AC problems

[bmnelson23]

I have a 99 ford expedition, 5.4 4x4. AC works fine unless the car sits in the sun parked and turned off for a few hours. If it has been in the sun, upon starting the car, the AC and the blower motor do not turn on. After running the car for 10-20 minutes, the AC will kick on perfectly. This happens in the summer and the winter. The Heater will always turn on regardless of being in the sun or not during the summer or the winter but the AC will not turn on in the summer or winter if it has sat not running in the sun for a few hours. If the car is parked in the garage, regardless of summer or winter, the AC kicks on every time. Any help is greatly appreciated. Would a faulty resistor motor behave like this if it got too hot? Is there a sensor somewhere that is causing the AC and blower motor to not turn on? Help.

 

[99WhiteC5Coupe]

I have a 99 ford expedition, 5.4 4x4. AC works fine unless the car sits in the sun parked and turned off for a few hours. If it has been in the sun, upon starting the car, the AC and the blower motor do not turn on. After running the car for 10-20 minutes, the AC will kick on perfectly. This happens in the summer and the winter. The Heater will always turn on regardless of being in the sun or not during the summer or the winter but the AC will not turn on in the summer or winter if it has sat not running in the sun for a few hours. If the car is parked in the garage, regardless of summer or winter, the AC kicks on every time. Any help is greatly appreciated. Would a faulty resistor motor behave like this if it got too hot? Is there a sensor somewhere that is causing the AC and blower motor to not turn on? Help.

Does the a/c system compressor not run AND the HVAC blower motor not run when this happens, or only the blower motor?

Do you have rear air? Does the rear blower motor run when this happens?

A defective blower motor speed control (resistor unit) usually only affects the front HVAC blower motor.

Have you examined the wiring connector at the blower resistor and also at the front HVAC fan motor?

These links may help you:

https://static.nhtsa.gov/odi/tsbs/2019/MC-10163573-0001.pdf

And

How To Replace Blower Motor Wiring Harness 2007-2017 Ford Expedition

Shop for New Auto Parts at 1AAuto.com https://trq.video/c-157-ahThe heat and air condition fan is controlled by a separate module, called the blower motor re...

www.youtube.com

 

[bmnelson23]

Thanks for your response. The compressor does not engage if it has been out in the sun. Once the car is driven, it engages and then the controls on the dash begin to blow cold air. I do have rear air but those don’t turn on either if it has been sitting in the sun. I am truly baffled by this. The system works great as long as the vehicle is covered by a tree or garage, out of the sun. But if it sits in the sun, the clutch on the compressor does not engage, the air blower inside won’t blow any air or even turn on, until the car runs for 10 to 20 minutes.

 

[99WhiteC5Coupe]

Thanks for your response. The compressor does not engage if it has been out in the sun. Once the car is driven, it engages and then the controls on the dash begin to blow cold air. I do have rear air but those don’t turn on either if it has been sitting in the sun. I am truly baffled by this. The system works great as long as the vehicle is covered by a tree or garage, out of the sun. But if it sits in the sun, the clutch on the compressor does not engage, the air blower inside won’t blow any air or even turn on, until the car runs for 10 to 20 minutes.

A long shot. Have you checked to see if all fuses and relays are fully seated in their slot for all electrical junction boxes?

On my 2015 - there was one box on top of the radiator - just under the hood. Sun and heat could cause one or more to expand or contract, and not make full contact?

 

[bmnelson23]

Good question and yes I have checked all of those.