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AM Restrictor

AM reception has been improved on the F01/F02.

Due to the great distances with relatively few radio broadcasting towers, in less populated areas of the US AM radio is more accessible than FM radio.

Interference frequencies from the vehicle electrical system pose reception problems in terms of the quality of AM radio. In an unrestricted antenna system, these interference frequencies spread from the vehicle electrical system through the power supply to the rear window defogger into the antenna system.

The AM restrictor was specially developed to address this issue.

The AM restrictor supplies voltage to the upper section of the rear window. In addition, the rejector circuit components provide sound quality filtering.

The main component is a coil which acts as an extremely high resistance to RF signal, resulting in significantly improved AM reception.

Fig 1: Identifying AM Restrictor Components
G06925511Courtesy of BMW OF NORTH AMERICA, INC.
INDEX REFERENCE CHART

Index Explanation
1 Interference suppression coil for AM range
2 Positive supply to rear window
3 Positive supply from vehicle wiring harness
4 Ground supply from vehicle wiring harness
5 Ground supply to rear window