Ruud heat pump blower and heat problem

I have a 20 year old unit i have been looking at. It is a ruud packaged heat pump. It hasn't been heating right. The first time I messed with it I set the thermostat to heat and auto for the fan and it went straight to emergency heat. Well I shut it off and messed with a few days later when I could get to it. I set the thermostat to heat;you could hear a clicking sound at the unit and where you take the filter out. The blower works fine on AC mode but when it is in heating mode the fan comes on the ON position and does not come on AUTO. what could be my problem to these two scenarios? Thanks

i forget to mention that it doesn't do anything now when i set the thermostat to heat but the blower works in AC mode

"Clicking sound" perhaps equals broken relay ?