Quote:
Originally Posted by Dr J
A point of clarification. The flyback diode is not there for the relay coil; it is for whatever inductive load the relay is powering. Thus, a flyback diode is definitely recommended even with SS relays.
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I am not sure you are correct there. If you look at the wiring diagram, the diode is connected across the primary coil of the relay not the contact side. I think therefore as others have said, it is there in order to short out the collapsing reverse surge current from the collapsing magnetic field of the primary. I have a high current diode from the car side of the battery master switch to earth, in case a rally marshal switches it off after an accident, without switching off the ignition first, to isolate the alternator and so that the master switch will also stop the engine. Again any reverse voltage from the alternator could in theory, damage various solid state devices like the DEM, noise reduction intercom and the digital rally navigation equipment.
Wilson