1995 Mercury Grand Marquis windshield wiper and blower motor just stop working at same time. I have checked all the fuses. What can I do.
As with all things, correlation doesn't necessarily imply causation. Though in this instance it seems to be the case. Looking at a wiring diagram the two components don't share a power source unless you go higher up the tree. But then you'd have more than two components failing. Maybe they were and went unnoticed. They do share a ground however, G200 in the right kick panel.
Since both components are inoperative and sometimes come back to life on their own. You can infer (Knowing that they share a ground.) that the ground point is likely the source of your troubles. The easiest way to check the ground would be to perform a visual inspection. Luckily you need only to remove the right kick panel to access it. If you tested for ground at the wiper module or at the blower motor resistor. You would probably find that you had a partial ground or open circuit.
Welcome to the site. This sounds like you have an electrical short somewhere.
According to the owner's manual, those two circuits use separate fuses. So, it is not likely going to be a fuse issue.
You are going to have to trace wires and find where it is damaged. Unfortunately, there isn't enough information here for us to be able to give you a definitive answer.