Blend door air mixer photos

[airline tech]

I found a much better diagram of the system; I had a co-worker look at this issue for a second opinion.
He agrees that the easiest option would be to tie in switch in the motor wiring, but the per the description the Recert button is disabled when (off) which means you will most likely lose power feed on those wires (pins 3 and 7)- The only way to find out is to break out fluke meter and do some on truck testing, as when off, do you still have power on those pins

I believe it is only momentary power, once door reaches its end point stop - power is dropped, so this is something to test with meter (as well)

If there is power, then you should still have end point (door travel) contact to drop power off when door fully closes, by installing a secondary switch to reverse the motor to drive inlet door closed.
Just don't know what it will do as far as feedback errors to the other sensors, as we don't know exactly what power is completely dropped off when (off)
If the other sensors are powered off, they won't see fault

To clarify: The end point is a contact point on the drive gear, when it reaches this end point it provides feedback to the FCIM to kill the power feed and stop the door movement

If you bring power in from another source, you will over drive it, no feedback to drop power, I have not messed with these actuators a lot in my career, but have changed a few, I do know they are very sensitive (weak) as they are only moving a small door, it does not take much to damage the gears (internally)

If the system was not so complex and tie in so many things into the feedback circuit, it would be a fairly easy modification

I am attaching an easier to follow diagram of the system, print it out and lay pages side by side

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[airline tech]

I did a quick check today with Fluke, Pin 3 and Pin 7 only have 12v DC power when the door is moving. Pin 3 =Powered when closing (Recirculation-On) Pin 7 = Powered when opening (Recirculation - Off)

 

[JDowns]

I haven't been up in there in awhile but I don't think the blend door when closed is a tight seal, in fact there is a good sized gap. The blend door just moves into a position where the "majority" of air is either pulled from the exterior or interior.

 

[airline tech]

I haven't been up in there in awhile but I don't think the blend door when closed is a tight seal, in fact there is a good sized gap. The blend door just moves into a position where the "majority" of air is either pulled from the exterior or interior.

I agree that is most likely is not an airtight seal, will have to use flashlight shining in from cowl towards door to check for sure, but looking into a way to mod with switch or relay to manually close door (Keep Recirculation) active vs cycling on its own for owners who live in wildfire areas, smoke inside the cab. For me personally it is a modification possibility to close door when truck is shut off vs defaults to open. This will only work if door fully closes block rodents (mice) from entering cab.
I plan on installing the screen to cover the cowl inlet frame cutouts for that, but since others are having health concerns over this door, it would be nice to find a solution to help, but negates the sole purpose of the inlet door and that's to keep fresh air flowing into the cab, hard to do when that air is also pulling in smoke, if a solution can be found to close the inlet door even though it's partially open it would at least slow down the intake. I don't live in a wildfire area but have noticed driving down country roads, the truck does inhale the skunk, exhaust and other funky smells quite easily, way worse than any vehicle I have ever driven, but it seems to dissipate quite quickly thanks to the exhaust vents behind the rear seat

 

[JDowns]

I agree that is most likely is not an airtight seal, will have to use flashlight shining in from cowl towards door to check for sure, but looking into a way to mod with switch or relay to manually close door (Keep Recirculation) active vs cycling on its own for owners who live in wildfire areas, smoke inside the cab. For me personally it is a modification possibility to close door when truck is shut off vs defaults to open. This will only work if door fully closes block rodents (mice) from entering cab.
I plan on installing the screen to cover the cowl inlet frame cutouts for that, but since others are having health concerns over this door, it would be nice to find a solution to help, but negates the sole purpose of the inlet door and that's to keep fresh air flowing into the cab, hard to do when that air is also pulling in smoke, if a solution can be found to close the inlet door even though it's partially open it would at least slow down the intake. I don't live in a wildfire area but have noticed driving down country roads, the truck does inhale the skunk, exhaust and other funky smells quite easily, way worse than any vehicle I have ever driven

look from the outside in with blend door closed. If I remember correctly the gap along the top edge is sizable enough where even a mouse would not have to squeeze through. All the blend door does is redirect where the majority of flow comes from, the gaps around the firewall and blend door are pretty significant.

 

[jblc]

Correct on the door not fully seating. I've read it's designed for 10/90 mixing (10% outside even when closed).
Unfortunately, at >35-40 mph, that 10% is enough bad air to completely overwhelm the truck's filtering (and an additional shoebox-sized HEPA filter i place to the back seat).

 

[airline tech]

Just a thought on this issue, Now granted I do not know how bad you smoke issue is, but I was thinking about something (an idea)
It comes down to is it the smoke itself or the pollutants it carries is the issue?

Option 1:
I was thinking, that if you make the interior cabin filter a secondary filter and install a filter in the cowl area (limited space) to actually build a housing for it but find something (filter) wise to cover the holes (flexible) and then tape down thus making it a primary filter
It would defiantly help but how much is the question

Option 2:
Completely cover the Holes above the Cabin Air Filter, as I believe those holes allow inducted air from cowl into the cab (unfiltered)
The only air that is filtered is the air that is drawn down into the blower motor, before it feeds the ductwork.
I plan to test my theory with shop air.
Using below pic as ref - that's daylight you are seeing through the holes, inlet door is open
I believe that this is the 10% air source

But: The only issue is I think this is the Recirculated Air (Inlet) source, but since it spends so little time in (Recert) it should have very little effect on system

Again, it's just me brainstorming for an alternate working solution

 

[jblc]

Thanks for the thought! But, I'd caution against sealing those holes (above the filter) in the cabin. Those are where the blower gets its air from, when in recirc mode. The blend door closes and leaves that mesh as the recirc input.

If that recirc input is sealed off, the blower will likely overload.

Using below pic as ref - that's daylight you are seeing through the holes, inlet door is open
I believe that this is the 10% air source

Agreed that's the outside intake. That's pretty much covered when in recirc mode. Last weekend I'd also looked more carefully at the blend door sealing, and I think it can be made to seal a bit better. It's actually not as bad as I thought, but at high speeds, even a little can lead to a large amount of pollutants coming in...

Relating to recirc turning off constantly and keeping the blend door closed, I still think the humidity sensor hack route is the most useful. I'll best taking apart the dash to find it (unless you've already found it), and test that out shortly.

 

[airline tech]

Thanks for the thought! But, I'd caution against sealing those holes (above the filter) in the cabin. Those are where the blower gets its air from, when in recirc mode. The blend door closes and leaves that mesh as the recirc input.

If that recirc input is sealed off, the blower will likely overload.


Agreed that's the outside intake. That's pretty much covered when in recirc mode. Last weekend I'd also looked more carefully at the blend door sealing, and I think it can be made to seal a bit better. It's actually not as bad as I thought, but at high speeds, even a little can lead to a large amount of pollutants coming in...

Relating to recirc turning off constantly and keeping the blend door closed, I still think the humidity sensor hack route is the most useful. I'll best taking apart the dash to find it (unless you've already found it), and test that out shortly.

I played with it a bit, put it in Recert and I could feel cold air mixing at the vent holes above the filter.
I placed a piece of paper against it (In Recert) it does draw some air, but it is minute.
I then wrapped towel around it as best I could, did not appear to affect blower motor.

Turned off Recert - no cold air felt at vent holes as all air now flowing down to blower motor, still need to place shop air or fan in front of the cowl vents, to see when in recert if any outside air is actually coming out of the vent holes by-passing the filter. (Need to simulate driving) air flow

See attached for the Humidity Sensor R&R

 

[jblc]

Thanks for the humidity sensor location I have the humidity sensor out.
Removal was more awkward than the document showed: the sensor slides BACKWARDS, so it needs to be fished out of some small holes in the dash.
Reinstalling could be challenging.

Notes:

(1)There was so much confusion (on other threads) about what the actual part is. Here's the part number written on it: G3GH-19T562-AA.

The surface-mount humidity sensor is right behind the thermistor:

(2) I took measurements of an operating sensor , while the vehicle was On, using probes that poke through the wire insulation. I have a range of output voltages depending on my breath (higher humidity). It's a reasonable-scale output, so we're not operating at the mV level here.

Based on my measurements, preliminarily, this seems straightforward to modify.
I'll need to make a connecting harness, so need to find the connector and socket.

I found a link for the female side; but no male side yet.
Turns out "1456985-1" (written on the side) is the correct part number for the female side. The texts on the front isn't as useful.

Can anyone help locate the corresponding receptacle? I'm unable to find it online...

(3) By the sensor diagram, pin 3 and 5 of the humidity sensor module seem to be +Vcc (unknown voltage) and Gnd. Gnd and voltage is 55-2 C and D in the schematic, but I can't tell where those go; I can't find the connection points in the other docs; let me know if someone sees it. Either way, measurement show it's +5 V.

(4) There are 2x humidity I/O to FCIM: pin 19 (Humidity Signal) and pin 27 (Humidity). But pin 27 seems to go to pin 1 of the motor -- which turns out to be a small intake fan on the unit. It's not clear: why is pin 27 labeled Humidity? Am I missing something? Either way, pin 4 seems to be the correct humidity output.

 

[jblc]

Update to my last post item(2). I spoke with a TE rep about the connectors, and unfortunately they do not make a male receptacle side. I guess the designers have to build the receptacle into their devices, eg this sensor.

So, (a) I'll have to think of another route, beyond the non-destructive "just plug in an extra harness" route, or (b) find another mating housing that works solidly and won't unlock, since this is still a 0.1" standard-pitch connector.

For now, I'm proceeding with using a standard 0.1" Molex male connector on the vehicle side, and the TE female connector on the sensor side.

 

[jblc]

Starting new thread here, given results from first attempts point to a new line of discussion.
@airline tech

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