2009 F150 XLT
For the last two years, I have not had low speed on my blower motor, so I finally broke down and replaced the resistor and had the full range of speed for a grand total of one day. Since then, I have replaced the resistor (aftermarket) twice with the results being that it fails and only works on high speed. If I put the factory resistor back in, I have all speed except for low. My assumption at this point is that something is faulty with the blower motor. A static ohm test on the motor yields .4 ohms of resistance. A voltage check at the source with the resistor in line yields 7.15 V at level 1. 11.15 V at speed level two and three. And 12.12 V at speed level four. Thoughts, suggestions or otherwise? I have already ordered a new blower motor.

 

Your 2009 has an HVAC module that sends signals to the resistor based on the fan switch selection. Since the low setting works sometimes, I suspect the HVAC module is bad.


Here is the wiring diagram:
https://charm.li/Ford/2009/F%20150%2...trol%20System/

I don't know if a new module needs "programming" with IDS or Forscan. A low tech, low cost solution is to remove one from a junkyard truck. You need to make sure the truck has the same type of HVAC controls. Also check the part number on the module when pulling it from the junkyard.

 

Don
I don’t have low speed sometimes. I don’t have it at all. The only exception has been when I put a new blower resistor in. It’ll work for a day or so then nothing… only works on high at that point. This would seem to suggest the module is working 🤷🏻‍♂️

 

The HVAC module has four separate outputs, one for each speed . Test the outputs on the module. You may find nothing is output for the low speed and the module is bad. While you have things apart, you can verify the wires between the module and the resistor pack are good.

A quick way to test is measure the wiring at the resistor pack and verify each speed setting is sending power to the resistor pack.

 

trying again… I slapped a new blower motor in and tested with the old, factory resistor; works 2-4.
so I put in a Duralast resistor and at this 10 seconds it works on all speeds.

this would seem to rule out a module issue, would it not?

I will note that when testing voltage input at the resistor input harness, at all speeds I only received 12.2V to the yellow/red terminal

 

Looking closely at the blower motor resistor pack, the motor speed is determined by which wire on the module is providing a connection to ground.

It's difficult to explain why swapping resistors causes the low speed to work. There could be a component that gets reset when the resistor is disconnected from the module and then eventually stops working. The components in the module are probably solid state like transistors etc. and they can "almost" work sometimes.

You can try swapping resistors multiple times to see if there is any correlation to when the low speed works. You may also have a bad wire or connection that you temporarily "fix" when you are replacing parts. If you have a test light, connect the alligator clip to +12 and probe the module outputs as you move the speed switch to see if they are providing a ground.

 

A little update here. It was the resistor all along. After my 3rd aftermarket resistor failed even with a new blower, I decided to role the dice on a factory Ford unit. Got it, put it in, & it’s been working for the last week. - which is a week longer than the other units. So if anyone runs into a similar issue, spring for the factory resistor and skip the headache

 

Thanks for the update. It's not surprising the aftermarket parts were bad , but it's frustrating and unacceptable. When OEM is not available what are we supposed to do? I have become a fan of the self serve junkyards but that's definitely more work than a couple of clicks on Amazon.

 

Reading down through this post I asked myself, why not try a factory resistor..... seems like you figured that out, congrats.

 

anymore it’s a crapshoot if the stuff from Oreilly or Autozone will do the trick. Sometimes they’re great. Other… well, see above

 

Yes, they are my last option. I always shop Ebay for a factory one if I cant find a local deal from the dealer. Of course it helps to be a retired Ford tech.

 

Thanks for update. Always helps others.

 

My son has recently had problems with the heater resistors going bad on his 2012 F150.
Replaced the resistor in May 2025 - that went bad, so he took it to the Ford dealer who replaced the resistor and Body Control Module (BCM). The resistor went south again - it appeared to be cracked. Also had the blower motor replaced - these were done by the FORD dealer. The resistor went bad again, which was not such a big deal since a heater, A/C is not really needed during the summer in Maine. But now its getting chilly. He keeps taking the truck to Ford (as recommended by Midas) and since June 2025 has had 17 !! resistors replaced.
That's not a typo - seventeen.
A FORD rep said that there has been a "bad batch" of resistors, but even though the part is warrantied for a while he is charged for "service".

This sounds like a scam - or incompetence.
It's like going to the dentist for a filling, which falls out after a few weeks and being charged for "service" to replace the filling.

Bad Batch of resistors?????

Does anyone have a similar issue with 2012 or thereabouts F150?

Any ideas would be great b/c it's getting cold in Maine now (December 2025).
I don't understand "newer" vehicles - anything that does not have a carb, manual transmission and distributor.

Thank You

 

High resistance at the pigtail connector will just keep blowing a new resistor.

 

Like HomerWinzlow mentions connectors get too hot because of resistance that will compromise the new resister.

Rock Auto carries kits non OE. But they have parts for when things go bad to replace multiple parts. They don't carry kits for the Motorcraft, just the blower motor/wheel.

Blower Motor Kit Blower Motor Signs of Failure:

• Weak Airflow from Vents
• Unusual Noises or Vibrations When Blower Is Turned On

Blower Motor Control Module / Resistor Signs of Failure:

• No Airflow from Vents
• Blows Air at Only One Speed

Features & Benefits

• Application specific design and precision engineered components for direct OE replacement
• High Temperature Harness to withstand heat (up to 257°F) caused by high currents
• OE style connectors for easy plug and play installation

Problem Solving Replacement - Do it Right the First Time!This application is prone to an overloaded or burned out Blower Motor Resistor and Blower Motor Connector, due to high heat or excessive draw from a failing Blower Motor. If these parts are not replaced together, the resistor or connector will likely fail again. This Problem Solving Replacement contains the necessary components for a successful, long lasting repair!
Is it the Blower Motor or Blower Motor Control Module / Resistor?The Blower Motor Control Module / Resistor controls the fan speed of the Blower Motor. When it fails, it can cause the Blower Motor to stop working and can cause confusion on which part is faulty.