Auto relays are available with either resistor or diode circuit protection on the switch circuit. I believe it is to prevent voltage spikes from damaging circuit components when the relay coil is de-energised. What is the advantage of one type over the other?
A comprehensive explanation at this site. http://www.cbxelectronics.com/pdf/app-notes/app-note1.pdf
Wow! Cavemen like me shouldn't try to read stuff like that. All I need to know about that subject is if the diode or resister isn't there, I'll have problems in short order.
Are there "sensitive" electronics on the unit that could be harmed? If not, don't worry about it. Alex.
chroniekon, thanks for the link! Very good stuff.
If a relay without protection is switching an inductive load like a solenoid coil the voltage spike will quickly destroy the relay contacts. For you old guys like me it's like having a condenser go bad and burning up the points in your ignition.