1987 Chevy 1500 Truck

[s4orsythe]

I have a 1987 Chevy 1500 Truck and when I turn the heater on there is only cold air that blows out even when it's on Warm setting. I checked the radiator and it's filled to top. what could the problem be? Thanks.

[dolluper]

diverter valve on heater core [hose] going from waterpump to firewall vaccum line off or valve sticking

[84fiero123]

also posible heater core is pluged when the truck is running do both hoses feel hot if so cores good and diverter valve is working