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AC makes "ch...ch...ch" sound- 88 econoline

Discussion in 'Heating and Air Conditioning' started by aussie jason, Nov 5, 2017.

  1. aussie jason

    aussie jason Member

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    hi legends,

    whenever i slide the climate lever from anywhere like "vent" to "AC - cold" or "AC-max", after a few seconds i start to hear a loud "ch ...ch... ch... ch... ch" sound coming from the center of behind the dash area. it also seems to coincide with a subtle drop in engine power with each "ch". the ch sound was every few seconds but its getting faster, now its every second. it happens regardless of the blower being on or off.

    i currently also have a blower failure!, but this ch sound has been happening since before the blower issue. about 2 months ago i had the AC re-gassed. the Ch sound started not long after that. i told the gas mechanic and he hoped it might only be when it's very cold weather in the morning. however its warm now and still an issue.

    regards
    jason
  2. Action

    Action Moderator Staff Member Respected Member

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    Basic question - sound inside or outside vehicle?

    With the hood up engine running and transmission in park, see if you can hear it under the hood.

    >>>>>>>>Action
  3. aussie jason

    aussie jason Member

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    ok the noise is coming from that round background part attached to the right of the engine just above the radiator cap in the pic. (beneath the V pipe of the air intake). it has a belt around it. when the aircon is turned on that cog wheel stops and starts and the belt keeps going, slipping, making the ch ch ch ch sound.

    ch.ch.jpg
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  4. Action

    Action Moderator Staff Member Respected Member

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    That helps! That part is the AC clutch on the front of the AC compressor. Likely you are hearing the AC compressor. Or it could be the clutch engaging and disengaging.

    The AC will be on when the system is -
    On AC
    On max AC
    On defrost
    On floor/defrost

    Why? One of the functions of AC is to pull humidity out of the air. When in defrost position especially when real cold out, it is important to take moisture out of the air. Moist air on the inside of a cold windshield means ice can from on the inside of the windshield.

    Back to your issue. You may have an AC clutch failing or slipping. The clutch can be replaced without removing the refrigerant. OR could be the AC compressor.

    If the compressor is cycling frequently (clutch on and clutch off is a cycle) the system may be low on refrigerant. (gas) From the position that the picture was taken you can watch the clutch engage and disengage. With warmer temps the compressor clutch should stay engaged much longer then disengaged. Especially in MAX AC with the doors open.

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  5. aussie jason

    aussie jason Member

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    awesome thanks! the cycling is getting faster and faster, makes me think its getting progressively lower on gas. its starts the noise about ten seconds after starting the engine. i'll get the blower fixed first then take it in to the AC guy
  6. Action

    Action Moderator Staff Member Respected Member

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    "the cycling is getting faster and faster, makes me think its getting progressively lower on gas"

    Shorter cycling on times is an indication of low refrigerant charge. (Gas) The system may have a leak.

    >>>>>>>>>>>>>>Action
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  7. aussie jason

    aussie jason Member

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    i took this clip apart, the bit in my hand goes to the loom. the other end, im fairly sure goes to the blower. i was getting a reading of 12.8volts in this clip, when the blower was on speed setting 1. same for speed setting 3.
    however there is no fan happening. im assuming i have a broken blower fan motor and need to replace?

    ps. as mentioned at start of thread, there was a 30A fuse in the 15A slot and im wondering if this caused the broken blower.


    blower-wires.jpg
  8. Action

    Action Moderator Staff Member Respected Member

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    There is only two wires in that connector.
    The HVAC blower motor fan also has a resistor that has multiple wires
    The HVAC blower fan will take more current than 15 amps.

    What is the voltage when the fan is on low and the HVAC selector is turned to off?

    No fan .... could be
    Blower motor
    OR
    Blower motor resistor
    Assuming the fuse is good

    >>>>>>>>>>>Action
  9. aussie jason

    aussie jason Member

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    ok yeah so previous pic was actually the AC power, even tho it seems to connect directly to the blower motor!
    anyway, so i managed to get the blower resistor out without removing the battery or anything else. i had to unbolt the resistor before unclipping the wires, super tight fit!

    what im finding is im getting 12V to the white connector shown in pic on right. depending on the speed i set the blower to i get 12v to all the wires in that connector. the black/red is the ground.
    however, when i re-connect the resistor thing that i am holding in pic, i get no 12v readings through it. maybe i am using multimeter wrongly?

    i set multimeter to OHM and was able to get ohms through each of the resistor spring things and also the capacitor looking thing

    blower-resistor.jpg
  10. Action

    Action Moderator Staff Member Respected Member

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    That resistor looks good. The capacitor looking thing is a thermal limiter. (to prevent fires) I have seen resistors where they are burned from a connection coming apart internally at the resistor. If you are getting current through the resistor with an ohm meter my opinion is you have a good resister.

    If you have 12v+ at the resistor .... that 12+ is coming through a fuse and the HVAC function selector and to the blower motor.
    Blower motor gets 12v+ from a black/orange wire.

    If you have 12v+ at the orange/black wire, you just tested the blower motor and it is good! Or with the black/orange wire connected to the blower motor and the function selector in the cab set to anything except off, ground the orange/black wire and the blower should operate on high speed.
    Black/orange is 12v+ to motor
    Orange/black is ground side

    The circuit is ground side switched. From the resistor the current flows to the fan switch and ground. If that ground or the fan switch is bad NO blower motor operation.

    >>>>>>>>Action
  11. aussie jason

    aussie jason Member

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    i have this motorcraft blower:
    arepairguide.autozone.com_znetrgs_repair_guide_content_en_us_ib8818da973ccfde2a1ef995cb199d78a.jpg

    it has a gasket and completely seals the blower fan housing inside, so no "under hood engine air" circulates into the blower fan blades.

    the blower motor is cactus and i need a new one. i cannot find it anywhere, the only thing i can find is like this:

    https://www.ebay.com/itm/Genuine-OE...ash=item2a656b762f:g:kQMAAOSw8RJXDG~c&vxp=mtr

    new-blower.png

    this one seems to have exposed the air conditioning so that it is sucking in air from the engine bay???
  12. Action

    Action Moderator Staff Member Respected Member

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  13. Action

    Action Moderator Staff Member Respected Member

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    The correct one is sealed from the engine compartment. The picture may not be accurate and just a stock picture. It would be good to ask before you place an order.

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  14. aussie jason

    aussie jason Member

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    wow, this is really tough to find. the Cardone model is the one i need (w/Air, front) and it has the 'shroud'? to seal the AC compartment. However it's sold out. The company has no email contact shown, i might try calling them tonight (USA day time).

    im wondering if it's possible to have an electrician recondition my existing blower motor?
  15. aussie jason

    aussie jason Member

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  16. Action

    Action Moderator Staff Member Respected Member

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    That should work. And you will need to transfer the blower cage and end connector.

    Kind of a pain.

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