Question about 2003 Dodge Durango

3 Answers

AC light comes on only at highest fan setting. Just started this behavior today. Previously AC would come on upon activation at the lowest through highest fan speed selection.

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  • ajg047 Jun 27, 2009

    Thanks for the suggestions. I'm quite sure the compressor is working properly. The issue seems related to the fan switch itself.
    Here's my guess as to how the AC activation circuit works: Under normal operation the AC gets a signal from the fan switch ... so the compressor is activated only when the fan is blowing. Right now the AC light (and compressor switches on) only at the highest fan setting.
    My original thought was that the fan switch might be a gang-style switch and somehow the compressor activation contact gang somehow became fouled. Your solution suggests a more sophisticated electronic control (as opposed to my guess at a mechanical control mechanism) in which a resistor could have failed. Am I on the right wavelength here?

  • ajg047 Jun 27, 2009

    Trying to locate the resistor. I see a two wire cable connector going to the motor itself, a small guage multi-wire connector going to something (maybe a temp sensor) in the air plenum, and a multi-wire (approx #14 guage) connector going to a rectangular plate secured to the blower assembly by 2 screws. Could it be the latter? Kind of hard to do this without reference to a drawing or chematic. I can send a photo of the blower assembly if it would help you assist me in identifying the resistor.

  • ajg047 Jun 27, 2009

    AC works only when blower control is set to high. Blowers works at all speeds but the AC light (and compressor is engaged) only when the high blower setting is selected. Previous expert thought it was the blower resistor. But looking at the wiring schematic it seems if the resistor was bad wouldn't one or more of the blowers speeds not work?
    Problem to be solved - why doesn't the AC work at all blower speeds ... only engages when blower is at high speed.

  • ajg047 Jun 27, 2009

    Arghhhh!
    THE AC WORKS FINE! The problem is, it only works when the blower switch is set on HIGH.
    The blower itself works at all speeds. BUT the AC indicator light (on the AC engage button) only illuminates (and the compressor only engages) when the blower selector is set on HIGH.
    To reiterate ... the AC works fine ... its not a freon/charging problem ... its not a compressor problem


  • ajg047 Jun 27, 2009

    This is hopeless. AC = air conditioner ... NOT alternating current
    Why in god's name would you reference an article on resistors in alternating current circuits? It has absolutely no bearing on the problem.

    NONE OF THE RECOMMENDED SOLUTIONS ARE ACCEPTABLE


  • ajg047 Jun 27, 2009

    Thanks for the help

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  • 615 Answers

The first thing I would do is check the A/C system Freon level and pressure with A/C gauges. If you have a small Freon leak in the system and enough Freon has leaked out the low pressure A/C switch will not allow the compressor to come on.



Sometimes with the new R134A Freon systems just a small amount of Freon added to the system will be enough to allow the compressor to come on. You should then have the system checked for a Freon leak, since it is NOT normal to have to periodically add Freon to the system.



If the Freon level checks out OK and you still have problems I would then test the electric cooling fan motor that is up in front of the radiator. This electric fan is needed for the A/C system and the fan should be ON when the A/C compressor is ON. This fan is controlled by a relay and gets a signal from the A/C control head inside the vehicle and the on board computer.



Unfortunately both suggestions are not very easy to test yourself at home and really should be done by a trained mechanic, unless you know what you are doing. Adding too much Freon to the system can do damage.

Posted on Jun 27, 2009

  • Chandrashekhar N.G
    Chandrashekhar N.G Jun 27, 2009


    http://www.physclips.unsw.edu.au/jw/AC.h...
    visit here it shows how AC Circuit Works

    so it means



    may be your problem is in all probabilities the FAN SPEED RESISTOR.

    It looks like it has 3 or 4 springs mounted on a plastic board and will fit in the palm of your hand.

    This will be a dealer item as most auto parts stores do NOT carry this component.

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Check for a ground. My wipers will work like heck on high, but unless the ground wire on the switch is hooked up I get no lower speeds. On the CJ heaters there is a resistor for lower speeds, and that would be another place to look.

Normally when the blower is only working on low or high it's more than likely your BLOWER MOTOR RESISTOR

Ninety-eight per cent chance that was the fan speed resistor. I bought one on ebay for $27 and replaced it in about 10 minutes. You need to drop the glove box by pushing in the holder clips. Inside you'll see a part with several wires held to the heater housing by two bolts. Remove the bolts, turn around the assembly, and there's your resistor, ready for replacment. Piece of cake.
-sultan

Posted on Jun 27, 2009

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To check a fan clutch condition the engine must be off. Inspect the fan clutch for leakage at the front or rear of the unit (input shaft and temperature controlled expansion spring). If leakage is observed the fan clutch has failed and needs replacing. Next, take the fan blade and turn it, the fan blade should free wheel, if you cannot turn the fan blade the clutch has locked up and needs to be replaced. Also, there should be no or very little play as you turn the fan, if excess play exists replace the fan clutch.
How to Replace a Clutch Fan

  • Start with the engine off and in cool condition
  • Remove all obstructing shields or brackets to gain access to the fan clutch
  • Loosen and main mounting bolts that mount he fan clutch to the water pump
  • Remove all related drive belts and finish removing the fan clutch mounting bolts
  • Remove the fan clutch and loosen fan mounting bolts
  • Separate the fan from the clutch, reassemble as needed.
For manufacturer replacement procedures for your particular car consult


If the fan only works on high, the most common cause is a bad blower motor resister. It will either be on the passanger side of the firewall, or it could be in the blower box.









Have Freon check possible you are low. If youtake a look at the a/c compressor on the from is the clutch start thevehicle with a/c off he clutch won't turn. Now turn a/c on the clutchwill turn. If clutch cuts on and off every few seconds thats a goodindication of low freon.









Is the gauge on the high or low side hose? Youshould be charging from the low-side port. If the system is low onrefrigerant, the compressor will draw the low side down to a pressurethat is too low. A low-pressure cutout switch will cause the compressorto turn off to prevent drawing the low side into a vacuum. If there wasa leak in the system, drawing the low side into a vacuum could allowair to enter bringing along the humidity with it. Moisture in thesystem combines with refrigerant to form an acid which will destroymetal parts.

Once the compressor was switched off, high and low side pressureswill equalize, and the compressor will turn back on. The hissing you'rehearing is the refrigerant changing from a liquid to a vapor at thewrong point in the system. This is supposed to happen in the evaporatorin the dash board where you won't hear it.

A better way of observing the state-of-charge in the system is towatch the sight glass on top of the receiver / drier for bubbles. Youwill not see any bubbles when the system is very low on charge or fullycharged. In your case, you know it's not fully charged. The refrigerantwill go in much faster if you place the can in a pail of hot wa

Posted on Jun 27, 2009

  • 5 more comments 
  • mohammed marika thambi
    mohammed marika thambi Jun 27, 2009

    Recently, modern air-conditioners have begun to incorporate
    variable-speed compressors and variable-opening expansion valves,
    together with feedback control to improve the performance and energy
    efficiency. However, for the compressor there usually exists a
    low-speed limit below which its speed can not be continuously modulated
    unless it is completely turned off. When the air-conditioning system is
    operated in light-thermal-load conditions, the low-speed limit causes
    the compressor to run in an on–off manner which can significantly
    degrade the performance and efficiency. In this paper, a dynamic
    switching strategy is proposed for such scenarios. The strategy is
    basically an integration of a cascading control structure, an intuitive
    switching strategy, and a dynamic compensator. While the control
    structure provides the nominal performance, the intuitive switching
    strategy and the dynamic compensator together can account for the
    compressor’s low-speed limitation. Theoretical analysis reveals that
    when the output matrix of the dynamic compensator is chosen properly,
    the proposed strategy can effectively reduce the output error caused by
    the on–off operation of the compressor. Experiments also demonstrate
    that the proposed strategy can simultaneously provide better regulation
    for the indoor temperature and improve the energy efficiency at steady
    state.

  • mohammed marika thambi
    mohammed marika thambi Jun 27, 2009

    You need to replace the blower resistor located
    under the passenger side of the dash (glovebox). I had the same problem
    and this fixed it.



    4.7L Cooling fan always running when engine is, increases speed as rpms increase resulting in load roar. What part went bad








    fan clutch is bad


    its the part betwwen the water pump and the fan


    fan bolts on it

    Did you check the blower resistor














    Did you use a fuse or hard wire the A/C clutch
    to make it energize? Use a test lead with the same ize fuse in the
    line. If it bolws then the problem is the clutch. A straight wire is
    about 40 amps+ You can buy a fuse in a line for about 2 bucks




    You mean refrigerant level? It assume the static temperature of the
    engine compartment in punds. If you engine area is 125 degrees then the
    refrigerant will be 125 pounds and it is norma


  • mohammed marika thambi
    mohammed marika thambi Jun 27, 2009

    Check the fan relay in the power ditribution center, under the hood..can also be the ECT and the PCM.

  • mohammed marika thambi
    mohammed marika thambi Jun 27, 2009

    When you get it stoped does idle come back to 750?


    Have you checked throttle cable for sticking? Has throttle body been
    cleaned? If you blip the throttle in park does it stay up or retun to
    normal idle?


  • mohammed marika thambi
    mohammed marika thambi Jun 27, 2009

    I thought about doing this but I cannot figure
    out which one is the blower relay. The pictures on the fuse box are not
    very self-explanatory. Could anybody tell me which relay is the blower
    one? There are total 5 as far as I remember, 3 at the upper part and 2
    at the bottom of the fuse box

    Check operation of radiator fan. A partially
    plugged radiator may be causing your problem. Replace radiator with new, and
    your heater core may be partially plugged also.



    The heater control valve is on the top of the engine
    with a heater hose attached. Check for flow or coolant out of the valve.
    Test the heater core by checking coolant flow out of it.




    : The heater control valve is probably not opening. It controls
    the coolant flow from the engine through the heater hoses to the heater. The valve
    may be stuck or the vacuum hose may not be attached.


  • mohammed marika thambi
    mohammed marika thambi Jun 27, 2009

    Why does my
    fan motor work on high only?


    All cars are designed with a blower fan motor that pushes air through the
    ventilation system. This air is processed by a series of vents to direct the air
    to various positions. Example: heater, air conditioner and defrost modes. Most
    blower motors
    are power by a basic electrical circuit that utilizes a multi
    resistor or a solid-state resistor to control different fan speed modes (low,
    medium low, medium and high). If the resistor malfunctions it may lose one or
    more of the lower fan speed settings.



    • Turn the key to the "on" position (do not start the engine)


    • Inspect system fuse
      and replace if needed. Some cars utilize separate circuit fuses in the fuse
      box, be sure to inspect all fuses and replace as needed.


    • Remove the fan speed resistor component. This resistor is almost always
      located in the heater plenum so it can be cooled by the air circulating
      through the vents. After the resistor is removed inspect the resistor for
      obvious burn marks at any point. If any area shows signs of extreme heat it
      needs to be replaced. Also inspect the resistor connector for heat damage.
      Reinstall with new and recheck system.

    For exact specific repair procedures for any of the steps above visit our
    online repair
    manual
    page.

    Troubleshooting
    /

    Blower Fan Works On High Speed Only




  • mohammed marika thambi
    mohammed marika thambi Jun 27, 2009

    Check the cooling system, particularly the radiator
    to make sure it is not partially plugged. Additionally, check the radiator fan for
    proper operation. If the engine temperature is running way above normal, some of
    the heat is transferred to the air-conditioning condenser, which causes the air-conditioner
    to lose efficiency. As for your question about a "limiter" switch, there is a high-pressure
    switch in the air-conditioning system that cuts the compressor out when the pressure
    gets too high.

    You may have a cracked housing around the air-conditioning
    unit under the dash. If this is your problem, removing the dash is probably your
    only solution. Before you do anything more, have your mechanic check to see if the
    drain itself is partially plugged.

    www.2carpros.com/first_things/air_conditioner_not_working.h

    www.2carpros.com/first_things/air_conditioner_not_working.htmTurn the air conditioner to
    the "on" position and set controls to the coldest setting. Start the
    engine and
    allow to idle. Then open the hood and inspect the clutch at the front of the compressor,
    is it turning? "Engaged" if so, the system has enough refrigerant to activate. If
    the system is low on refrigerant it will not work properly. In this case an
    air conditioner recharge
    kit
    is needed to recharge the system. If the system is low on refrigerant it
    could cycle on and off, making a ticking noise. If the compressor clutch is not turning
    proceed to next step.



    Air Conditioner Compressor

    3. Inspect for Refrigerant Leaks -
    If the system has a
    large leak and no refrigerant remains it will not activate. First test system
    for a static pressure charge, with the

    engine off attach an
    ac gauge to the low
    side pressure port and check the state of charge. Depending on outside temperature
    there should be between 50 psi and 80 psi. (Cool and warm).




    Air Conditioner Pressure Gauge

    A refrigerant leak detector is needed to inspect for leak, but if you do not
    have a leak detector there is an alternative method. The
    air conditioner system
    is designed to run with oil suspended in the refrigerant to lubricate the system.
    Check for oily residue outside the system by inspecting all hoses, compressor, condenser
    ,
    evaporator or receiver drier and replace any component that has failed.





    Leaking Air Conditioner Hose

    NOTE: Before you replace any a/c component you must evacuate
    the a/c system of any remaining refrigerant. Replace failed parts as required,
    vacuum system with a vacuum pump and recharge using an
    air conditioner recharge
    kit
    . If system has sufficient refrigerant (134a) proceed to next step.


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