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04 pressure switch locations

Discussion in '2nd Gen - 2003 - 2006' started by Anarak, Sep 24, 2020.

  1. Anarak

    Anarak Member

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    I tried to search before posting and there is nothing on this anywhere on the web or here that I can find. 04; 5.4L EB ac is not working. I am a novice and do most work with the help of YouTube. So I have replaced the ac clutch and the relay, fuses. I have power at the high pressure switch but nothing at the comp clutch. It will not engage. When the only clutch went I foolishly self diagnosed with Google and added Freon to the system and it didn’t help. I removed a spacer from the clutch plate and that got it going. Well old parts go bad and the bearings on the pulley went out. So I’ve replaced the clutch and field coil but have no power at the clutch. I am troubleshooting one thing at a time and want to replace the pressure switches. I know where the high pressure switch is but have no clue where the low pressure switch is, and there is nothing on the web that is helpful, no parts on Amazon, Autozone, RockAuto, Advanced Auto have the same plug as the high pressure switch. Can someone please help me with location of the low pressure switch and maybe part numbers for both of them? Thanks in advance!
     
  2. Yupster Dog

    Yupster Dog Full Access Members

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    See if this helps.
     
  3. Hamfisted

    Hamfisted Full Access Members

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    It's screwed into the side of the front expansion valve. Kind of a pain to get to. But you can unplug it and check for power at the harness when you select the AC on. You have to buy the entire Motorcraft expansion valve to get the new switch, they're not sold separately.


    https://www.summitracing.com/parts/mof-yg386



    [​IMG]
     
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  4. Anarak

    Anarak Member

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    Guys thank you for the help. I may try this after I do the high pressure switch. Any ideas what else would be blocking power to the comp clutch?
     
  5. Hamfisted

    Hamfisted Full Access Members

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    There's a AC clutch relay up in the Aux-1 relay box, which is just under the stock air filter on the fenderwell. But I would check for voltage at the low pressure switch harness plug before I went changing out other switches that didn't need changing. If you don't have 12v at that low pressure harness plug then go check for voltage at the AC relay when you have the AC compressor switch on. (Are you getting a green LED illuminated there at the compressor switch on the AC head unit in the dash ?) .


    Aux 1 Relay Box on driver's side fenderwell under air filter ....
    [​IMG]


    [​IMG]
     
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  6. Anarak

    Anarak Member

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    I do have 12v at both switches high and low. I changed the relay (one of the first things I did) but I’m not sure how to check if there’s power to the relay. Which gaps do I check? I do have the little green light on the dash
     
  7. Hamfisted

    Hamfisted Full Access Members

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    Ok, I stuffed most of the EATC wiring diagram pages in this post. Look them over and maybe they'll give you a better direction to go. That relay is a WOT cutout relay. So you should see voltage at anything below WOT. Did you say you already replaced the low pressure / expansion valve assembly up front? Did you try jumping the low pressure harness there where it plugs into the switch? If you have ForScan software in your laptop you can plug into your OBDII port and see what signals are being sent by the PCM to your AC compressor. You just load the HVAC related PIDs from the PCM section, hit the "play" button, and watch the switches there. The ACP switch is your high pressure cutout switch (OPEN is normal). The ACCS is your low pressure cutout switch (CLOSED is normal). The WAC/ACCR switch is your WOT relay cutout (CLOSED is normal).
     

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    Last edited: Sep 26, 2020
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  8. Anarak

    Anarak Member

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    Ham, thank you so much for the post. I do have 12v at the low and high pressure switches. I did not replace either of the switches yet. I tried to get a low pressure switch and ended up with a high pressure switch, and it didn't fit either, smh... I did try jumping the low pressure harness, but it did nothing. Also tried jumping the high pressure switch, did nothing. If I did it right, should the engine be running? or just in the "on" position?

    I don't have ForScan, I have a handheld (simple) OBDII scanner, but it doesn't work with laptop. I may look into that, but not sure it's in the budget for this truck.

    If I purchase the replacement evaporator kit, can I remove the low pressure switch and put it in the truck without replacing the whole thing? Also, if I can, will I have to evac the entire system to make the change?

    Sorry for so many questions, I am just at wits end with this thing....
     
  9. Hamfisted

    Hamfisted Full Access Members

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  10. Don Hall

    Don Hall Full Access Members

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    Nice posting, Hamfisted. It is help/info, like you have provided, that makes these forums great. :waytogo::waytogo:
     
    Last edited: Sep 29, 2020
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