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Thread: Air Conditioning Troubleshooting

  1. #1
    Join Date
    Aug 2010
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    Orange Ca
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    Air Conditioning Troubleshooting

    1995 SWB

    Here's the situation:

    - AC compressor clutch is not engaging
    - System has a full charge of refrigerant (no leaks)
    - Aux fans on all the time regardless of AC control switch position (Is this normal?)
    - Blower motor operates normal
    - No power at clutch connector

    Couple questions:

    - Where exactly is the AC clutch relay?
    - Is the AC system controlled through the ECU? If so, what pin(s) can be checked for voltage?
    - Is there a way to check the dual pressure switch?

    I tried searching this forum for information but was unsuccessful. If there is a thread that already addresses this please share the link.

    Appreciate any and all information that is provided.
    1995 RRC SWB
    2005 LR3 G4 Challenge
    2012 Mustang BOSS 302 Laguna Seca
    1965 Mustang 289 4spd
    1963 Jeep Wagoneer

  2. #2
    Join Date
    Oct 2007
    Location
    Kelseyville, Ca.
    Posts
    2,408
    I can answer some of your questions. First, no, the aux fans are supposed to come on only when the A/C power button is pressed and the fan switch is turned on, or when the engine temp exceeds 212.

    I assume you don't have the '95 RRC Electrical Troubleshooting Manual, virtually all of your questions are covered in there. Section K2, Compressor, is what you want. Here's a link to the manual in pdf form:

    http://www.landy.ee/manuals/electric...HBEMENL95).pdf

    Be sure to read through the Introduction section, it makes deciphering the schematics much easier. There's a ton of info in there such as wire harness connector locations, relay locations, wire colors of course, and more, as well as step-by-step troubleshooting procedures. But it can be a little bit of work to find some of that info, as is common with automotive manuals written in England.

    Section Z4 lists all components and their locations. The compressor clutch relay is K108 and is located behind the passenger side kick panel. There are illustrations near the end of the manual in section Z4 that show each of the components and exactly where they are, the one for the clutch relay is #143, pg. 651 of the manual.

    And yes, the ECU does control the A/C system, it's explained in the ETM.
    Last edited by TigerDan; 07-25-2017 at 09:14 AM.
    '91 RRC-4.2, R380, LT230, GDE bumper with Smittybuilt 8K winch, Custom 3" lift, 33's, Equipe trailing arms, Rock Ware sliders, Custom diff guards, Maxyedor HD steering, TT/Detroit, Rovertracks axles
    '61 Series II 88"
    '95 D90
    '94 RRC County LWB

    "There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves." -Will Rogers

  3. #3
    Join Date
    Aug 2010
    Location
    Orange Ca
    Posts
    215
    I found a copy of the ETM on my computer last night and was able to start troubleshooting. The aux fan temp switch is definitely faulty. The resistance through the contacts stays the same regardless of coolant temp. I ordered a replacement today. The dual pressure switch isn't the problem, clutch doesn't engage when jumped. I started to look at the relays in the passenger footwell but didn't get too far, however, I went far enough to unplug something that is keeping the engine from firing. (oops)

    The plan is try some more tonight.

    Hopefully good news will be reported in the morning.
    1995 RRC SWB
    2005 LR3 G4 Challenge
    2012 Mustang BOSS 302 Laguna Seca
    1965 Mustang 289 4spd
    1963 Jeep Wagoneer

  4. #4
    Join Date
    Oct 2007
    Location
    Kelseyville, Ca.
    Posts
    2,408
    So you're saying that you jumped the compressor at the relay, or directly at the compressor? I'd jump it at the compressor just to check the clutch itself.
    '91 RRC-4.2, R380, LT230, GDE bumper with Smittybuilt 8K winch, Custom 3" lift, 33's, Equipe trailing arms, Rock Ware sliders, Custom diff guards, Maxyedor HD steering, TT/Detroit, Rovertracks axles
    '61 Series II 88"
    '95 D90
    '94 RRC County LWB

    "There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves." -Will Rogers

  5. #5
    Join Date
    Aug 2010
    Location
    Orange Ca
    Posts
    215
    No, the wording in that sentence isn't very good. I jumped the pressure sensor with the truck running and the clutch did not engage. That leads me to think the sensor isn't the issue.

    I should jump the clutch to see if it's operational.
    1995 RRC SWB
    2005 LR3 G4 Challenge
    2012 Mustang BOSS 302 Laguna Seca
    1965 Mustang 289 4spd
    1963 Jeep Wagoneer

  6. #6
    Join Date
    Aug 2010
    Location
    Orange Ca
    Posts
    215
    Followed the ETM troubleshooting steps for compressor clutch control circuit and did not get too far. When it asked me to bridge terminals 30 and 87 in the AC relay connector I did not get the result that would allow me to move forward. Bridging those two terminals should have operated the clutch. Since this did not happen I proceeded to confirm the clutch operates by jumping it directly from the battery, it does operate. I traced the harness from the connector to the compressor and did not find any connectors or obvious damage. I'll need to unwrap the harness to investigate further.

    Whats the best way to test the AC switch in the dash? Most of my dash doesn't light up any more including the AC switch. There's no indication it's working at all. How hard is it to get the center dash stack out to replace all the bulbs and troubleshoot the switches?
    1995 RRC SWB
    2005 LR3 G4 Challenge
    2012 Mustang BOSS 302 Laguna Seca
    1965 Mustang 289 4spd
    1963 Jeep Wagoneer

  7. #7
    Join Date
    Oct 2007
    Location
    Kelseyville, Ca.
    Posts
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    It's not too bad, actually. Pull the three round control knobs off (sometimes you can pull them off by hand, I've also had to use pliers with the jaws padded with electrical tape) as well as the fan control switch. Underneath you'll see the screws that hold the wood fascia in place, remove them and pull off the fascia and you'll then see the 4 screws in the corners of the control unit that hold it to the center dash section. Be very careful removing these as the tabs in the center dash section that the screws go into are easily broken off, don't apply any pressure to the screwdriver except for the bare minimum needed to hold it to the screw heads, and don't force anything. The center dash section is '95 RRC only and is unobtanium. It looks like a Disco unit, but it's just different enough not to be interchangeable. JB Plastic Weld works well for repairing cracks and breaks.

    Ease the center control unit out and you can then get to the clips which hold the control cables, and the connectors on the back of the switches. There's one bulb which lights up the control unit through plastic optics, and the buttons have their own bulbs or LEDs.

    For the 6 control buttons on the left side, each one will pull out of the dash panel fairly easily, it can just be a little tough to get a grip on them. If the air suspension control panel directly under them is still in place, just reach under the bottom of it and pull it straight out, then you have room to get your fingertips under the bottom row of buttons, and once they're pulled out you can get to the top row the same way.
    '91 RRC-4.2, R380, LT230, GDE bumper with Smittybuilt 8K winch, Custom 3" lift, 33's, Equipe trailing arms, Rock Ware sliders, Custom diff guards, Maxyedor HD steering, TT/Detroit, Rovertracks axles
    '61 Series II 88"
    '95 D90
    '94 RRC County LWB

    "There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves." -Will Rogers

  8. #8
    Join Date
    Aug 2010
    Location
    Orange Ca
    Posts
    215
    Great info! Thank you

    I'll report my findings.
    1995 RRC SWB
    2005 LR3 G4 Challenge
    2012 Mustang BOSS 302 Laguna Seca
    1965 Mustang 289 4spd
    1963 Jeep Wagoneer

  9. #9
    Join Date
    Aug 2010
    Location
    Orange Ca
    Posts
    215
    Well, it has come to my attention that I have been looking at the wrong set of relays. By misinterpreting the wire color codes I was attempting to troubleshoot the fuel pump circuit.

    Classic noob move. Now that I know what I'm looking at, I have progressed through the ETM and now need to test the output from the ECU. Contorting myself to see the back of the ECU connector is going to be fun. Is it common for this circuit in the ECU to fail? Can an ECU be repaired? Hoping to have more information tomorrow.
    1995 RRC SWB
    2005 LR3 G4 Challenge
    2012 Mustang BOSS 302 Laguna Seca
    1965 Mustang 289 4spd
    1963 Jeep Wagoneer

  10. #10
    Join Date
    Aug 2010
    Location
    Orange Ca
    Posts
    215
    Looks like I have a bad AC switch and will require removal of the center dash to fix. Fun times.....
    1995 RRC SWB
    2005 LR3 G4 Challenge
    2012 Mustang BOSS 302 Laguna Seca
    1965 Mustang 289 4spd
    1963 Jeep Wagoneer

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