2000 Mustang A/C Issues...Help!!!

Discussion in 'SN95 V6 Mustang Tech' started by Nelly007, Jul 19, 2011.


  1. Nelly007

    Nelly007 New Member

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    I have recently been having issues where the a/c clutch will not engage, so I am getting hot air blown into the cabin. I have tested a number of things, but at this point i am having trouble stiching together the information on various forums to find a way to continue, so here is the run-down:

    -All fuses are good and tested

    -There is an adequate refrigerant charge (100 psi static, 40 when the clutch has been working** more on this below)

    -The low pressure switch is working fine. 12v at the harness and when the clutch is jumped, everything works here.

    - There is no power being supplied to the compressor clutch (circled in orange). The clutch, however, does engage, spin and blow cold air when jumped to the battery.

    -12v at the high pressure switch (circled in yellow, gr/o lead-think miami colors) when the ac switch is engaged

    That is all I have tested. I imagine the CCRM is behind the panel where the blue arrow points. What is the relay circle in purple? WOT? What else must I test before replacing the CCRM?

    **last week the problem of the a/c clutch not engaging only occurred in the afternoons. Once the sun went down, and the car would sit (usually through a 3-hour night class or when i woke up in the morning), the a/c would work fine. just last night, however, it stopped working all together and hasnt resumed functioning.

    [​IMG]

    Where do i need to go from here? any help would be appreciated
    #1
  2. wmburns

    wmburns SN Certified Technician

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    how to trouble shoot CCRM V6 1999-2004

    Help is here. Note, there are wiring differences between the V6 and V8 AC systems.

    Confirm the A/C pressure (20a) in the battery junction box.

    Also confirm fuse F2.2, F2.24, and F2.23 in the central junction box. Confirm means more that just "look at it".

    Are there any other DTC codes? There are some DTC codes that disable the AC (overheating is one).

    Measure the resistance of the AC clutch black wire back to battery negative (key off). Should be low. Post. If not, STOP and find out why.

    Confirm there is +12 volts with the AC and key on to the high pressure switch DG/OG wire. If no voltage, STOP and recheck your work because there's a problem in the wiring before the High pressure switch.

    Go to the CCRM. Easier to access with the plastic fender liner removed.

    Measure the resistance from CCRM pin#15 (BK/WH) back to battery negative with the key off. Post. Should be low. If not, check for bad grounds at the CCRM and battery.

    Test CCRM pin #21 (DG/OG) for +12 volts. If no power, you failed because AC pressure fuse is bad.

    Test CCRM pin#12 (RD) for +12 volts with the key on. If no voltage, you failed because fuse F2.2 is bad or there's a wiring fault.

    Use an ODB2 scanner to find out if the PCM is calling for AC. If not, then this offers an explaination why the AC clutch won't engage.

    With the key on, ground CCRM Pin#22 (PK/YE) to a known good ground. Does the AC clutch engage?

    If not, since the AC clutch has already been tested OK, then replace the CCRM.

    If the clutch does engage, then the CCRM is working as it should. Likely there is a wiring fault to the PCM or the PCM is bad.

    If the CCRM needs replacement, recommend a re-man unit from your local autoparts store.

    >>
    Onto your questions.

    The purple thing is a body harness connector. No active parts.

    The CCRM is at the end of the blue arrow. Good work.

    The yellow circle is the high pressure switch. Good job.
    #2
  3. Nelly007

    Nelly007 New Member

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    Troubleshooting begun...

    Confirm the A/C pressure (20a) in the battery junction box.
    --Confirmed (Just measured the voltage (12), If I understand correctly, this is easier and faster to test voltage from each lead on top than pulling and measuring resistance, if not, let me know)

    Also confirm fuse F2.2, F2.24, and F2.23 in the central junction box.
    --Confirmed

    Are there any other DTC codes? There are some DTC codes that disable the AC (overheating is one).
    --Forgive me, I have no idea what this is. My previous experience only involves wiring new speakers/radios and a headlight
    ***Edit*** I have not hooked up an OBD-II computer to check for any codes yet as I do not have the equipment. Will run to autozone tomorrow and have it done first thing.

    Measure the resistance of the AC clutch black wire back to battery negative (key off). Should be low. Post. If not, STOP and find out why.
    --4.9-5.0 ohms. I assume this is low enough, as when I unlock the car (thus turning on interior lights) it jumps to 50.

    Confirm there is +12 volts with the AC and key on to the high pressure switch DG/OG wire. If no voltage, STOP and recheck your work because there's a problem in the wiring before the High pressure switch.

    --Second glaring lack of knowledge is evident here. When connecting the the negative lead of the multimeter to the DG/Orange wire and positive to the Blue/white I read 11.65V. I did this as electricity flows from negative to positive and I understood from other forum posts that the DG/OG supplies the power to the a/c clutch. Obviously, when reversed, the reading is -11.5V.

    I also ran it Positive lead (on multimeter) to DG/OG, negative multimeter lead to negative battery terminal for a reading of 168mV, merely to be thorough, but I do not believe that method is correct.


    Tonight I cannot go into testing the leads at the CCRM as I posted just before getting to my evening classes and now, at 11pm I am too tired and the light is too low, but I believe so far with your help I have confirmed my original methods. I will be back at it, with the results bright and early and appreciate not only your help, but your patience.
    #3
  4. wmburns

    wmburns SN Certified Technician

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    To confirm +12 volts at a sensor, put the negative lead on a known good ground. Put the red lead on the sensor to be tested.

    Since you stated measuring less than one volt on the high pressure DG/OG wire, THIS is why the AC isn't engaging.

    Test for +12 volts at the high pressure switch DB/YE, If power into the high pressure switch but no power out, the switch is bad.

    Test for +12 volts at the LOW pressure switch VT wire. If no power, the problem is in the AC controller inside the dash.

    If voltage, test for +12 volts out of the low pressure switch (DB/YE). If no power, the low pressure switch is bad.

    NOTE, 4-5 Ohms of resistance for a ground circuit is very marginal to too high. Look at the quality of the grounding connections.
    #4
  5. Nelly007

    Nelly007 New Member

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    Since you stated measuring less than one volt on the high pressure DG/OG wire, THIS is why the AC isn't engaging.
    --was tired last night and must have had a bad connection...measured 12v

    Test for +12 volts at the high pressure switch DB/YE, If power into the high pressure switch but no power out, the switch is bad.
    --Confimed, 12V

    Test for +12 volts at the LOW pressure switch VT wire. If no power, the problem is in the AC controller inside the dash.
    --confirmed 12V

    If voltage, test for +12 volts out of the low pressure switch (DB/YE). If no power, the low pressure switch is bad.
    --confirmed 12v

    Now moving on to testing the CCRM as explained last night after a quick snack. will post results
    #5
  6. Nelly007

    Nelly007 New Member

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    Measure the resistance from CCRM pin#15 (BK/WH) back to battery negative with the key off. Post. Should be low. If not, check for bad grounds at the CCRM and battery.
    --1.9 ohms

    Test CCRM pin #21 (DG/OG) for +12 volts. If no power, you failed because AC pressure fuse is bad.
    --confirmed 12V

    Test CCRM pin#12 (RD) for +12 volts with the key on. If no voltage, you failed because fuse F2.2 is bad or there's a wiring fault.
    --confirmed

    Use an ODB2 scanner to find out if the PCM is calling for AC. If not, then this offers an explaination why the AC clutch won't engage. will do shortly

    With the key on, ground CCRM Pin#22 (PK/YE) to a known good ground. Does the AC clutch engage?
    ---No engage. Grinding clicking noise at ccrm but no a/c clutch movement.
    Is this the problem? new CCRM?

    If not, since the AC clutch has already been tested OK, then replace the CCRM.

    ---retested the resistance from the a/c clutch black wire to battery terminal. 2 ohms. sat. radio was plugged in last time. my mistake
    #6
  7. Nelly007

    Nelly007 New Member

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    Just had an ODB2 scan at the local auto parts store and got no codes. May be inconclusive, however, as I had disconnected the battery a week ago to turn off the check engine light so I could pass state inspection. The check engine light had previously given a code for low gas cap pressure, so all I had to do was get out of the parish that requires the gas cap check. Battery has been connected since then with quite a while of driving, and as I said, no codes at the local store. Just want to confirm that when the one lead (PK/YE) was grounded and the clutch did not engage it is a ccrm issue before I order it. Again, many thanks.
    #7
  8. wmburns

    wmburns SN Certified Technician

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    I personally would not spend over a $100 bucks on a part until the ground tests are done. I would also want to know why there's no power coming out of the the high pressure switch before spending real $$.

    But that's just me. Test first. Replace what's broken. Don't guess.
    #8
  9. Nelly007

    Nelly007 New Member

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    Sorry if you check my posts I got 12v out of bOth sides of the high pressure switch. I was careless last night but have checked at least 5 times today and there is power on both sides of the high pressure switch
    #9
  10. Nelly007

    Nelly007 New Member

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    which ground test?
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  11. Nelly007

    Nelly007 New Member

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    Crossed signals

    I believe we are getting our messages mixed up and I take responsibility as the posts from my phone are not as well-organized as the posts from my computer and, for that, I apoligize. To get back on track I will consolidate your requests and the results of my tests in this post.
    *******************************************************

    Confirm the A/C pressure (20a) in the battery junction box.
    --confirmed

    Also confirm fuse F2.2, F2.24, and F2.23 in the central junction box. Confirm means more that just "look at it".
    --confirmed

    Are there any other DTC codes? There are some DTC codes that disable the AC (overheating is one).
    --no codes

    Measure the resistance of the AC clutch black wire back to battery negative (key off). Should be low. Post. If not, STOP and find out why.
    --1.9 ohms

    Confirm there is +12 volts with the AC and key on to the high pressure switch DG/OG wire. If no voltage, STOP and recheck your work because there's a problem in the wiring before the High pressure switch.
    --confirmed 12v

    Test for +12 volts at the high pressure switch DB/YE, If power into the high pressure switch but no power out, the switch is bad.
    -- confirmed 12v

    Test for +12 volts at the LOW pressure switch VT wire. If no power, the problem is in the AC controller inside the dash.
    --confirmed 12v

    If voltage, test for +12 volts out of the low pressure switch (DB/YE). If no power, the low pressure switch is bad.
    --confirmed 12v

    Go to the CCRM. Easier to access with the plastic fender liner removed.

    Measure the resistance from CCRM pin#15 (BK/WH) back to battery negative with the key off. Post. Should be low. If not, check for bad grounds at the CCRM and battery.
    --1.4 ohms

    Test CCRM pin #21 (DG/OG) for +12 volts. If no power, you failed because AC pressure fuse is bad.
    --confirmed 12v

    Test CCRM pin#12 (RD) for +12 volts with the key on. If no voltage, you failed because fuse F2.2 is bad or there's a wiring fault.
    -confirmed 12v

    Use an ODB2 scanner to find out if the PCM is calling for AC. If not, then this offers an explaination why the AC clutch won't engage.
    --no codes

    With the key on, ground CCRM Pin#22 (PK/YE) to a known good ground. Does the AC clutch engage?
    -- the CCRM emits a click when contact is made, but no a/c clutch movement

    If not, since the AC clutch has already been tested OK, then replace the CCRM.
    --a/c clutch re-tested: OK

    All of these tests were re-run in the last 45 mins to ensure accuracy. Sorry for the earlier confusion, but my methodology that first night was bad and thus the accuracy of the tests suffered. This is my mistake. Any other tests, or can we confirm a bad CCRM?

    Thank you for sticking with me. I agree it is better to test multiple times before throwing money at it, especially as I have such little money to spare. Please review the info and I appreciate your continued guidance and patience.
    #11
  12. wmburns

    wmburns SN Certified Technician

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    I wish more ppl would take the time to do the test and communicate the results. Much easier to solve problems this way.

    Since you hear the CCRM relay click but nothing happens AND all of the needed inputs are present at the CCRM, I agree with the diagnosis. Bad CCRM.

    Recommend getting a re-man unit from your local autoparts store. Will be able to get your $$'s back if there's a problem.

    If you are good with a soldering iron, it might be possible to replace the PC board relay. Or you may find burnt PC traces upon visual inspection. If so, it may be possible to repair it yourself.

    Good luck.
    #12
  13. Nelly007

    Nelly007 New Member

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    Results!

    While I am proficient with a soldering iron, I do not have the workspace of my dad's garage, so I ordered the re-man CCRM.

    Part came in this morning, but before installing I did a continuity check the BLK/Y wire from the old CCRM to the A/C clutch to make sure that there wasn't a break that was causing the issue. All checked out, so I installed the CCRM.

    Feels like the top of Mt. Everest. With your help, I was able to fix the issue for less than $100. The local dealerships were charging $240 for just the CCRM and labor was estimated at another $250.

    I have no way to express my gratitude for the assistance and patience you have given me. If you ever come through the BR area, i'll buy you some drinks.

    Thank you, and GEAUX TIGERS!
    #13
  14. jstreet0204

    jstreet0204 Active Member

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    Just wanted to say thanks to wmburns as well. I came across this thread while try to diagnose the exact issue in my 99 GT. Wiring is a little different from the v6 models, but your detailed diagnostics steps saved me a huge amount of time and probably money. Tracked it down to a bad CCRM as well, replaced it with a reman unit from napa, and I have cold air once again. The heat here has been miserable. The worst time to lose my AC in my car. Thanks again.
    #14
  15. Nelly007

    Nelly007 New Member

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    This thread should be stickied/archived for future use. The knowledge of wmburns is too great to get buried anywhere
    #15
  16. wmburns

    wmburns SN Certified Technician

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    Thanks for the kind words.

    Just in case you are interested, I have a secret. Over the years I have a put together a fairly complete library of Ford service DVD's from 1990 through 2011. It's amazing how much smarter it makes one seam when that much information is at your fingertips.

    Modern computers are amazing.

    It also helps when the practical experience is added to the mix.

    It has taken time and $$ to put the collections together. So any/all appreciation is welcome. :D
    #16
  17. 04V6Stang

    04V6Stang Member

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    Very informative thread. Now, I hope you can help me out Mr. Burns! I am have the exact same problem. Pulled the AC fuse in the box near the battery and checked with the VOM, good. Pulled the three fuses that you listed as F2.2, 2.24 and 2.23 in the fuse block up under the dash, all good. I assume that these are numbers 2, 23 and 24? Applied 12 volts to the compressor and it will run, plenty of charge in the system, just quit working the other day without warning.

    Now on to the rest of the checks. I went in order with everything checking out as you described until I got to pin #12(RD) on the CCRM - no voltage. Fuse was good, assuming that it is powered by one of the three fuses in the under dash fuse block. One question I have is that I was measuring the voltage, key on, negative lead of the VOM hooked to the battery, but the high pressure switch and the lead to the compressor were both unplugged. Would that have affected the circuit?

    If not, then is there a break somewhere in the wire or a problem with the AC controller inside the dash.

    One other question: you discussed earlier in the thread about checking 12 volts in and out of the high and low pressure switches. When I checked the high pressure switch, I get nothing from the DG/OG wire, but I do get 12 volts from the BL/YL wire, any suggestions?

    When checking voltage out of the switches, are you suppose to jumper the connector to one side of the switch and check the voltage on the opposite pin of the switch? Thanks in advance for any help, it will be another day in the 90's tomorrow down here and I sure would like to get this figured out asap.
    #17
  18. wmburns

    wmburns SN Certified Technician

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    For those following on this thread, confirm +12 volts means to place the black lead on a known good ground. Battery negative is best.

    Place the RED VOM lead on the terminal to test. Read the voltage on the VOM meter.

    When testing to see if a switch is good, testing the INPUT to the swich confirms there is power for the switch to pass on. After all, if there isn't power into the switch, then the switch can't pass it along.

    Regarding the question about the fuses. The fuse number is correct. I'm afraid that there is some confusion about WHERE the fuse is located. Look at the fuse numbering.

    F1=BJB=Battery Junction Box-located engine bay.
    F2=CJB=Central Junction Box-located driver's kick panel.

    So F1.24 is located in the engine bay.

    Testing for power OUT of the switch, confirms if the switch is actually doing it's job. This either rules in or out the switch as the source of the probelm.

    Testing across a switch with both leads of the VOM is not the correct way to perform the test.

    And yes, unplugging a switch WILL affect the results of any down stream tests thus rendering the test useless.

    FWIIW, the test for CCRM pin#12 (RD) wire has to be done with the key on. With the key off, it will always read zero. The RD wire is feed from fuse F2.2. So if there is no power to the red wire, go back and check your work.

    FWIIW2, I doubt the test results. Why? Because fuse F2.2 also powers many of the motor's sensors. So any problem in this circuit would affect far more than just the AC. If it does prove there is no power to CCRM pin#12 and the fuse is good, with power going in and out of the fuse, then this indicates a wiring FAULT. This will require much harder wiring trouble shooting.

    I suggest that you repeat the measurements paying attention to key off/on state and where the black leads need to be (battery negative). let's see where this takes us.

    Good luck.
    #18
  19. 04V6Stang

    04V6Stang Member

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    OK, went back and double checked my test. With only the CCRM removed, VOM negative to battery, VOM positive lead to CCRM pin #12, key on, NO voltage. There is 12 volts to pin #3,4,8,10,11,13 & 21 with key on. Checked fuse 2.2 which is good, but when I checked voltage to the fuse itself, NO voltage with key on. So, that is where I will start tomorrow, pull the fuse panel and check the wiring connection and trace the wires back to hopefully find the fault.
    #19
  20. wmburns

    wmburns SN Certified Technician

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    Dude...this is really a F'ed up test thread. Please re-read the instructions. No where does it state to remove the CCRM.

    Fuse F2.2 gets it's power from the CCRM. So that would explain why F2.2 has suddenly lost power on a car that otherwise works. Hence the reason for the note about unplugging the switch affecting the downstream results.

    The tests are to be done with the CCRM installed. It would have never occured to me to mention that as a requirement of the test.

    At this point, we should consider all of your tests invalid because I'm completely unsure HOW the tests were performed.

    A VOM is a tool. As a tool, it's usefulness depends to a great deal on the experience of the operator. Electrical issues can be a real PIA. The typical troubleshooting methods involve performing tests. Based upon the results, additional tests are performed. A bogus test result can set up a "wild goose chase" of epic proporations. You sir may have just been saved a great deal of wasted effort.
    #20

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