I have just plated my seeds into a heated propagator with a lid. Condensation forms on the lid. (I over watered) I keep wiping away the condensation, but it keeps coming back. What can I do to keep the condensation away? Should I open the vents?
Yes. Especially on a day like tomorrow when the ambient air is very cold so it will be dry (low humidity). That will help to disperse the water vapour. Then close or partially close the vents again when the excess water has evaporated to stop the soil drying out too rapidly. Ideally you want to try to maintain reasonably good air circulation all the time to reduce the risk of fungus, mould and 'damping off'.