Is my AC Dial working properly?

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acolic

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Hi

When I turn the dial I only really hear the fan at the last setting and it’s really powerful.

Is that normal?

39639d6860bf85f76ab73039b4b018c5.jpg

It’s a used truck and I am not sure if I should notice the fan in the first three settings.

And is the fan switch a separate component I can change?

Thanks for the info.


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Mike Murphy

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You should feel air in the vents on all speeds. Verify the blower motor is not operating on said speeds and then make sure to check the voltage at the blower motor/blower resistor on all speeds before you condemn the switch. If the truck is an 07 it should look something like this.

vaAFkDq.png
 
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The last setting is certainly the loudest by far, but if you only feel the air on the last setting, and not the first three, then chances are your blower motor resistor is done for. At least that is my educated guess. (The last setting bypasses the resistor, which is why you will often only have the last setting working when it goes out. And mine did the same thing.)

It is actually fairly common for them to go out and they’re a cheap fix. Maybe $20 at the most, and they’re super easy to replace. They’re held in by a couple screws up underneath of the glovebox area. You will see a wire plugged in to a black rectangle. Cant miss it.
 
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acolic

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Thanks

Where is the blower motor resistor block located?

Is that replaceable ?

Thanks for the info.

Alex


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acolic

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Thanks I found it.

I love all the knowledge on this forum.

Thanks

Alex


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acolic

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So that I’m a bit self sufficient, and perhaps help some others in the future, could someone explain using that attached electrical schematic the areas in red?

708765519d05f842b84027f89713fe4c.jpg



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Starting from the top circle, the C70, C71, C72, C73 are the names of the individual circuits. The next line down with the 10, 14, and 16 are the gauge thickness of wire that is being used in that circuit, and the bottom line DB/YL, DB/VT, DB/OR, DB/BR are the colors of the wires. (Dark Blue/Yellow, Dark Blue/Violet, Dark Blue/Orange, Dark Blue/Brown).

Not sure if the S3224 was included, but ill touch on it anyways. The black dot labeled S3224 is a splice, meaning two wires are basically tied or soldered together.

Moving down, C200 is the name of a connector plug along the circuit. If you download the factory service manual you can look up the connector, what it looks like, and what each pin goes to. The two upward arrows with a small 1, 5, 6, and 3 are the corresponding slot that the wire plugs into in the connector. (The factory service manual, which can be downloaded in pdf form somewhere on this forum has pictures and pinouts of all the connectors in the truck. It is incredibly useful.)

Moving down to the arrows at the AC Controller labeled C2. Those are the second connector on the AC control unit and again the wires are numbered based on the slot in the connector. The service manual will have a picture of the C2 AC controller connector so you know which connector is which.

The 1, 2, 3, 4, 5 inside the box are the different settings for the blower motor. Off, low, medium 1, medium 2, and high. The part that looks like the arm of a clock is the knob that you turn to select the setting.

Hope that helps you and others along the way!
 
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acolic

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That’s amazing.

How would you troubleshoot the resister block?

Does the diagram list the expected resistance at each position?




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The manual just says continuity between the pins for each setting, it doesn’t list a resistance.

I personally would pick up one from a junkyard for $7 or the parts store for $15-$20 and replace it to see if that is the problem.

The resistors are made out of ceramic heat sinks and get EXTREMELY hot. Over time the heat will warp and break the circuits and even the ceramic in the resistor, resulting in no juice to your motor. When mine started going out I would intermittently be able to use the lower settings, but not always. When I tested the resistor, they all had continuity, but I guess it was just in one of those ‘intermittent’ moods. When I replaced it with a junkyard pulled one everything worked again.

Here is the quick excerpt from the manual.

OPERATION
The blower motor resistor is connected to the vehicle electrical system through a dedicated wire lead and connector of the HVAC wire harness. The blower motor resistor has multiple resistor wires, each of which will reduce the current flow through the blower motor to change the blower motor speed.

The blower motor control for the heating-A/C system directs the ground path for the blower motor through the cor- rect resistor wire to obtain the selected speed. With the blower motor control in the lowest speed position, the ground path for the blower motor is applied through all of the resistor wires. Each higher speed selected with the blower motor control applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed.

The blower motor resistor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
 
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