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I know this is going to sound kinda stupid, but during this time in the chilly north east corner ( Jax to be exact) its been getting rather cold. I Love my 2000 Neon to death, but the damn car never seems to heat up for me in the mornings, go out start car, flip the temp control over to heat, go back in side pack my lunch, get dressed (normally takes 15-20mins) and when get into the car to leave, its barely warm inside with the heat cranking !!! WTF GIVES ?!!

also when i switch to defrost, or any setting for that matter other than RIGHT IN YOUR FACE (all the way to the left) air just gets cold again, and doesn't heat up. I do have all the FSM's for a 2000 Plymouth Neon, but couldn't find my issue in them, unless I didn't look hard enough. BTW when you do turn the selector knob all the way to defrost, does the knob turn "all the way to the right" ? mine will go all but the last one, if i force it it just rolls back one "click",

-Mike

the same problem happend to my sisters jeep and i just put a quart of anti freeze and its good now

anti-freeze is good to go, hell all the fluids are new and topped off, and theres no oil leaks !! ( I know hard to imagine lol !!!)

-Mike

Thermostat, I had a similar issue with mine. And how cold we talking? I was just out driving and its 12 degrees out.

thank God not that cold, low 30's, but even in the hottest of days she never over heats, but I'm talking about the heat coming from the vents, when the heat is switched on, barely blows warm air,

-Mike

yea, replacing my thermostat fixed it for me. I barely had heat. So I did a coolant flush and replaced my thermostat , all is good now.

It does indeed sound like a thermostat.

For the record, turning your "heater" on doesn't have anything to do with what temperature air comes out of the vents. The air is heated by the engine coolant via a heater core in the dash. All you're doing is turning on the blower motor, and blowing it past the (cold) heater core. Until the engine is warm, you will not get warm air from the vents. The same goes for just about every car in the history of the world that has a heater.

Thermostat, or poor coolant flow through the core. If the A/C works, then that is why it gets colder with the defrost. The A/C compressor cycles in defrost mode.

The air blend door inside the HVAC box may not be functioning either. It basically moves to either close off the air flow through the heater core, or open it to allow heat through. The A/C evaporator always gets air flow. (the air flows through it first). The possible causes of blend door failure are the linkage has come loose, or the vacuum motor (if vacuum actuated) has no vacuum to it or is bad. This was common in the Cherokees for the linkage to fall off. But I don't think it is an issue with neons so much. The possibility is there tho.

A thermostat is fairly easy to diagnose. Just start the engine and feel the upper radiator hose. It should stay cold for a good while, then get hot quickly. If it starts slowly warming up a minute or two after start up, the t'stat is bad.

I'll have to check the t-stat in the am. I thought it might be a blend door issue, I did switch it from recirculate to out side and back and it worked everytime (ie recirculate/no blower=no air from vents, outside/no blower= air from vents) already checked the FSM this won't be fun to tear apart IF i have to replace the heater core.

Not to be a dick OB, I know how a heater core functions, not a hard concept to grasp, thanks to all for the imput, gonna tinker in the morning

-Mike

The air blend door has nothing to do with the recirculate door. Just an FYI. If you have a DCX FSM, it should illustrate the air blend door location.
But I'm betting on a t'stat., then heater core, or check the rubber hoses that go into the fire wall. If someone replaced them and they are too long, they can kink.

well it seems that what ever was wrong fixed itself, heater is working like a champ now

That doesn't happen very often ha ha consider yourself lucky! Most things never fix themselves

yea very true, hope it was just a sticking blend door, that unstuck itself lol

-Mike