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1999 Taurus - A/C blows warm air through vents - defrost blows cold air


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waterhbk
New User

Jun 1, 2012, 9:30 AM

Post #1 of 3 (2844 views)
1999 Taurus - A/C blows warm air through vents - defrost blows cold air Sign In

1999 Ford Taurus, 24 Valve, 142,000 Miles

A/C started blowing warm air through the vents. Took to shop which recommended replacing compressor, evaporater and a few other parts. Decided not to spend the money on a 13 year old car. Next day needed to use the defrost to clear windshield and the system blew out cold air. Switched to A/C and system continued to blow cold air through vents. Following day A/C back to blowing warm air. Switched on the defrost which produced cold air, changed to A/C and cold air continued.

A few months ago heard a leaf rattling in defrost. Sound is now gone. Is it possible that the leaf has dislodged and moved to obstruct a valve in the duct letting warm air through the vents? Have seen other posts with similar problems mentioning a vacuum leak not allowing the ducting valves to open/close properly. Should I look there or is the system really going as the shop indicated?

Thanks


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 1, 2012, 12:25 PM

Post #2 of 3 (2798 views)
Re: 1999 Taurus - A/C blows warm air through vents - defrost blows cold air Sign In

   The mode selection is done through a series of air doors that are operated by vacuum. When there is either a partial or total loss of vacuum, the system will default to either defrost or on some vehicles, heat. Acceleration can also have an effect on the doors for the same reason.

Look under the hood for a small black plastic hose coming through the firewall. Follow it to the vacuum source looking for any breaks, cracks or leaks. Also follow any other lines that branch off because they may go to a vacuum reservoir (storage tank) and a leak there will cause the same problem. Using a vacuum gauge to determine if you have full vacuum at any given point is the best way to find it. You can cut into the line anywhere and splice it back together with a piece of vacuum hose. Find the broken line, you found your problem.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



waterhbk
New User

Jun 1, 2012, 12:40 PM

Post #3 of 3 (2791 views)
Re: 1999 Taurus - A/C blows warm air through vents - defrost blows cold air Sign In

Thanks, I'll give it a shot.






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