Heat blower will not operate?

Tiny
TREEMAN1977
  • MEMBER
  • 2003 FORD F-150
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 290,000 MILES
The fan speed had been fluctuating for quite some time, seemingly with engine rpm. Most often when at low rpm. Today, after stopping, the blower motor will not operate at all when I restarted the engine. The fuse in the underhood box is good. I have the auto climate control, which has only operated on defrost for quite some time.
Tuesday, December 12th, 2017 AT 9:33 AM

5 Replies

Tiny
STEVE W.
  • MECHANIC
  • 15,432 POSTS
There are multiple fuses and relays in that system. Go through all of them and make sure they are not blown. If the fuses are all good when tested then it is likely that the control head has failed. The issue then becomes which option package you have as to getting the correct control head or having yours repaired.
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Monday, April 19th, 2021 AT 11:12 AM
Tiny
TREEMAN1977
  • MEMBER
  • 3 POSTS
I checked all of the fuses and relays first. Since asking the question, I went ahead and tested the voltage being supplied to the blower motor control module which tested at 12.1V. This told me that at least one of my problems was there, as a max of 8.3v was being supplied the blower motor when the fan speed was on high. Replacing the module fixed the problem. I did also source a used HVAC control head to hopefully fix the other issues with the system, I have not installed it yet. A note for this job is the module for the auto climate control will cost $175.00 to $250.00. You will wish you had the control knobs! You also will need to be proficient at using a multi-meter to test to narrow down the possibilities. The only info I could get for the tests was very technical written test procedures from the Ford dealership system.
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Monday, April 19th, 2021 AT 11:12 AM
Tiny
STEVE W.
  • MECHANIC
  • 15,432 POSTS
At least you can get the parts. Ford had a lot of option packages with different controls integrated into the control heads. Some of those versions are not available at all. One person earlier had an option set and searching the entire US there was 1 used control that matched. Ford doesn't have the parts either. One owner got ticked and went to the state and then federal route and Ford decided to have a company build a one off replacement.

Testing can be very involved with some items, especially when the companies won't give out the information.
Good job at repairing the issue.
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Monday, April 19th, 2021 AT 11:12 AM
Tiny
TREEMAN1977
  • MEMBER
  • 3 POSTS
Thanks. Yes, They were very reluctant at the dealership to give the information I needed but having gone to high school with the service manager helped my cause. My next truck will be a stripped down work truck. Appreciate your help.
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Monday, April 19th, 2021 AT 11:12 AM
Tiny
STEVE W.
  • MECHANIC
  • 15,432 POSTS
You're welcome. Sounds like you are willing to dig in and know how to do testing, if you run into other issues, post with the issue and any tests, if you need wiring or specific testing info we can likely get it for you.
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Monday, April 19th, 2021 AT 11:12 AM

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