Anyone know what would cause my AC not to function when the fan is set to setting 1? On settings 2-4, it functions normally and blows cold. All other HVAC functions (defrost, vent, heat...) work normally when the fan is set to 1. I checked a couple threads but couldn't find a solution. I tried cycling the "recirculate air" button and that didn't do it. Any ideas?

 

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You didn't fill in your personal data, so I'm not sure of your year model. But here is a link that shows a how to for the blower motor resister. It is the most common problem for what you have described.

On different models the resisters re in slightly different locations, but this link will give you an idea where the problem is.

Note: The resister pack is on the ground side of the circuit, so to test it with test light, use a hot wire. It should light a test light in each switch position.

https://www.f150online.com/forums/ar...emtc-hvac.html

 

Alright, I'll try that. I remember reading that thread and seeing that it seemed to address an issue where the fan isn't working on certain settings for all HVAC functions. I was thinking mine may be a separate issue because it only occurred when using the AC.

 

The fan works at all speeds when in heat position?

 

Yup... Max AC is the only position it won't work on speed 1.

 

That is odd, but I've never tried mine at that speed on max. For all I know,it could be normal. If I remember, I'll check that the next time I crank up.

 

There is nothing in the design of the circuit that would cause speed 1 to fail only in MAX.... or any other single mode selection position.

 

I'd much rather replace a resistor over a condenser or something similar...

 

The only idea I can come up with, is the blower motor is going out. The brushes or bushings may be bad, causing the motor to require more amperage than the switch allows at the slowest setting.

 

Update: I replaced the blower motor resistor today and sure enough that did it. Before replacing it, I did confirm that my fan worked at speed 1 in the heat and in the defrost positions. It just didn't work at speed 1 when set to MAX AC. I couldn't tell you the first thing about the crazy science stuff inside that resistor thingy, but swapping it out did the trick. Just FYI for anyone that comes across the same problem.