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Thread: [02 MGM LS] A/C takes time to kick in

  1. #1
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    Angry [02 MGM LS] A/C takes time to kick in

    Gentlemen, what am I looking at here?

    The A/C (I got EATC) takes its sweet time to kick in. I think I'd need to check the refrigerant pressure, but it seems to be OK, because when it does kick in, the air blows hella cold.

    The symptoms to clear things up:
    1. EATC works, save for the dead backlighting. It can randomly switch between Celsius and Fahrenheit.
    2. The vent diverter flaps work, reach every direction as commanded (floor, vents, windshield, closed cycle).
    3. When turned on, the A/C will not blow for a long time. Note this: IT DOES NOT blow hot air from the heater core, it blows fresh air when running in any mode other than Max A/C (in the latter case, it will recycle the cabin air).
    4. After a longer time, it starts blowing freezing cold air - as it should when the interior is hot.

    I tested it today in these conditions:
    Outdoor temp 64 F, cabin temp 72 F (the car sat in the sun). Wouldn't blow cold air from the A/C, just the cooler air from the outside (and recycle air in Max A/C). After 3-4 minutes of driving and fiddling with the EATC controls (blower speed, vent selection, Max A/C, turning it off and on again) I left in Max A/C, only then did it start blowing cold A/C air (after 1 more minute or so). When it blows cold air, it's hella cold, so I think the A/C charge is OK. The temp sensors read from the PCM read OK.

    Day two of testing:

    Outside temp 76 F, cabin at just about the same, fired her up first time this day.
    The A/C compressor took 10 minutes (!) to kick in; then it was blowing hella cold air, so I guess there's no coolant leak.
    Left the car for 10 mins on a parking lot, went back, fired it up, the same happened. This time it took the A/C compressor 2-3 minutes to kick in.
    Each time it happened I was switching between Max A/C, Normal A/C, and Auto, to no effect, until the compressor "felt like it".

    Ran the EATC self diagnostic routine, no codes.

    Day three:

    Took a feeler gauge to the clutch plate on the A/C compressor. Read ~0.3-3.5 mm at every 120 deg. point around the circle, and the service manual says the gap setting should be within 0.35-0.75 mm, so I guess it's OK.

    I'm now leaning to an electrical control issue. It's like something is not commanding to energize the A/C compressor clutch magnet to run, as if there was a feedback missing from one of the sensors in the A/C system or the EATC isn't running the compressor until it does.

    Given that my EATC has developed a 'homesick syndrome' (switching from Celsius to Fahrenheit by itself), should I suspect that there's a PCB solder going bad in it and POSSIBLY causing this compressor run delay? As in, the EATC needs to stay tickled with power until it starts responding to what the A/C system sensors tell it and turn on the compressor?

    And if not, what sensor outputs EXACTLY make the EATC resolve that the A/C compressor should run or not? I'll repeat - the A/C kicks in when the compressor is 'told' to kick in, and it is told with a HUGE delay - like, 10 minutes of driving at 80 F outside and 80-85 F in the cabin, when I start the car that sat for hours in the sun (and in this case the EATC blows air into the cabin, just without the A/C until the compressor kicks in).
    '00 Mercury Grand Marquis LS, Silver Frost, the "Sharona": runs, drives and currently with mods in progress
    '96 Chrysler Grand Voyager LE 3.3 V6
    "You obviously have not been introduced to the ASTM Guidance for Profanity Gauging of Technical Services, Addendum#1, American English to Polish Scale Conversion, by which a repair done at a rate of 35 kurwas per 5 minutes means normal performance."

  2. #2
    I'm an air-conditioned gypsy gadget73's Avatar
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    I know some of the EATC units had an issue with a relay on the board that powers the AC compressor. The solder would crack and it wouldn't feed power out. Apparently they were fixable if you open it up and re-solder the thing.

    http://www.lincolnsonline.com/tech/00261.html

    No idea if that still applies by 2002 but its worth a look.

    The other clue this is the problem is you will not see +12v at the AC low pressure switch on the side of the drier. If you can back probe the connector you can verify if power is coming out of the EATC unit or not.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  3. #3
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    You know, it might actually be that.
    Today I kinda forced the sucker to start the compressor by repeatedly cycling between Max A/C, Normal A/C, Auto, and switching over between Fahrenheit and Celsius (by pressing the two outboard buttons on the EATC).

    Say that I would pull the EATC - any specifics on replacing other components aside from the vacuum o-rings?
    '00 Mercury Grand Marquis LS, Silver Frost, the "Sharona": runs, drives and currently with mods in progress
    '96 Chrysler Grand Voyager LE 3.3 V6
    "You obviously have not been introduced to the ASTM Guidance for Profanity Gauging of Technical Services, Addendum#1, American English to Polish Scale Conversion, by which a repair done at a rate of 35 kurwas per 5 minutes means normal performance."

  4. #4
    I'm an air-conditioned gypsy gadget73's Avatar
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    thats usually the only thing that goes. I've had my hands in one of those units before and there isn't exactly much that is user-serviceable inside. The lamps are even soldered in. Beyond the vacuum valves and a couple relays its basically just chips on a board. If the buttons are flaky maybe give them a clean. I don't quite remember if its a rubber membrane that touches a trace on the board or an actual switch button soldered on. If it shows evidence of cap leakage those can probably get replaced but I don't remember there being very many inside.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  5. #5
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    Alright, thanks!

    This might be a good time to resolder new backlighting bulbs into the EATC. All of mine died a long time ago... I got the funky EATC bulb that's half a step between the old wedge-lock bulbs and those soldered ones that sit in round bases of some sort, the bulb bases/holders on mine are rectangular (I already inspected the guts some time ago). I hate taking a soldering iron to any PCB, but a friend I got does this for a living, so this base is covered. That box with assorted sizes of o-rings is gonna be handy too.

    "I would do anything for love—"
    Girflfried chorus: STOP BUYING CAR PARTS!
    "—but I won't do THAT!"

    Will update this thread as things go.
    '00 Mercury Grand Marquis LS, Silver Frost, the "Sharona": runs, drives and currently with mods in progress
    '96 Chrysler Grand Voyager LE 3.3 V6
    "You obviously have not been introduced to the ASTM Guidance for Profanity Gauging of Technical Services, Addendum#1, American English to Polish Scale Conversion, by which a repair done at a rate of 35 kurwas per 5 minutes means normal performance."

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