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HVAC (AC) wiring diagrams

Tiny
LEE1977
  • MEMBER
  • 2014 FORD F-150
  • 3.5L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 80,000 MILES
AC blower does not work on max speed. New resistor, motor and cable. Works on all other speeds. When max speed is selected, it blows for a moment and shuts off until a lower speed is selected. Old resistor had signs of overcurrent on one of the pins. That is why I replaced all components. System used to shut off at all speeds. Now, just highest setting fails.
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Tuesday, August 7th, 2018 AT 5:28 PM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Hello,

It sounds like the HVAC control head is losing signal, but to be sure here are the wiring diagrams so you can see how the system works and a guide on how to test it. If it tests bad I would try a used control head so you might need not to reprogram it. If so it will cost about $130.00 at the shop. Also, when you say resistor you mean the motor speed control? Were the parts OEM?

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Please let us know what you find.

Cheers, Ken
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Thursday, August 9th, 2018 AT 3:19 PM
Tiny
LEE1977
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No, parts were O'Reily. Yes, by resistor, I mean the motor speed control.
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Thursday, August 9th, 2018 AT 4:28 PM
Tiny
KEN L
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It sounds like the speed controller is out again so you may have got a bad one. Try to take it back and if the new one works then you know what the problem is.
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Friday, August 10th, 2018 AT 10:55 AM
Tiny
LEE1977
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Replaced the resistor again today (third time) and the problem still exists. Although, I may have narrowed it down. It only shuts off when the recirc is on at the highest setting. Almost as though there is a restriction in the duct and it causes the blower to pull too many amps and trips.

If the recirc is off, the fan works on all settings.

Any thoughts?
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Sunday, August 12th, 2018 AT 6:58 PM
Tiny
KEN L
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When the blower is on high and working can you feel the wires going to the blower motor to see if there are warm?
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Monday, August 13th, 2018 AT 12:55 PM

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