You probably have a build-up of corrosion inside the faucet stem or a detriorated O-ring which is jamming the stem. Faucet parts are available online or from many marine or RV stores. Fixing it is similar to fixing a faucet at home. Before beginning, check with your local marine or RV supply stores as to whether they carry parts for that brand. If so, turn off your hot water heater and the pressure/pump to your water system. Depressurize the faucet line by turning on the hot water and letting it flow till it stops. Then remove the faucet stem and check for corrosion or a deteriorated rubber O-ring. Bring the faucet stem and any deteriorated parts with you to the parts store to match the parts. If you can find the model number of the faucet, that would definitely help. Hope this helps. Hy