Fan speed turning down on its own

[GreyAreaRanger]

Well, I have a newish issue with my Ranger. As the title states, I will randomly have my fan speed turn itself down from full. It typically happens 5-10 seconds after a bump, but not reliably enough to replicate. This has happened a few times before, but it was so sporadic that I shrugged it off as a glitch. In the last month, it's happened each time I've driven it. It will only do it one time until I turn it off and use it again. Any ideas? I know HVAC systems in these things are problematic and expensive, and as far as I know, the HVAC hasn't been serviced, and it has 112k on it. My extended warranty ends at 116k miles, so I would love for it to be covered, but I might be pushing my luck on that after they covered a trans replacement twice already.

As a side note, when I come home from work, if I am in the second-from-the-right lane going over a particular overpass, the bump there will also turn down my fan speed and turn off my cruise control, but only in that lane and at that overpass. Speed doesn't matter. Discovered that fun tidbit after I started working in the med center last year.

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[RangerBill]

I would scan for any DTC codes with Forscan. Which HVAC system do you have (Auto, Dual control, Manual)? If both cruise control and the fan speed change at the same time after going over a bump, it looks like a loose connection common to both systems.

 

[GreyAreaRanger]

I should have specified that I have the base radio (4" screen) in an XLT. The cruise control only turns off at that very specific lane and over pass, otherwise I have never had it turn off without me hitting the brakes or turning it off myself. The fan speed will do it randomly, such as pulling into my driveway an hour ago.

 

[ScarzRanger21(2.0)]

If it’s only happening when you hit bumps, it might be a loose connection somewhere that’s getting jostled around.

 

[RangerBill]

I should have specified that I have the base radio (4" screen) in an XLT. The cruise control only turns off at that very specific lane and over pass, otherwise I have never had it turn off without me hitting the brakes or turning it off myself. The fan speed will do it randomly, such as pulling into my driveway an hour ago.

Was anything spilled into the fan speed switch?

 

[GreyAreaRanger]

If it’s only happening when you hit bumps, it might be a loose connection somewhere that’s getting jostled around.

Any idea where I should start or why the delay between the bump and fan speed reducing takkes so long?

Was anything spilled into the fan speed switch?

I have not, since I have owned it. Cannot speak to the prior owners

 

[RangerBill]

Any idea where I should start or why the delay between the bump and fan speed reducing takkes so long?

I have not, since I have owned it. Cannot speak to the prior owners

Check for DTC codes with a scanner such as Forscan.

 

[ScarzRanger21(2.0)]

Any idea where I should start or why the delay between the bump and fan speed reducing takkes so long?

I have not, since I have owned it. Cannot speak to the prior owners

Like RangerBill said, I would start by scanning for any codes to see if there’s any faults the truck is picking up. This is what I found when looking up your issue/symptoms

Common Causes
Loose Blower Motor Connector: The plug supplying power and ground to the blower motor under the passenger-side dash has shaken loose or has corroded pins.

Worn Blower Motor Brushes: Internal components inside the blower motor are worn out; a physical jolt can cause them to lose proper contact and slow the fan down.

Faulty Resistor / Speed Controller: The blower motor resistor or pulse-width modulation (PWM) speed control module has a cracked solder joint or loose wiring harness that reacts to vehicle vibration.

Chassis Ground Issue: A loose or dirty ground point near the passenger footwell or kick panel loses solid contact momentarily over bumps.
How to Diagnose and Fix

Access the Blower: Empty the glove box, unclip it to let it drop down, and look up under the passenger-side dashboard to locate the blower motor and its wiring plug.

The Tap Test: Turn the AC fan on, and gently tap or wiggle the housing/wires of the blower motor by hand. If the speed changes, drops, or jumps back up, you have isolated a bad connection or failing motor.

Inspect the Plug: Unplug the electrical connector at the blower motor and resistor. Look for signs of melting, loose pins, or corrosion, then clean and secure them tightly.

Replace Parts: If the wiring and plug look solid and tight but tapping the motor replicates the slowdown, the internal components are failing and you will need to replace the blower motor.

 

[RangerBill]

Here is a picture of the Blower Module and its connector:

 

[GreyAreaRanger]

Looks like I got list of things to look at this weekend, thank yall! In case you couldn’t tell, electrical, or modern cars in general, ain’t my strong suit.

 

[Grandaccess]

I have noticed when I answer the Cell Phone it comes off of High, sometimes when I hang up it does not go back up, just a small bump in the matrix

 

[GreyAreaRanger]

I have noticed when I answer the Cell Phone it comes off of High, sometimes when I hang up it does not go back up, just a small bump in the matrix

If I can get my truck to actually route the call through the system it will do that but in those cases I know why it reduces the speed. Usually I get the message “ for your safety hands free is not available” or something like that.

 

[ScarzRanger21(2.0)]

I have noticed when I answer the Cell Phone it comes off of High, sometimes when I hang up it does not go back up, just a small bump in the matrix

Mine does this too, so does the wife’s ranger, and my f550 work truck. From what I’ve read, the truck turns the fan down when you’re on the phone to reduce background noise. If you turn the fan speed back up once you answer the phone it should turn up.

 

[GreyAreaRanger]

So yesterday it did it twice and both times it reverted back to the fan setting it was at when I turned on max ac while turning off max ac. Both times when it happened was on a smooth road so no bumps

 

[Superspirit]

Is it kicking out of max on time out? I know when I had my escape it kept kicking off recirc so I checked into it and it had a timer programmed in to kick it off and let fresh air in so people don't pass out for lack of oxygen in the passenger compartment. Just something you can look into in the owners manual.

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