2003 Ford F-150 Heater only blows on defrost

Tiny
F150FXRGUY
  • 2003 FORD F-150

Heater problem
2003 Ford F150 V8 Four Wheel Drive Automatic 230000 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

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Tiny
JACOBANDNICKOLAS
  • EXPERT
  • 68,398 POSTS

I would start with the idea of a vacuum leak. Start by checking under the dash and the hood. That would be my first guess.

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Monday, June 21st, 2010 AT 12:12 AM

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