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Air vents only blowing at windshield

nweb992000

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#1
I replaced the HVAC actuator in November to fix the clicking noise they make when they go bad. It fixed the noise, but now it's heating up in Texas and I noticed that air only blows at the windshield. It was working before I replaced it. I thought that it blends warm and cold air, not directs it. What gives....any thoughts?
 

Handy Andy

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#2
As I am finding -

This requires some disassembly of the front dash and console all over again but look for and see if the actuator motor is able to move the "drum" within it.

The drum itself sits inside the air assembly, with the blower motor in a cage in the middle of it - the drum moves - rotates - and has a set of precut slots or holes - when you turn the climate control settings, air from the blower motor fresh from the Air intake control dam (Fresh outside or Recirculated inside) gets centrifuged to the space in the drum. The actuator which is located on the driver's side just above the throttle pedal - between the radio, the dash pods and the pedal, moves the drum to roate these ports for the vent system - aligning it's slots or holes to the holes or ports in the outer assembly that holds the drum blower inside - and the vents to the outside - to the passenger compartment. The drum simply moves, the holes either line up and you feel air commnig out, or they continue their travel using the actuator gearbox to align to another set of holes.

1648999306496.png

The Actuator is similar to the air-door actuator - and if the actuator was accidentally reseated in the wrong position and then a reset - you have to remove it, rotate the console controls thru their steps, and watching the actuator gear rotate as well, the direction of rotation, the length of time it does this, and where it stops in aspect of the climate control setting - you have to find its "home" then by physically moving the gear it rests and rides along with - find it's extreme stops and also feel the air blowing out of particular vents for a particular setting and then install the actuator before it forgets - so this has to be done with the engine running or at least in the ignition on and a battery charger to keep the system alive.

You may also have an issue of the drum getting stuck in a position
  • - you'll hear a grinding or thonk thunk tonk - while it tries to move
  • - means that the drum is jammed in a position by some object - pen, pencil paper clip small change - petrified French fries - jamming the drum in that position.
  • Something may have gotten in from the outside, got into the vent and migrated down to the drum - jamming the hole and preventing the drum from moving.
What is unique about this system, is the actuators - they use limit sensors inside their gearbox which is basically a stepper motor, a set of gears and the limit travel sensors that let the stepper move only so far - once that limit it reached - it's stopped by losing electrical contact of a wiper across a resistive element. IN doing so, the system can the reverse direction and the stepper - being a simple DC motor - simply turns again, only in the opposite direction.

1684633792613.png

So the system uses a series of "timer" settings to make the actuator run for a preset amount of time - it has power to do this by you setting the control to a icon, the system then runs the actuator for a given amount of time that lets the drum turn only so far to a position. If the drum gets stuck in a position - the time runs out so it doesn't burn up the motor trying to force it. It simply stops. Turning the system to "O" is considered home, so it then reverses the motor and again a timer runs to help it find home. In wiring of the unit - some have 4 wire while others have only 3 - the 4 wire ones help the system reset itself to "O" anytime a system reset is done by the BCM as part of a self test. In a 3 wire system - it's uses the wiper contact as a follower - to help it find a location and sometimes can "remember" a position if you turn the system off when the engine and system is off - so it holds in that setting - then when you move from "O" to a new setting - the thing remembers where it is, then moves until the wiper arm wire senses it's found that other setting - again using a timer. So if it takes too long - it simply quits moving sometimes in between positions and all you hear is a roar of the blower but hardly feel any air moving.

To help you, "O" is at one of the extreme rotations of the drum, rotate with your finger - that gear until it stops rotating, with the blower on full, one extreme - all vents are closed, then Floor, DEF Floor, DEF, Dash, Dash/Floor then MAX A/C which is at the other extreme of the rotation.
 
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nweb992000

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Thread Starter #3
Thank you, extremely helpful. I'll take it and try again. I'll let you know how it turns out.
 

Handy Andy

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#4
The only "bear" I had with the actuator - is in taking it off.

Uses torx screws and uses three - might want to remove the lower (below steering column) kick panel to let you have better access to the driver's side actuator. Just remember to lift and pop off the Air bag connector else you'll need resistors to "numb" the SRS until that can be fixed.

The wires to it - they use a snap-in insert, to keep the connector from dislodging - it's a lot like the Air Actuator one in the Intake Fresh/Recirculated. And uses similar sized torx bit for the screws (#15 I think) The Air is Red, the drum one is white or lite yellow - just lift the tabs to allow the press-in tab to release the connector.

That is if you just want to set it and forget it - for example, the MAX A/C setting versus the floor vent / top defroster. I've done that before, just move the gearbox to find a comfortable setting for air to flow out of the vents, to buy me time to figure out the mess that occured and then put it / align it - together right so I can enjoy "Climate control" again. But if needed or you just don't want to fuss more and save this for another day, just rotate the gearbox and let the air forced out in the blower let you find which set of vents to use for best results in summer and then just rotate gearbox for winter and then you don't have to mess with the actuator, period.
 
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nweb992000

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Thread Starter #5
Don't mess with the actuator...I'm almost at that point. When I rotate the gearbox to what seems right, the actuator won't line up. The gear in the actuator will not turn, it is frozen in position. Is that correct, or should it turn?
If I leave it out, what do I lose?
 

Handy Andy

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#6
As said earlier, I set it to a comfortable enough setting to at least blow air out of some ports, then got an actuator from a junkyard and verified that it was working (compatible) by just connecting it and watching the gear turn - I originally set it to "O" then to DEF - and since the blower was going - rotated the drum gear to match the airflow from the top defroster vent.

You have to wait to make sure it knows - you can watch the gear turn then stop - and even move back slightly - its "homing" a position it thinks it should be - that is normal and you have to await for the gear to stop - then install the actuator - while the power is on - seating the gear to mesh with the Drum gear - you should NOT have to turn it (actuator) by any real degree to make the holes line-up to screw it back together at all - then just install the screws and tighten. You should be ok.

I just used a setting to predict where the actuator gear turns a set number of rotations (by timed event) then turned the drum to meet that setting by air moving out that vent - then installed it - that is what I meant by memory - don't shut off the fan or engine else it may try to find "home on its own" - and you'll have to do this all over again.

When the connector is in, the actuator gear should turn the thing should rotate as you rotate the climate control knob.

But if it doesn't, or it's not - look around the fuseblocks for a blown fuse.
1649202694319.png
 
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nweb992000

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Thread Starter #7
I see. I'll try again tomorrow and let you know.
 
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nweb992000

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Thread Starter #8
As said earlier, I set it to a comfortable enough setting to at least blow air out of some ports, then got an actuator from a junkyard and verified that it was working (compatible) by just connecting it and watching the gear turn - I originally set it to "O" then to DEF - and since the blower was going - rotated the drum gear to match the airflow from the top defroster vent.

You have to wait to make sure it knows - you can watch the gear turn then stop - and even move back slightly - its "homing" a position it thinks it should be - that is normal and you have to await for the gear to stop - then install the actuator - while the power is on - seating the gear to mesh with the Drum gear - you should NOT have to turn it (actuator) by any real degree to make the holes line-up to screw it back together at all - then just install the screws and tighten. You should be ok.

I just used a setting to predict where the actuator gear turns a set number of rotations (by timed event) then turned the drum to meet that setting by air moving out that vent - then installed it - that is what I meant by memory - don't shut off the fan or engine else it may try to find "home on its own" - and you'll have to do this all over again.

When the connector is in, the actuator gear should turn the thing should rotate as you rotate the climate control knob.

But if it doesn't, or it's not - look around the fuseblocks for a blown fuse.
View attachment 6387
 
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nweb992000

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Thread Starter #9
So, here's where I am. The actuator is plugged in, but not mounted. The actuator turns when I start the engine. If I change settings it doesn't move. If I rotate the gear to match the actuator gear so I can install it, I'm back to square one with air only coming out of the windshield vent. What am I not doing?
 

Handy Andy

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#10
The Actuator turns when you start the engine - changing settings - nothing happens.

Replace the Actuator - more than likely the "stepper motor" cannot rotate in the opposite direction - they are supposed to rotate back to "Home" when you select "O" in the Climate control. So, the Gear turns but does not turn back tells me that is why it's stuck - the Drum gear has its own built in limit stop - so it doesn't just roll and rotate haphazardly so once the Actuator rolls the drum all the way to a limit stop - the gear won't let it go (rotate) back to home, that is why that is occurring.

Realize that you had to watch the actuator work and for you to try the controls to see if the gear would reverse - since it's not - the next step is replacing the actuator.
Since it doesn't roll backwards, there may be two issues,
  • The Actuators stepper motor is shot - only goes one direction
  • The LOGIC for the stepper motor system - the way it works, is bad, and needs replacement.
  • A third one can be the wiring is damaged but requires troubleshooting.
    • Did you see how many wires to the connector on the Actuator?
    • If only two - you have the Basic system - it reverses polarity in the connector back at the Climate control.
    • Three allow for reverse and follow
    • Four allows for stepper increment and back step - with follow and used for bi-level control
    • Let Me Rephrase this: The climate control head THAT uses a thermostat and temperature display to help - if that is the type you have, the logic control is bad for you won't be able to control or it (actuator to) follow user climate settings.
 
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nweb992000

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Thread Starter #11
I'll try another actuator. And get back. It's a two lead connection, and cost me about $20 on eBay.
 

Handy Andy

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#12
1649383448565.png
The above schematic may or may not help you in understanding how two wires can be made to reverse, but the idea here is to develop a way to reverse polarity without too much fuss in relay or toggles switches. Instead, they use MOSFET solid state to turn on one wire to "ground" and the other wire stays hot because the part the controls the other MOSFET on the opposite terminal is off so, power flows thru the terminal - letting the terminal remain at powered level thru the V+. while the other terminal is turned "On" and then sinks current - the V+ feed is sent thru a resistor to both sides (omitted to keep this simple) so they both don't blow up the part or force too much of the current thru the motor connected to these two leads.

So, when one part is LOGIC 1 - it turns on and ground appears so power flows from the other terminal thru the motor back into the MOSFET that is on, thru itself, to ground.

The turn that MOSFET off and turn the other one on - this completes the circuit again and the process occurs, but the polarity of it is reversed. The Motor turns in the other direction.

It's very simplistic but the concept shown, I hopes helps you understand how two wires can be made to make a motor run in reverse.
 
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Thread Starter #13
So, I put in a second actuator. This one does nothing when engine is on and settings are changed. Not likely anything is wrong with the actuators. It looks to me that it must need to be calibrated some how. So at this point, I'm out. I was thinking it was a straight up replacement. Clearly, that's not the case. Thank you for the input.
 


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