I am fairly new to the trade and have never worked on one of these before. I got a service call that the condenser fan was not working. I replaced the fan motor and also the capacitor. When I test ran the unit in heating mode, everything worked properly. When I switched it to cooling mode is when I had problems. The compresser and indoor fan work fine but the condenser fan does not come on causing the compresser to shut off on high head pressure. This unit is old and there is no wiring diagram to go off of. Anybody have any ideas what could be causing this? Thanks!