start with the basics, is everything there? heater core, heater hoses, tap/valve etc
assuming it is, when you slide the cold/hot lever from cold to hot, does the heater tap open? if not, reconnect lever or just move heater tap by hand
is it a fan issue? check fan speed resistor or power to blower motor.
need more info other than its cold, fucken oath its cold LOL![]()