Why do I have low hot water pressure, cold water pressure is fine. The faucet screens are not plugged.

If you have the older galvanized (metal) pipes, they could be full of rust and other build up. If this is the case, replace the plumbing with cpvc.

Why do I have low hot water pressure, cold water pressure is fine. The faucet screens are not plugged.

Is it all over the house or just one room or fixture? Like mowerman asked... what kind of pipes do you have for your water? Could also be a problem with the hotwater heater.. though that is rare it does happen... can you give us a little more info.