Bf falcon single thermo not coming on

[Freddydecyka]

07 bf falcon xr6 with single thermo will not come on unless I switch ac on to pull air thru condenser. Replaced the thermister on the thermo with 3 others and still nothing, brought a whole new fan assembly with new thermister and still nothing. Checked all fuse and swapped relays around like 20 times with all different ones and still nothing. I’m at a loss as to why it won’t come and if anyone could shed some light or help me out, I would appreciate it. 
cheers lads