I have a 1995 F150 step side that has a viscous fan on it which I replaced. If I am standing still and my a/c is on it will blow warm then get moving it is cold and I can hear the fan on then will kick out. What causes the a/c to stop blowing col, could it be head pressure? TIA

 

That's about 5 questions rolled into a few run-on sentences...

Why exactly did you replace the fan clutch? Did the replacement pass the same test that the previous clutch failed? Click this & read the caption:


(phone app link)

Have the refrigerant evacuated & recharged by a pro, to make sure it has the correct amount: 2 lbs 6 oz (38oz) of R-134a. The label on the truck may say different, but that's the updated charge, according to Ford's TSB 94-19-20. An evac/rech. won't show this, and it only matters if the entire system is replaced, but it takes 11oz of PAG-46 (also revised in a TSB). Write them on the truck in paint-pen so no one has to look them up.

If the fan actually stops, inspect the fuse in the dash:


(phone app link)

But it's more likely that it's just switching to the defrost registers, due to a vacuum leak near the Right hood hinge:


(phone app link)

 

The reason i replaced the fan was due to I replaced the water pump and since fan was off I thought I would go ahead and replace. I can hear the fan engage when I take off at a light or a period of time sitting. The a/c charge was a thought also as it does not do this all the time.and varies on how hot it is outside. I will check and see thank for the input.

 

By that logic, you should replace the entire truck, because you replaced the water pump. No - replace ONLY those parts that are due on the maintenance schedule, and those that fail a published test.