72 C-20 Heat in cab

[saddletramp]

Afternoon Guys can i get some help the PO of my truck tore the heater box of the fire wall ive put it back with a new heater core its a AC truck i just want heat for the winter months what do i need to hook up for heat only also the water hose off the water pump does that go on the bigger connection to the heater core ? Thanks Appreciate you guys

[72LB]

There are two sizes of hose that go to the heater, 5/8 in on the top and 3/4 out at the bottom.

[geezer#99]

Easy way to remember is out of intake to bottom of heater core, out of core top back to water pump. Some set ups have hose go to rad instead of water pump.

[sick472]

You'll need the fan to be functional. Does it work?

It would also be good if you can switch from the floor heat to defrost too.

[saddletramp]

Thanks for the help Fan does work i cleaned up the heater box that goes on the firewall i got the flapper working thats in that box so is that all i need ?

[sick472]

Hoses hooked up and hot coolant going to the heater core...check.

Blower fan working...check.

You should have heat with just the above two items, but where will it be coming out in the truck???

There are at least two, maybe three flappers involved. One or two in item #12 and one in the light grey box above item #15. IIRC, one flapper in the AC box at the firewall controls AC air or Hot air while the second diverts air to the dash vents OR down to the lower box. The one in the lower box changes floor heat to defrost.

You don't need these flappers to be functional to warm up the cab so long as you don't care where the heat comes from.

[saddletramp]

Thank you ill post what i found when i get it going