1997 Nissan 4 cylinder truck AC works excellent throwing snowballs cold air, then it will blow hot air. Relay switch and clutch has been replaced....Did not fix problem!

you need to trace the cause of the fuse blowing, see an auto electrician, save you a load of time

Edited OP question for clarity.

Most likely cause is the A.C. clutch relay, which is the part that _actually_ turns the AC on. Details here.

https://www.google.com/search?q=2007+Nissan+Altima+AC+clutch+relay

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this could be a hole in an AC line trace or have the lines traced replace and replaced Freon

The likely cause is a bad compressor clutch, but there are other possible causes. The first thing to do is to observe the compressor with the engine running. The clutch is inside the pulley. When the a/c is off, the pulley turns on thr belt, but the clutch does not turn. When the a/c is turned on, the clutch should lock on the pulley and turn with it. Run this test and post the result here.

Someone will need to find out if the compressor clutch is failing, or if it is loosing power due to a pressure switch or other problem.
A faulty relay or switch could get hot and switch off power to the compressor.

Could be a list of things including low on freon, low pressure switch, relay, or the a/c clutch on the compressor.

My 2003 Toyota Camry AC often starts blowing hot air and the AC light starts blinking. I don't know why the following process works, but it does. Using the temp selector (left) reduce the temperature all the way down to Max Cold and then push the Auto button. It will start blowing out very cold air. After a little while push the temp selector to the desired temperature.

Sounds like the AC relay/switch is sticking on sometimes. Locate and swap this relay. Look at your fuse box lids for location or search online for the exact location. You also might have a leak in the ac lines or the AC condenser clutch is not engaging to kick the ac on. You should feel a slight power loss or hear a slight stutter in the engine when pressing your AC switch. This means everything kicked on. It's a millisecond before the ECU realizes this and kicks up the idle to compensate.

your air con needs re gasing

when an AC gets real hot and there is air in the system you get what is called High Head Pressure and the high pressure switch will not let the clutch engage. Need to have the system evacuated and recharged.