Quote:
Originally Posted by Speedfreak95
What’s the difference between the f/r and reverse contactor
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The main difference is the way the internal contacts make and break, or turn on and off. Electrically, they both do the same thing. Both are break before make switches.
Mechanically, an FNR rotates four studs with two bus bars 90°, to break then make.
A reversing contactor uses the same type of connection as your solenoid, namely it pushes the contacts together to make, then allows a strong spring to break the connection.
Both are prone to arcing if switched under load - which you shouldn't do - but the FNR adds friction to a soft material, so over time, the contacts wear, which causes resistance, which causes heat. A fairly common failure mode is for one or more studs - contacts - to heat up enough to soften the stationary part which holds the studs. Once softened, the studs become looser, which causes more heat, which soon results in failure to make contact.