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gray6811
Novice
Feb 23, 2014, 1:46 PM
Post #1 of 14
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vent system wont switch
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i have a 1999 dodge truck 4x4 360 motor my vent system is stuck on defrosters wont switch to heater or ac the heat and ac comes out throw the defroster and not come the other vents when i switch it to them
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Hammer Time
Ultimate Carjunky
/ Moderator
Feb 23, 2014, 2:03 PM
Post #2 of 14
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Re: vent system wont switch
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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.
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kev2
Veteran
Feb 23, 2014, 2:07 PM
Post #3 of 14
(2298 views)
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Re: vent system wont switch
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defrost is the so called DEFAULT positionn this is an electric actuator that drives the door. they are prone - guaranteed to fail .... when it comes to repairing this the attached video will guide you, the system 'cheats' will make it easy anyway it will explain what your dealing with
http://www.youtube.com/watch?v=w_mW722SNpA#t=233
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gray6811
Novice
Feb 23, 2014, 2:08 PM
Post #4 of 14
(2297 views)
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Re: vent system wont switch
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i was told that the vacuum hoes are good but something under the hood is the problem
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kev2
Veteran
Feb 23, 2014, 2:16 PM
Post #6 of 14
(2287 views)
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Re: vent system wont switch
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my text says electric for 1999 ?
a book with wrong info - never happens.... lets see what poster says.... any way I will try OEM resourses.
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Hammer Time
Ultimate Carjunky
/ Moderator
Feb 23, 2014, 2:20 PM
Post #7 of 14
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Re: vent system wont switch
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I know they are vacuum. I've changed enough of those evaporators.
- Description and Operation
Mode Door = vacuum
Blend Air Door = electric actuator
Fresh/Recirc door = vacuum
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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.
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gray6811
Novice
Feb 23, 2014, 8:11 PM
Post #8 of 14
(2263 views)
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Re: vent system wont switch
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where is the electric actuator located is it under the hood near the engine
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Hammer Time
Ultimate Carjunky
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Feb 23, 2014, 8:13 PM
Post #9 of 14
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Re: vent system wont switch
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It doesn't have an electric actuator for mode doors.
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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.
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gray6811
Novice
Feb 23, 2014, 8:22 PM
Post #10 of 14
(2259 views)
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Re: vent system wont switch
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you mentioned to me that the problem with my truck is the electric actuator the vent system is stuck on the defrosters and wont switch to the heat vent or come out of the ac vent
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Hammer Time
Ultimate Carjunky
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Feb 23, 2014, 8:24 PM
Post #11 of 14
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Re: vent system wont switch
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No, I didn't. Someone else did and they were incorrect.
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gray6811
Novice
Feb 23, 2014, 8:28 PM
Post #12 of 14
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Re: vent system wont switch
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i'm sorry i thought you mention that was my problem ? do you know what is possibly wrong with the vents
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Hammer Time
Ultimate Carjunky
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Feb 23, 2014, 8:30 PM
Post #13 of 14
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Re: vent system wont switch
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Are you not reading anything. I already posted how to find the problem and I even posted a picture of it.
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