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Thread: 1989 735i battery drain

  1. #1
    Join Date
    May 2010
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    My Cars
    1989 735i date 9/88

    1989 735i battery drain

    Trying to find a greater than normal battery drain. I placed an amp meter between the battery positive and the positive cable I get . 260 amps until I pull the #23 fuse at which point the amp draw drops significantly. My research show this fuse to be a fuel pump fuse for some models and DME/EML supply for others. Schematics I have found are not very helpful, nor is my shop manual which covers 1970 to 88 models (I couldn't find one for the 89 models). Can anyone help me diagnose this drain?

  2. #2
    Join Date
    Jan 2005
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    Japan
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    11/88 E32 750iL+98 E36M3
    which built month? Pls add that to your profile. 1987 - 1994 wiring diagrams E32 are here https://shark.armchair.mb.ca/~dave/BMW/e32/
    fuse no. 23 in model from 9/88 - 5/89 is for injection electronics/DME 1.3, also fuse 17 is connected, 17 has a lot of items.
    also check here https://www.bimmer-service.com/bmw-7-e32/

    Maximum closed current by vehicle E31 50mA, E32 50mA, E34 40mA,E36 30mA,E38 50mA,E39 40mA,E46 40mA,E52 50mA, E53 40mA, Z3 30mA
    Performing Closed Current Draw Test
    • Select proper measuring device (DISplus, MoDic or DVOM). Remember amperage draw in excess of 10A will damage DVOM. Use inductive amp probe of DISplus when amperage draw is high. When using DISplus inductive probe, clamp on negative battery cable with arrow pointing away from battery. Switch off all consumers. (It is not necessary to disconnect B- from body when using inductive probe)
    • Connect (-) test lead to negative battery terminal and (+) test lead to a known good ground.
    • Ensure all systems are OFF !
    • Be sure DVOM is on and set in proper mode.
    • Disconnect battery ground lead from body.
    • Observe meter reading, wait 16 minutes for vehicle to enter sleep mode.
    • Identify faulty circuit by disconnecting fuses, relays, control modules or connectors, observing meter readings.
    • Defective circuit is found when current is below maximum closed current for vehicle being tested.
    use this link for more details http://www.e38.org/battery.pdf
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
    Join Date
    May 2010
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    Centerville, TN
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    My Cars
    1989 735i date 9/88

    My 735i shows manf date 9/88

    Per your question my car manf. date = 9/88. Is it likely a relay may be sticking points causing this drain? I will now consult wiring diagrams you so kindly supplied. Much thanks! FWIW, removing fuse 17 had no effect on amp draw.
    Last edited by shogun; 03-17-2024 at 06:12 PM. Reason: unnecessary quote removed, use reply button instead of reply with quote

  4. #4
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    1989 735i date 9/88
    Unfortunate that the wiring info shows fuse details which skip over any info about fuse 23. Details about the DME unit would have been helpful as well.

  5. #5
    Join Date
    Jan 2005
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    11/88 E32 750iL+98 E36M3
    add the 09/88 to your profile: My Cars 1989 735 , then you always have it shown automatically and no need to post such info in new threads. DME 1.3 details are shown in the ETM section from page 1360-00 to 1360 - 09 https://shark.armchair.mb.ca/~dave/BMW/e32/e32_89.pdf DME details are shown electr. section in the Bentley repair manual. The ETM has ~ 500 pages, it contains a lot of info when you take the time to read it all. Usually a sticking relay can be felt when you touch it, could be warm/hot.
    Last edited by shogun; 03-17-2024 at 07:30 PM.
    Shogun tricks and tips for the E32 series are HERE!

  6. #6
    Join Date
    May 2010
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    Centerville, TN
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    1989 735i date 9/88
    Thank you for your kind response. You have helped me before and I do appreciate it. The links provided are just what I need. It appears fuse 23 gets fed from the main relay then fuel pump relay, then sends current to the fuel pump wiring. I will check the relays for warm feel and then open up the fuel pump access panel to check wiring there. I have replaced the fuel pump and it is possible I pinched a wire I suppose. Thanks again!
    Last edited by rustfarmer; 03-17-2024 at 07:13 PM.

  7. #7
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    May 2010
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    1989 735i date 9/88
    I found that if I tap on the wiring connector to the DME, amperage draw drops from 260 ma to 159 ma, so I took the connector apart and sprayed electrical contact cleaner into both halves, dried completely, wiped a thin layer of dielectric grease onto the female part and reinstalled the part. The draw now stays steady at 159 ma but I am not totally sure the unit is going into sleep mode. Next I will close the hood and all doors with one window open just enough to pull meter leads out and let it sit for half an hour while testing to see if anything changes. Thanks again.

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