First post, this board is great. I got an 83 C20 4x2 with the 454 for my birthday from the original owner. It's not a looker and needs a little TLC but overall runs like a champ. Truck was used to pull a horse trailer for its life and sat outside. Mechanically they took care of it, but i think I was the first person to vacuum the interior in several years. ;)

The current mystery is the front heater. The blower works, but the heat never really gets hot. Oddly, if i switch to defroster the air coming out seems to be warmer, but its rarely, if ever hot. So i'm curious as to what might be causing it.

Background: So far I've replaced the thermostat (thought maybe it was stuck open), temp gauge (broken) and rear heater core (leak made a mess out of cargo area), and redone the headliner (just proud).

Info: when the rear heater was leaking, the coolant level was low, and so i figured that was probably it. now that that's fixed and the coolant level remains 'full' still the same problem. There's no (visible at least) coolant leak in the cab where the heater core is, but i haven't taken it apart to see as the coolant level stays good. The hoses going to from the heater core in the engine compartment are both hot. If i move the temp control from cold/hot, when its really cold out, it does get colder, so the damper seems to be working (at least some). And yes, I wait til the engine gets up to operating temperature (temp gauge pointing due north).

All that being said, given enough time, the heater will heat up the truck, but it feels more like a heat pump (warmer enough to get the cab up in the 60's or 70's over enough time) but is never 'hot' (or warm even) if you stick your hand in front of it. By comparison, with the new core in the rear, when the truck is hot, if you turn the fan on, it blows hot air and the core gets VERY warm to the touch. (of course that motor had a short in it so i'm not using that til i can find a replacement, but i digress)

Any ideas on what it might be and/or how to figure out what it might be?