ASE A4 Suspension and SteeringWheel Alignment Diagnosis, Adjustment, and RepairMedium
An alignment machine is being operated by a technician. During the runout compensation procedure, the machine prompts the technician to 'Rotate wheel 90 degrees and press enter' multiple times, but the measurements consistently fail to register or produce inconsistent readings. What is the MOST likely cause of this issue?
- ALoose or improperly mounted alignment sensors/targets.
- BIncorrect tire pressure in one of the wheels.
- CA faulty brake pedal depressor preventing wheel rotation.
- DExcessive vehicle weight causing sensor slippage.
Show answer & explanationAnswer & explanation
Correct answer: A. Loose or improperly mounted alignment sensors/targets.
Runout compensation requires precise measurement as the wheel is rotated. If the sensors or targets are loose, vibrating, or improperly mounted, the machine will fail to get accurate readings during rotation, leading to failed compensation or inconsistent results.
Why the other options are wrong
- B. Incorrect tire pressure can affect alignment angles but would not typically cause a failure to register or inconsistent readings *during* the runout compensation procedure itself.
- C. A faulty brake pedal depressor would prevent the wheels from being rotated at all, not cause inconsistent readings during rotation.
- D. Excessive vehicle weight is unlikely to cause sensor slippage during runout compensation; sensor mounting is designed to handle this.
Runout Compensation Failure
Runout compensation calibrates the alignment sensors to account for wheel and adapter imperfections. Failures often stem from unstable sensor mounting or issues during wheel rotation.
- Compensates for wheel/adapter runout.
- Requires stable sensors and smooth wheel rotation.
- Loose sensors are a primary cause of failure.
Memory trick: Runout's turn, if sensors shake, faulty readings it will make.