Continuous accessory power drain on '99 DeVille
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Continuous accessory power drain on '99 DeVille in Past Cadillac Vehicle Discussion; HELP! I have a continuous power drain coming from the accessories on my 99 DeVille I recently purchased. After turning ...
  1. #1
    tsimmonsjr is offline Cadillac Owners Member
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    Continuous accessory power drain on '99 DeVille

    HELP! I have a continuous power drain coming from the accessories on my 99 DeVille I recently purchased. After turning off engine, radio/clock/windows etc stay on/will work and creates a slow burn on the battery until it dies.

    It started after two days of rain while on vacation in the Outer Banks. First the alarm kept going off, then in the morning found everything dead. Jump started it, but the clock stayed on after removing the key. Next morning it was dead again. Jump started it again, drove 7hrs to home. Mid way stopped for gas, and the radio turned off with the key. Thought things were fixed.

    1.5-2 weeks later (after no issues) it happened again, again it had rained. Took it to Pepboys, they have no clue. Have checked fuses, replaced accessory time delay relay and inadvert power relay. Can jump start, if I charge up the battery driving around a bit it will sometimes turn off the radio on engine turnoff but later the security alarm goes off again, and the radio/clock stays on.

    Any advice? Guidance? What to check?

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    Ranger's Avatar
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    Re: Continuous accessory power drain on Cadillac '99 DeVille

    Took it to Pepboys, they have no clue.
    Now there's a shocker.

    Pull the negative battery cable abd place a 12v test lamp between the cable and the battery terminal. If you have a draw, the light should illuminate. Now start pulling fusses until it goes out. Then you'll know what component or circuit to concentrate on.

  4. #3
    rodnok01's Avatar
    rodnok01 is offline Cadillac Owners Connoisseur
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    Stock radio?
    Weak batteries cause all kinds of issues in these.
    The BCM turns off power using one of two relays in case one fails.

    sorry missed you already changed the relays. Like Sub has said start checking connections, they are picky about grounds and there are many.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Continuous accessory power drain on Cadillac '99 DeVille

    If the battery is more than 5 years old, start there. Also, the usual battery cable terminal checks - all 4 ends. If your battery is under the back seat, those setups sometimes develop problems with the ground cable body stud. (If the battery IS under the back seat, it's a special vented Group 79 unit. 880 CCA)

  6. #5
    tsimmonsjr2 is offline Cadillac Owners Member
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    Re: Continuous accessory power drain on Cadillac '99 DeVille

    So I think I fixed it last night.

    What I had done up to this point is replace the Accessory Time Delay Relay, as well as the Inadvert Power relay to no avail.
    I also checked fuses, and started pulling relays one by one (both in the trunk relay center and the main relay center up front)

    Finally I started switching/swapping relays. I took the "Accessory relay" and swapped it with the "headlamps" relay (since they use identical part). For some reason, it fixed my problem. The headlamps relay, when placed into the accessory relay slot, fixed the problem.

    When the "bad relay was changed from "accessory" to "headlamps" it didnt cause any new problems. The headlamps still work?? So basically I have a relay that doesn't work properly in the accessory relay slot, but that same relay will work when placed into the headlamps relay slot.

    Any thoughts on this? What does the headlamp relay do? Could that relay be bad, and the headlamps still work?

    Thanks so much

  7. #6
    SUPER LAC DEVILLE's Avatar
    SUPER LAC DEVILLE is offline Cadillac Owners Enthusiast
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    Aftermarket Radio ?

    These Deville's are finicky about those things

    I always ask this question first bc people buy these cars and that's the first thing they alter

    Sometimes it's an immediate problem or it could take months to years to start electrical problems...

    Caused by poor installation and a complete lack of understanding that these Cadillacs aren't your average Chevy Vega


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    rodnok01's Avatar
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    Re: Continuous accessory power drain on Cadillac '99 DeVille

    Bad connection or flaky relay.

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    Re: Continuous accessory power drain on '99 DeVille

    1999 car, 14+ years old. Perhaps the simple act of removing the relay(s) wiped a tad of corrosion off the relay blades or socket contacts.

    For a mindless exercise, pull/insert ALL the fuses and relays one by one.

  10. #9
    tsimmonsjr2 is offline Cadillac Owners Member
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    Re: Continuous accessory power drain on '99 DeVille

    Hi, No aftermarket radio. Standard cd/tape player combo.

    The latest development is the accessory relay melted, causing the accessory relay and the one below it (headlamps relay) to mold together. I removed those two (now damaged) relays, so now I have no headlights or wipers, because both the accessory and headlamp relays are now out of the car, after haven been melted.

    What causes a relay to melt?
    What is the part called that the relays plug into?

    Thanks guys, absolutely love my car but geez.... I hate when she is sick

    Here are some photos
    pic1.jpgpic2.jpgpic3.jpgpic4.jpg
    Attached Images

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    rodnok01's Avatar
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    Poor / corroded connections cause overheating. A loose connection that allows movement even a slight bit will cause arcing and melt them also

  12. #11
    tsimmonsjr2 is offline Cadillac Owners Member
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    Re: Continuous accessory power drain on '99 DeVille

    All of the relays are loose, any way to fix this? all of the relays in that "relay center' are loose (headlamps, accessory, daytime running lights, horn)

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    SUPER LAC DEVILLE's Avatar
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    Quote Originally Posted by tsimmonsjr2 View Post
    All of the relays are loose, any way to fix this? all of the relays in that "relay center' are loose (headlamps, accessory, daytime running lights, horn)
    Buy New Ones




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    Quote Originally Posted by tsimmonsjr2
    All of the relays are loose, any way to fix this? all of the relays in that "relay center' are loose (headlamps, accessory, daytime running lights, horn)
    The posts are loose in the relays, or the relays fit loosely in the sockets?

  15. #14
    tsimmonsjr2 is offline Cadillac Owners Member
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    Re: Continuous accessory power drain on '99 DeVille

    Bump

    Looks isolated to comfort fuse, when I pull the comfort fuse, battery doesn't drain. hearing constant "hissing" from speakers with key off, this too is eliminated by pulling the comfort fuse

    Does anyone know how to

    1) unhook power to the cell phone (which is analog and is useless these days anyway)
    2) unhook the amplifier, but hopefully so that I could still have radio, just not amplified? (when i pull the connector out of the amplifier I don't have any sound

    the reason i ask about these is I have seen a lot of people with drains on the comfort fuse which were ultimately traced to the cell phone and/or the amp in the trunk

    thanks

  16. #15
    rodnok01's Avatar
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    The cell phone should have a plug you an just unhook it.
    As for the amp no easy way around it, better off trying to find a used one. I would unhook both & drive for a coupple weeks with fuse back in to see if it works before you chuck money at it.

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