ignition switch can also prevent the key from moving past certain positions, indicating a need for further inspection. Internal components, such as pins or dowels within the ignition lock housing, may break or become dislodged, leading to a jammed mechanism. While less common, a worn or damaged key can contribute to the problem, especially if multiple keys fail to work. Furthermore, issues with the column lock assembly may necessitate disassembly for repair or replacement. Lastly, misalignment or blockages, such as debris in the shifter mechanism, can indirectly affect the ignition system. By carefully disassembling and inspecting these components, DIY enthusiasts can identify and address the specific issue preventing the ignition key from turning.