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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance in Past Cadillac Vehicle Discussion; Replacing the ECM might have solved the problem before, because the ECM controls/supplies the ground to the cut-off relay (so ...
  1. #16
    sven914 is offline Cadillac Owners Connoisseur
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    Replacing the ECM might have solved the problem before, because the ECM controls/supplies the ground to the cut-off relay (so it can turn off the compressor when there is high engine load). You can cut the ECM out of the system by taking the relay directly to ground, and it will still work and switch on and off as normal.

    The relay is supplied power by the power module when the A/C is set to on, so taking it to grounded won't affect that. The compressor will still cycle correctly because the cycling switch and pressure switch are the clutch's grounds, and remove that ground when open. If it wasn't for the E-carb, the ECM could be completly removed and the car wouldn't function any differently; which is why I'm working on getting rid of the E-carb.

  2. #17
    My_favorite_Brougham's Avatar
    My_favorite_Brougham is offline Cadillac Owners Connoisseur
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    Well I discovered a clutch problem diagnosis section of my service manual so I will check it out. I do have a set of R12 gages and have seen that I have ample freon. I'm thinking either a control module or a compressor relay. We'll see.

    Till then, I have to put up with this until the A/C kicks in!



    And sadly this weather has caused my brand new headliner to begin sagging in the rear.

    -Greg

  3. #18
    sven914 is offline Cadillac Owners Connoisseur
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    Have you tired turning the temperature to 60 and hitting Defrost. That might trick whatever is malfunctioning into giving you "emergency" compressor engagement. I've found the system to be rather stupid and easy to trick, as you can usually use defrost make it forget the warm-up fan delays. It might work the get your compressor clutch to engage earlier.

  4. #19
    My_favorite_Brougham's Avatar
    My_favorite_Brougham is offline Cadillac Owners Connoisseur
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    I have. It doesn't make a difference. I have recently begun experiencing disengagement while driving. It will randomly turn off during long drives for 5-10 minute periods. Then other days it will instantly come on at start up.

  5. #20
    tbcaddy18 is offline Cadillac Owners Fanatic
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    ^^^ I have the exact same issue too

  6. #21
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    Well friends, believe it or not I still have this issue. The good news is I have thoroughly narrowed down the problem using the FSM schematics, and I know for a fact that the problem is the A/C Power Module, also referred to as the A/C Blower Module occasionally.

    I was just putting up with the issue last summer, and winter wasn't really a bother - winters are nice in Texas - but now my blower has completely died. It's not the motor, which I've tested; it just won't engage. All signs point to the power control module. It sits immediately right of the blower motor under the hood, and has two heavy wires: a ground, and a wire to the blower motor. There's also a 6-pin plug where it receives info from the dash controls. (This is oddly similar to the radio head unit and amp setup in these years, too.)

    My dilemma now is finding one. Rockauto has them for about 10x the salvage yard price, but that's a bit steep for me (yes, even in Texas heat). And I'd like a used one. However, none of the yards around me have RWD Cadillacs anymore! What a shame! I think many have been crushed lately unfortunately, and few yards have cars from before 1990.

    That's just a very late update!

    Greg

  7. #22
    csbuckn is online now Cadillac Owners Connoisseur
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    What year cars can you get this part from? Winter in Texas? I came home(Fort Hood) for new years and it was like 75 degrees. Long way from Minnesota. My dad says they have been getting hundred plus days pretty much all summer.

  8. #23
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    Quote Originally Posted by My_favorite_Brougham View Post
    Here's another reason I think why. All Broughams have a feature to disengage the compressor under wide-open-throttle. Well, I can be driving the for a while - and be all comfy chilly - but when I floor it it kills the compressor and doesn't re-engage for another 5 minutes of driving. Under the "cool down" period theory, the system would already be cooled down and not need another 5 minutes.
    Alot of if not all cars do that. At WOT on both my grand am and alero above like 4k, the PCM kills the a/c. But once i take my foot out of it the a/c turns back on. I would start looking for bad connection, and old wiring. What you have going on is not normal. Their is also a resistor on the compressor plug that could be going out..

    Quote Originally Posted by sven914 View Post
    ^That's called cycling. The compressor is supposed to periodically engage and disengage while the A/C is on. It does that to conserve fuel while the air conditioner is on without causing periods of under cooling.

    ummmm nope.
    The system builds up pressure on the liquid line. The compressor shuts down when it gets high. The liquid line pressure drops and the compressor kicks back on. Alot of new cars still do this. My car the compressor does not cycle. I forget what those are called. If i remember our old 84 sedan deville right. On auto 60, it would blow air out the feet first them switch to face. Running on HI would default to face. The only delay i know of is the heater delay, i have that on my 84 Electra Wagon and our deville had it.

    Quote Originally Posted by sven914 View Post
    If it wasn't for the E-carb, the ECM could be completly removed and the car wouldn't function any differently; which is why I'm working on getting rid of the E-carb.
    You forgot the CCC disturber. You remove both. Without the CCC carb the disturber will not advance right. Also without the PCM the trans will not lock up 4th gear.

  9. #24
    My_favorite_Brougham's Avatar
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    I'm in College Station right now, so Fort Hood is not that far away. And yes, we've have 100+ days for the last couple months. We topped out at 109 a few days ago!

    The A/C power module for an '89 Brougham can be had from '86 to '89 Broughams; basically 307 Broughams that are not 90-92. The 90-92 Broughams have a slightly different harness, and so do the HT4100 Broughams. I'm not sure about '81 and before.

    And I have good news. I finally found a power module from a private individual's car lot that I heard of by word of mouth. It all works, even better than before! My fan speed is much better than it ever was. Previously, the "Hi" setting felt like low in any other car, but it blows me away now.

    Greg

  10. #25
    tbcaddy18 is offline Cadillac Owners Fanatic
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    I've been having this same exact issue with my FWB since we purchased her back in 2003. Sometimes turns on, sometimes not....during cruise it'll stay on and cool for a long period of time...then it'll just shut off for a few minutes then come back on.

    I too was thinking it may be the ac power module....is that the part that's sitting on the top back of the engine compartment to the right of the blower fan motor?...is it also referred to as the blower motor resistor?

    Pepboys has them for like $300+....but ive seen them on ebay NOS before for far less..but still pricey...

  11. #26
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Re: It's HOT in Texas, and I have a HOT '89 Brougham d'Elegance

    ^grab one (or a couple) from a junkyard. much cheaper

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