Magnet myths explained for cars: sensors, radar and electronics

|Paul Calinoiu
Red Mazda car on a road with a cityscape in the background

TLDR

  • Permanent magnets create static magnetic fields with 0 Hz frequency. Automotive radar uses radio waves in the 76–81 GHz band. These are different phenomena.

  • Parking sensors are ultrasonic around 40 kHz, again a different technology.

  • Real issues come from blocking or altering the radar window. OEM manuals explicitly warn against stickers or accessories over that area.

  • For people with implanted cardiac devices: keep strong magnets away from the chest, commonly about 6 inches.

Why these myths persist

Three unrelated domains get conflated online:

  1. Static magnetic fields from permanent magnets.

  2. Electromagnetic waves used by automotive radar.

  3. Ultrasound used by parking sensors.

A permanent magnet does not transmit radio energy. A 77 GHz radar does, and an ultrasonic sensor sends sound. Mixing the three leads to confusion that magnets are “jammer-like.” They are not.

Automotive radar, the right mental model

Most modern automotive radars operate in the 76–81 GHz band. High frequency means compact antennas and high resolution. The radar unit often sits behind the emblem, grille or bumper, looking through a plastic radome designed for minimal RF loss. Putting unapproved materials or accessories in front can attenuate or deflect the beam, which is why owner’s manuals say to keep that area clear.

Parking sensors are ultrasound, not RF

Typical park assist sensors use ultrasound near 40 kHz. Static magnets do not affect how air carries sound. False alarms tend to come from dirt, ice, odd reflections or bumper geometry, not from a stationary magnetic field.

What actually degrades sensor performance

  • Obstruction: any object placed over the radar window or nearby can block or scatter the beam. OEM manuals call this out.

  • Wrong material in front: radar energy passes through certain plastics, while others can severely attenuate it.

  • Damage or deformation around the sensor location.

  • Weather and contamination on the sensor region.

None of the above is caused by using a magnetic plate holder per se. It is caused by blocking the radar’s field of view or altering the material stack in front of it.

What static magnets do not do

  • They do not transmit RF energy.

  • They do not “jam” 77 GHz radar, because a static field has no oscillation and does not radiate.

  • They do not disturb cameras.

  • They do not detune ultrasonic sensors, which are based on sound waves, not RF.

Legit concerns, answered

1) Is it fine to run magnets on a car with ACC and AEB?
Yes, provided you do not place anything over the radar window and you keep that area clean as the owner’s manual requires.

2) Can magnets mess with park sensors?
No, not electromagnetically. Cleanliness, ice, dirt and odd reflections are the usual suspects.

3) What about people with pacemakers or ICDs?
Strong magnets close to the chest can trigger special modes in implantable devices. The FDA advises keeping consumer devices with magnets about 6 inches away from implants. In a car context, bumper-mounted magnets are far from the torso, yet personal precaution is wise.

4) Temperature and stability
Magnet performance decreases at elevated temperatures. Our systems are specified for −30 °C to +60 °C, a practical range for real-world driving and the plastics used.

5) Corrosion
We use zinc plus black epoxy finishes for enhanced corrosion resistance and a distinct premium look.

What this means for your SleemPlate choice

  • MagSleem and MagSleem X use a localized magnet–magnet pairing, secured with screws to the car. Bumper material does not affect retention because the clamping is magnet to magnet, not magnet to steel.

  • SuperSleem contains no magnets and offers an ultra-slim profile.

  • No adhesives are supplied in the kits. IPA wipes are included for surface cleaning.

  • If in doubt on an ADAS-heavy bumper, simply leave the radar zone unobstructed and refer to the vehicle manual.

Mounting dos without a step-by-step

  • Do not mount anything directly over a radar window.

  • Keep ADAS-marked regions clear.

  • After harsh weather or washing, wipe the sensor zones clean.

  • If ADAS warnings appear, check for dirt or ice and see a dealer if messages persist.

Bottom line

Permanent magnets are not RF emitters. They do not “jam” radar or confuse ultrasonic sensors. Real problems come from blocking the radar’s view or changing the material in front of it. Keep radar windows clear, respect OEM placement for plates, and you will be set for a quiet, consistent ADAS experience.