Okay so my 96 1500 has no heat what so ever. From what all I read, I squeezed the lines goin into the heater core earlier and they were warm but I'm pretty sure it was just engine heat cause there soft like there's no pressure in there and it was just warm not hot. Pretty sure the selector controls good cause my ac works and I doubt it's the blend door cause just cold air comes through even when I'm driving. Do you guys think there's a blockage or would it be some other control issue not bringing it on with the lines soft like I said?

 

How long since you last successfully used heat?
My blend door was stuck to the foam seal, as it had been in the one position for many years.

 

i've only had it since summer so i never ran the heat myself

 

Over a period of a few days, I cycled hot/cold on the switch several times... eventually, it let go and worked.
I did however get showered in foam crumbs as the rest of the seal disintegrated and blew through the vents.

 

If the hoses are not hot the blend door will not fix that, the hoses have to be hot, if your temperature of your engine is driving pretty cool, you could have a bad thermostat, I recently put one in for a friend bought at Napa, after about a month he told me his heater wasnt working good at all, when I took the thermostat back off ,the center had popped off and it had no control over the temperature, it ran cool all the time.

 

its also possible to be a little low on coolant and have an air lock in the heater core.

or - the heater core could be stopped up with crap, preventing flow.

try disconnecting both heater hoses at the engine and backflushing the heater both ways. when finished, leave the lines full of water. i prefer to cut the heater hoses in a convenient place about the middle of the engine and use a couple of 3/4 inch dorman splices and clamps. its just easier that fighting with the clamps on the manifold. i also don't like to try to disconnect the hoses at the core. its too fragile and the core is too hard to get to (remove dash) to risk breaking a pipe.

 

Yes the heater core could be stopped up, And if you have to change the heater core out, I have a lot easier way...first time less than 30 minutes. PM me ,if enough want it I will post a how to. I have changed out about 20 of them for friends.

 

^ everybody wants to know.

 

^^^
Yes, everyone WOULD like to know... please do share!!! I'm going through the same issue myself, if I have to change out this heater core in a week, I'd like to know how to do it simply like you said!

 

Pretty sure I have air locked in mine, the heater lines are hot to the touch but I get the same cold air issue many talk about, only warm on low fan speed, and just warm not hot. Plus it was below the add line on coolant when I bought it last week and I hear gurgling when I rev the motor slightly and get that water pump spinnin. So I'm planning on doing your easy backflush method dhvaughan, great tip!
Yeah, I picked up a 98 with 150k on it last week when it was 60 outside, then two days ago the temp dropped to the teens at night and it snowed, I then realized I had no heat, awesome