Heater only blows on defrost

Tiny
F150FXRGUY
  • MEMBER
  • 2003 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 230,000 MILES
Electronic climate control unit. Heater is currently only blowing on defrost. A/C works good on vents, floor and defrost. Heater will not blow on floor. I replaced the heater unit once and it worked ok for about 6 months, but then defaulted to the same defroster setting only. Is this a vacuum leak or did the ECU fail again? I now have 2 suspect failed heater units. Are these repairable? If it's a vacuum leak, where should I start looking?
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Sunday, June 20th, 2010 AT 11:58 PM

1 Reply

Tiny
KASEKENNY1
  • EXPERT
Yes, this could be a vacuum leak. I would suggest going to the panel/floor actuator and pull the line off and put a vacuum gauge on it and then turn the system on. If there is no vacuum on the gauge then you most likely have a vacuum leak.

Here is a guide that will help explain this as well:

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

I attached the process for your review. Let us know what you find. Thanks
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Monday, April 19th, 2021 AT 3:01 PM

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