2000 Dodge Caravan V6 3 liter
The A/C belt rotates fine on the pulleys until the air condiitoning system is engaged.
Once the air conditioner is engaged the belt smokes and then brakes.
Is this the compressor seizing up or could it be a simple relay.
Also, Where are the A/C relays for a 2000 Dodge Caravan? (any Diagrams would help)

 

I'll answer part of the question. What you describe indicates the A/C compressor is seized up. Sometimes the clutch bearing fails but then it will be locked all the time. No need to worry about relays at this point since it is a mechanical issue. Depending on why it seized up, you may have shavings and dirt in the refrigerant loop which means you need to replace the compressor, flush the system and install a new reciever/drier. Bad news--this will cost you about $200 if you do it yourself with a reman or used compressor.