2001 LT With "Confused" Heater & AC

A few months ago, a straw got sucked up into the front blower fan (heat / ac / defrost etc) the thing sounded like a freekin' helicopter! Took it in, had it fixed, and yelled at the kids for putting straws in the glove compartment. EVERYTHING WORKED FINE!

Now, months later - it got cold here in the northeast and the heater started to get a work out. We normally leave the thing set at 75 andn let the automatic temp control do the trick. But my wife and I noticed ... MAN ... it's COLD. SO i began twiddling the knobs of the heater control. NO matter what ... auto / front / defrost / max fan min fan etc .... it would blow hot then the flow of air would increase then blow "cool" ... then hot ... and then cool ... constantly. Again, this happens with AC button on / off ... recirc / outside air in. No matter what .. it pulsed hot / cold / hot / cold.

HERE IS WHERE IT GOT INTERESTING ....

When I put the TEMP control all the way to MAX COLD ... the vent's started belching HOT AIR CONSTANTLY !!! (auto / max fan / min fan ... whatever) ... I slowly moved the tmp control up ... a few degrees at a time. Still HOT! Then hit the ... about 74 degree mark and the old "hot / cold pulsing hit again".

ANY IDEAS AS TO WHAT THIS COULD BE ?

I have some ... lemme know what you think:

(1) The FIRST cold day, I started her up, and put the heat to MAX (it was COLLD) ... I heard a "THUNK" in the dash near the glovebox ... I've heard that before that's when this stuff started

(2) My FATHER in law in another car had a similar thing and if my assumptions are correct based on #1 above ....

COULD IT BE that there is some "air handling" flap that is stuck? Being part of the vent / fan system ... and having it worked on before ... is it possible that this could be the cause of the mixed up air. WE GET HEAT!!!! So I don't think its the radiator or heating system itself per se.

AND if it a mechanical air handler ... how much work would it take to fix it (aka ... do I want to attempt ripping out the dash to fix or pay the bill post warantee?)

ANY THOUGHTS OR SUGGESTIONS ???????

THANKS !

Bob

I have the same problem with a 2001. I have taken the truck to the dealer several times and they cannot locate a problem. They want me to bring the truck to the dealer when the problem happens. It stops after I cut the truck off and turn it on again. I am taking the truck to the dealer one more time and will let you know what happens.