relay replacing wire with thin one

I have a Bmw e36,1994 and my sunroof stopped working when i pressed the switch nothing happens.I discovered the cause it was a relay located under dash a SPST relay.terminal 30= 12+volt alltime 5mm diameter wire,terminal 87= to sunroof switch 2mm diameter wire,coil-terminal 85 =12+volt 5mm diameter,terminal 86= ground, a thin wire from ZKE(-central unit of car).The fault-the ground was dead from ZKE no output to terminal 86 to close relay.Since i did not found the fault,and no ground switched trough ignition(i want sunroof to work only with ignition on),i cut 85,86 terminal wires and i put terminal 86 to ground alltime,and 85terminal to a 12+ switched trough ignitio.I used for 85 terminal a 12+ v signal from accesory a thin wire about 1mm diameter.  Is that a problem,because as i mentionedthe original 85terminal had a 12+v wire wich was about 5mm diameter?COuld i burn something like accesory wire?Why the wire was 5mm it needs more curent draw?

as long as you have left term 30 the same you will have no problem or burn anything because you are using term 86 and 85 with the smaller gauge wires to just activate the relay, correct? if so, no worries. a relay coil only draws 500ma of current.

Yes but why was the 85 so large in diameter about 4-5mm?

Maybe you misread the terminal designations, swapping 87 and 85. usually the two thick wires should be the current carrying wires, and the thin ones control the relay.