I have a 12VDC relay to control my music system in V8, but when I turn off I always have a violent "plopp"!!
Now it came to my mind that when the control voltage is switched off, an induction voltage is created in the case of DC relays, and this hits into the power supply from the car!
( test without relays: everything ok!!)
Is it enough to switch a diode between + and - from the relay coil?
Or is there a circuit with an additional C or R necessary?