Toyota Repair Problems? Ask a Mechanic for Answers ASAP
Does the blower work on all speeds and there is air in the other vents and floor mode?
When selecting the other positions do you feel any binding in the mode dial and can you hear the mode door moving and stopping in the defrost position? On the left side of the A/C box can you see full movement on the selector mechanism that controls the modes when the selector is turned?
If you look up under the left side of the instrument panel just above the accelerator pedal and to the right you will see the side of the heater box. There is a control mechanism or lever system that attaches to the cable that goes to the mode select knob. As you move the mode selector make sure this mechanism is fully operating with no binding or restriction. Based on the description that you're giving me it sounds like that it is turning and going to the complete defrost mode because if you turn it fast you hear the thud. If you're still getting restricted airflow or lower airflow close both side vents for the driver and passenger dashboard vents these are not controlled by the mode selector. This will force all of the air onto the defroster. If it still seems to be not enough flow then there could be a problem with the doors or something inside the box itself but that would be extremely unlikely.
Can you look through the windshield and down into the defroster vents with a flash light to see if there's any obstructions in the vents themselves?
This only means some type of obstruction or the door mechanism is moving fully even though you hearing the outside mechanism not the actual diverter door inside.
Unfortunately yes I would probably start with pulling the radio and upper vent assemblies to get a good look inside the dash to see if anything looks unusual.
Just make sure that is the maximum position on the control lever and the side of the box is fully to the defrost mode and try to move it slightly more is there any unusual play there? Is it fully to the defrost position on the mechanism and the cable is fully in the defrost mode it has to be something internally.
Make sure it is not out of adjustment. There is a wedge/clip deal that can pop off to adjust the outer cable to move the lever assembly to the max position,
I was trying to make sure that you understood fully that the cable snaps into that metal clip on the side of the box. As you move the lever the inner steel portion of the cable pushes the mechanism in and out. If that's not adjusted properly the defrost mode can quit working. If you disconnect the cable from the side of the box by pulling it out of that metal clip then take the cable off of the mechanism itself can you manually rotate the mechanism fully with or without the cable then adjusted accordingly.
Our last two replies must of crossed I just saw that you put the two pictures up. That is basically the illustration that I sent you. If that mechanism is moving on all different settings and going completely to the full extreme on defrost and you still have no airflow something has to be disconnected inside the box. To be honest with you I've never seen this happen before these heater boxes are pretty bulletproof. The defroster vents come up out of the top of the heater box behind the radio there's no way to tell if there's anything inside their without cutting them open. In order to get those off the heater box and look at the defroster vents themselves the entire dashboard has to come out.
If you are 100% certain that the adjustment on the lever on the side of the box is normal and correct this only leaves something on the inside of the box not moving correctly causing the air to divert or not go to the defroster. If the blower is pushing the air through all of the other modes to the floor and vents unfortunately yes it's in the box and unless you are willing to remove the instrument panel then remove the entire box which is about an eight hour job you will have to live with it or pay a shop and that could run a size $1500 when it's all said and done.
When in the defrost mode there should be no air coming out of the center vents it will come out the side vents if those are left open. When you shift to the floor mode it should only come out the floor vents. What part of Ohio are you in?
This means the door is not moving inside the box if the outside exterior mechanism is moving when turning the knob for the mode select. If you want to shoot a short video clip of that mechanism while having someone turn the mode select I might build to see something going on that you not catching. You would have to post a video clip to a third party server than post a link here. I have to step out for a couple of hours I will be back on this evening. Dublin is nice ;)