I did some testing to see if I could get radiators to work with an active microwave receiver on board. I started with a fresh install of KSP and only installed Interstellar. I put one of each type of radiator on my test ship and none of the radiators dissipate waste heat when I have a microwave beamed power receiver active. I did find a work around though. If I retract the heat radiator, it starts working. If I extend it, it stops working again.