1994 Jeep Cherokee Vents don't blow cold or hot

Tiny
HAPPYIN
  • MEMBER
  • 1994 JEEP CHEROKEE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 17,000 MILES
Had my heater core replaced and since the air is blowing because u can hear it but it doesn't come out the vents, defrost, floor and dash we took dash off and the air is blowing but not thru vents plz help me Linnea
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Monday, October 4th, 2010 AT 7:11 AM

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Tiny
WRENCHTECH
  • EXPERT
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.

Given the history of this, you may want to look for pinched or disconnected hoses under the dash.
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Monday, October 4th, 2010 AT 7:34 AM
Tiny
HAPPYIN
  • MEMBER
We have taken the dash off and checked every hose and flapper plus the vacunm hose to no avail could it be the control box? When we have dash off u CAN feel it on the defrost and at u're feet thanks Linnea
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Monday, October 4th, 2010 AT 7:46 AM
Tiny
WRENCHTECH
  • EXPERT
What is the vacuum reading on the supply hose?
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Monday, October 4th, 2010 AT 4:38 PM
Tiny
HAPPYIN
  • MEMBER
I'll have to get a gage can I get one at Auto Zone etc thank u very much
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Monday, October 4th, 2010 AT 7:12 PM
Tiny
WRENCHTECH
  • EXPERT
Yes, most any parts store will have them. Some rent or loan them.
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Monday, October 4th, 2010 AT 7:13 PM

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