Ford Repair: 1988 T-Bird, oil pressure switch, car beeps

Question
1988 T-Bird, 5.0 EFI. 80.000 miles. Changed dist. cap, rotor, air filter, water pump,and oil. Added STP oil add., and Marvel Mystery oil.  Passed Cal. Smog. After changing water pump, the car beeps when turned on. Oil gauge shows on LED dash, little   oil pot and H and L. What is wrong? Is it safe to drive?

Answer
is it rattling? there is no reason to have added stp to oil with that low of miles did you see how thick that stuff is? i only use it for extremely high mileage engine and them only to get someone by-marvel mystery oil on other hand i highly recommend every now and then to help keep lifters clean if suspect of an sludge around otherwise just good quality oil synthetic preferably like mobile one extended or amsoil 100% very good for engine-and pocketbook in long run.

if it is not rattling or ticking you may have knocked wire off of oil sending unit by oil filter or stp or sludge if you have any may have gotten in oil pressure switch-switch could have gone bad which is longshot-or you may have actually lost oil pressure if you hear any noise rattling,ticking,knocking do not drive the car have it towed to repuatable garage. good luck