Nissan sentra 1998 air conditioner problem

That's a tricky one. Sounds as though there may be a loose connection / dodgy fuse or even a charging fault. I assume the battery lamp is not glowing at all when the engine is running.

Make sure you have proper water to antifreeze ratio. Not just straight water or anti freeze. Make sure the thermostat is in good working order.. A good tip depending on where you live and how hot it is outside. Any time you start to overheat. Roll down the windows and turn the heater on full blast on the hottest setting. Make sure radiator is full and overflow bottle has antifreeze too. Because when the thermostat first opens the system has a suction and will draw from overflow bottle

Worn out battery--check that out

Did you not check for codes yet?

This is due to the fact that the solenoid relay is stuck and so the ac is not cutting off. You need to open the hood and check after starting the car. If the fan is cut , does the ac cut off, if not the relay or the solenoid of the compressor must be checked.

Blower motor only works on high speed

have you cheeked the ignition (coil ) ?? probably it is
because we learnt it (the coil) comes down after engine high temperatures
yes i know if car cools down and turn on again it is surely bad coil
but some times the coil is just dead not only bad

Sounds like a broken wire

There is Blower Motor Resistor located at the passenger side, right side at the feet. Mounted by 2 screws. You should be able to see electrical connector going to it. Replaces in minutes.

good day, try to check the compressor maybe thats the problem. i hope this tip will help you.

I had the same problem with my 96 Nissan/ infinity g20.
If I turned on the ac the brake & battery lights came on, the AC fan would work but the air did not blow cold. Disconnected the battery for a few hours to reset the computer. That solved the problem.
Now, no lights, and the AC blows cold.