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air conditioning control
07-21-2011, 10:18 AM
Post: #1
air conditioning control
2004 jeep grand jeep Cherokee, 4litre straight 6. Air conditioning dial will be set on chest level , once in while it will move to foot level and change levels on its own without moving the dial . This does not happen all the time, periodically. Baffle problem, electrical, sensor ?? Any ideas would be great b4 I take it to a mechanic and have him change something out that doesnt need worked on.
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07-21-2011, 05:34 PM
Post: #2
RE: air conditioning control
Sounds like a vacuum issue. The different airflow diverters are usually controlled by vacuum motors. If you have a small vacuum leak the air flow will usually change with a heavy motor load like going up a hill or passing. This is because the vacuum drops as you open the throttle. If the leak gets big enough the air flow will usually default to the defroster as a safety feature.

You can usually find a vacuum line going through the firewall. That would likely be the one for the heater control. If you follow it back toward the engine you should come to a one-way valve and a vacuum reservoir. Then a line leading to a vacuum source at the engine. Look for loose connections, cracked lines, or a leak in the reservoir. If that is all good you could have a leak in the line or controls under the dash. A big enough leak should trigger the Check Engine or Service Engine Soon light.

Hope that helps. Please let us know what you find.

Thanks for using the forum,

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