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No air from rear vents

Discussion in '3rd Gen - 2007 - 2017' started by drokmofo, Sep 15, 2020.

  1. Trainmaster

    Trainmaster Old School Member

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    If the front is working fine and the rear's not, your Freon's fine. No need for gauges or any of that stuff.

    If the rear blower is not blowing you have an electrical problem, probably with the controller, fuse or rear blower motor. If the rear motor's running but you get no airflow you have a blend motor problem or maybe a clogged rear evaporator.
     
  2. 07navi

    07navi Full Access Members

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    He said the front isn't very cold and we all can use those gauges, especially him right now. Of course cold air won't fix the rear problem but he will need it eventually.
     
    Last edited: Sep 16, 2020
  3. drokmofo

    drokmofo Full Access Members

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    So, I got into the rear ac compartment and beat the fan motor a couple times with my hand and it kicked on. I can change the speed some by hitting it multiple times. Me caveman. Doesn't sound real smooth but it is flowing again. I'm going to add some r134 and see what the temp does. Going to price out the blower motor locally. Have it in cart on rockauto. I may still buy some gauges or borrow from bro in law....
     
  4. 07navi

    07navi Full Access Members

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    Like I said the gauges won't fix you rear ac problems but they are needed if you are going to maintain your AC system. You would pay more to have someone check it than a pair of gauges would cost plus you wouldn't learn anything. Let us know what your readings are and the ambient temperature.
     
  5. drokmofo

    drokmofo Full Access Members

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    I haven't put gauges to it but I did add maybe 16oz r134. Just idling in the driveway the temp got down to 65* at the front vents. The rear blower motor is all over the place with it's output. I put my arm in thru the cupholder tray and bang on it to increase flow. It was 104* today while I was working on this. I will be ordering a new blower motor from rock auto. $75 for a motorcraft blower and $27 for the resistor. Should I get the resistor? Thx for your continued input 07navi
     
  6. 07navi

    07navi Full Access Members

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    IDK about the resistor, probably not. Wow that's 40* colder than outside, I'm lucky to get it 25* colder at the vents on the freeway. Be careful adding refrigerant without the gauges though, you can slug the compressor and destroy is with too much. At those outside temps your high side will be well over 200.
     
  7. drokmofo

    drokmofo Full Access Members

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    I will take your advice with the gauges. Thank you much appreciated.
     
  8. Trainmaster

    Trainmaster Old School Member

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    Pull the resistor and make sure a loose connection on it isn't your problem before buying parts.
     
  9. 07navi

    07navi Full Access Members

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    He beat on it and got it going. Is the resistor attached to the unit? What does it do?
     
    Last edited: Sep 20, 2020
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  10. Trainmaster

    Trainmaster Old School Member

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    I'm not sure where the resistor is on the rear blower. On the front blower it's mounted on the plenum box with the resistor coils in the airflow to cool them. The resistor consists of a series of open resistance windings that are switched in and out of the fan circuit to vary the motor voltage, controlling the speed. Since they get very hot from the current flow, they are not soldered but crimped together. Sometimes the crimps and corrosion get the better of them or the coils split and they open up, responding to the pounding that the OP described.

    So if the resistor is anywhere near the rear motor, it should be checked before the motor is assumed to be the culprit. Locate it and fiddle with it to see if the internal connections are intermittent.

    For all I know, newer models may be a different design -- electronic stuff that is not plagued by these problems. The last one I've dealt with was in a 2000, and that had conventional windings.

    Here's a traditional blower resistor from a 2010 Explorer. The coils project into the plenum. See the crimps? The little semiconductor is a temperature fuse that opens if the thing overheats, as it may if airflow is obstructed.

    [​IMG]
     
    Last edited: Sep 21, 2020
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