Thread: 302 Stroker??

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Ferrite beads are what we call "Gremlin Catchers", they're used on most electronics now days, you'll often see one on the power cord and other cables on your computer (the bulge in the cord). Basically they trap and store unwanted frequencies (A/C).

Most likely at the higher speeds the fans are forced to turn faster than their motor will allow (sometimes referred to as the generator effect), this can cause the brushes to arc on the commutator producing A/C frequencies that can interfere with sensitive equipment.

The ferrite bead, either applied to the sensitive equipment (speedo) or the the source equipment (fans) will absorb the phantom frequencies and store them until the equipment is turn off. Ferrite beads are usually applied to one (sometimes both) wire of the equipment, usually the wire goes through a hole in the bead (bead slips over the wire’s insulation), the bead does not physically contact the wire electrically (leave the insulation on the wire), rather it works by inductance.

Ferrite beads come in all sizes, you’ll find them online. Check with your speedo manufacture for a size (frequency range) they recommend. Slip the bead over the wire tape it in place and it’s done.

Originally Posted by rspears

What I don't understand is how this "frequency feedback" travels without a complete loop. At 75mph your fan is not needed, and the thermostat/controller would be open, eliminating the path for 12v power to the fan motor. The fan is freewheeling, but the path back to the electrical system is blocked by an open switch, either a physical contact or an electronic switch in a controller. How does this feedback get to the other components if the fan is OFF?

I only control the ground side with the relay! The positive side goes right back to the main power connection, aka battery.

Originally Posted by 36 sedan

Ferrite beads are what we call "Gremlin Catchers", they're used on most electronics now days, you'll often see one on the power cord and other cables on your computer (the bulge in the cord). Basically they trap and store unwanted frequencies (A/C).

Most likely at the higher speeds the fans are forced to turn faster than their motor will allow (sometimes referred to as the generator effect), this can cause the brushes to arc on the commutator producing A/C frequencies that can interfere with sensitive equipment.

The ferrite bead, either applied to the sensitive equipment (speedo) or the the source equipment (fans) will absorb the phantom frequencies and store them until the equipment is turn off. Ferrite beads are usually applied to one (sometimes both) wire of the equipment, usually the wire goes through a hole in the bead (bead slips over the wire’s insulation), the bead does not physically contact the wire electrically (leave the insulation on the wire), rather it works by inductance.

Ferrite beads come in all sizes, you’ll find them online. Check with your speedo manufacture for a size (frequency range) they recommend. Slip the bead over the wire tape it in place and it’s done.

One of my "tasks" over this coming winter is to replace existing gauges with a new set from Classic.. Thanks for the info on the beads!