what causes an 01 to tick after replacing ol sending unit? on 2000 Mercury Villager

I replaced the oil sending unit & the ticking stopped but now it is doing it again is it possible that the part i bought has a manufactured defect or is there something else that needs to be replaced i am so tired of spending money and it NEVER fixes the problem PLEASE HELP!!!

Asked by for the 2000 Mercury Villager
Test oil pressure with a gauge. Is the 'ticking' more noticable after engine reaches operating temp.? What SPECIFIC conditions make it better or worse? How many miles on engine?
2 more answers
If it has adjustable rocker arms one could be loose or you could have a bad lifter take the rocker cover off and start the engine and check where the noise is coming from
how loud is the ticking