The heater and defroster does not work on my truck. Neither does the air conditioner. Can I by pass the in line valve on the hose to the heater core to eliminate that possibility and get use from it with out hindering the functionality of the system? I know of other toubleshooting points such as coolant, blend door, door accentuator, clogged or rusted heater core, water pump, etc., etc.. I'm low on funds so I'm trying to do this on my own. Any help would be appreciated. Thanx