Have you ever seen/used a diode like this with a relay ?

Air on board .com switch install diagram shows their switch in SERIES with a diode to prevent back emf.
I have never seen this done before, normally diode is across relay in parallel, properly polarity observed.

Whats weird in addition is they say if you are using it in a compressor, fridge or non lighting app to use diagram 1 which doesn't even show a diode ! Not that it matters anyway what you are switching, its the coil side that matters.

Does anyone here use diodes in any large relay to begin with to protect today's electronics ?
I know with all the modern electronics its probably a safe thing to do, but who does ?

They also might suggest (last line) a qualified auto "electricion"

 

According to your wiring diagram, it’s not for back emf protection, it’s to block current flow in the reverse direction when you switch off the ground path to pin 85 on the relay. Without it the relay could stay energized.

 

Yes it’s called a flyback diode, but they’ve wired it wrong. But a resistor across the coil is a better option.

 

I believe DRM is correct, were it to quell the reverse spike generated by the collapse of the relay coil's magnetic field it would be wired across the coil--as @mutely stated a resistor would be a better option for this purpose.

NTE uses a 680 Ω internal resistor to shunt the coil in it's 12 V DIN automotive relays:

 

Not following that at all.
When the switch is open the circuit is open, thus no current flow possible.
So how does the relay stay energized without the diode and switch open ?
Pin 85 needs +12 in the bottom figure to energize, not ground anyway.

 

The diagrams as depicted are incomplete, we know nothing of the switch's internals--I suspect the switch may have an ON indicator tied to the green wire and the switch's ground reference that could provide a ground path for the coil, through the indicator lamp, or some other potential (no pun intended) ground path when wired so as to switch the negative leg of the relay coil...

 

You are 100% correct. I have similar switch, and by probing concluded that green wire has an led to black (ground) for upper part of switch illumination, and blue had an led to black for lower illumination.

 

I see your point. I have never used these now I see the two separate led lights.
One for dash lights, one when on.
So they are not worried about back emf.