01 grand cherokee ac/heater vent issues


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01 grand cherokee ac/heater vent issues

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c_elliott
User

Apr 10, 2011, 7:54 AM

Post #1 of 3 (2435 views)

01 grand cherokee ac/heater vent issues	Sign In

Ok my 01 grand cherokee has been doing something wierd for a while which has gotten worse lately.
Heres my problem

If i have my heat or ac on with the vents open to the floor or on the front vent it switches to the defrost vent whenever im going up hill or to put it simple whenever i give it anytype of gas. Ive tried to google the issue but cant seem to find anything related to this problem. Its really just bugging right now. It has 171000 miles on it. Is there anything to really look for that might be my problem? Any ideas?

Thanks for any help in advance

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Apr 10, 2011, 10:31 AM

Post #2 of 3 (2426 views)

Re: 01 grand cherokee ac/heater vent issues	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.

c_elliott
User

Apr 10, 2011, 7:45 PM

Post #3 of 3 (2415 views)

Re: 01 grand cherokee ac/heater vent issues	Sign In

Thanks for the advice ill check it out tomorrow

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