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Thread: '89 735i battery drain

  1. #1
    Join Date
    Nov 2018
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    Oklahoma
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    My Cars
    1989 BMW 735i

    '89 735i battery drain

    I know that there are many threads already started on this topic and while I probably could have posted it there, I wanted a fresh start to post my symptoms and what I've already checked.

    I have an '89 735i that has a parasitic drain of 300-500 milliamps. If I start the car everyday, it's fine but it's not my daily driver so it sits for a couple of days at a time and is dead by the next time I try to drive it. When you first check it, its at 500 mA. After about 5-6 seconds, it drops to 300mA (not sure what this could be). Alternator and battery both check out. I have found that the drain is across fuse 20 in the engine fuse box which is described as Instrument cluster, heating. I have also seen on here that it controls central locking and some other things. I have removed the power to all 4 doors, ccm, gm, and rm and have yet to find the drain. This little gremlin has been taunting me for the past 5-6 months while I went to school full time and tried to figure it out over the weekends. I am ready to get it figured out so I can drive it again and any help would be much appreciated.

    Note:
    Central locking currently doesn't work on my car and the blender doors do not currently work. they work when in a/c but switch over to heat and it only comes out the defrost vents and foot vents, nothing comes out the main vents. I recently replaced the turn signal stalk (old one broke) and my instrument cluster has a new board from ProgRama but still is finicky. The light behind the fuel gauge doesn't come on even though the light is brand new. In the winter when it is cold the instrument cluster takes some time before it will work.

  2. #2
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    1989 ETM is here http://shark.armchair.mb.ca/~dave/BMW/e32/e32_89.pdf
    fuse 20 on a 735 covers:
    antitheft system DWA, also fuse 17,18,31
    automatic climate control IHKA , also fuse 9,19,21 29
    There you have the IHKA control module behind the center console, that has 4 plugs, you can for example disconnect one after the other and see if that changes the mA, pinout is here for IHKA module and sword http://www.bimmerboard.com/forums/posts/426626/
    brake lining warning, also fuse 1, 17
    EML (electronic throttle valve, in vase your has has it)
    instrument cluster/check control, also fuses 1,12,15,17,29,33 (These you could for example disconnect for a test)
    OBC, also fuses 15,17
    park ventilation
    park,tail, underhood lights, also fuses 1,4,5
    power windows ZKE, also 17,30,31,44
    sunroof ZKE, also 17,30,31, 44

    I would start with the IHKA and sword. Disconnect each plug one by one and measure.

    How to test here under electronics, http://www.e38.org/e32/ direct links below

    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 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

    Blender doors, info http://bmwe32.masscom.net/johan/ihka/ihka.html
    maybe the brackets are broken
    http://www.bimmerboard.com/forums/posts/200205/
    http://www.bimmerboard.com/forums/posts/1106458/
    Last edited by shogun; 06-15-2019 at 09:15 AM.
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
    Join Date
    Jan 2005
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    Japan
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    54,654
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    11/88 E32 750iL+98 E36M3
    Any progress with solving your problems?
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
    Join Date
    Jan 2010
    Location
    Brantford ON Canada
    Posts
    1,630
    My Cars
    735iL - 1989
    Quote Originally Posted by Storeytime64 View Post
    I know that there are many threads already started on this topic and while I probably could have posted it there, I wanted a fresh start to post my symptoms and what I've already checked.

    I have an '89 735i that has a parasitic drain of 300-500 milliamps. If I start the car everyday, it's fine but it's not my daily driver so it sits for a couple of days at a time and is dead by the next time I try to drive it. When you first check it, its at 500 mA. After about 5-6 seconds, it drops to 300mA (not sure what this could be). Alternator and battery both check out. I have found that the drain is across fuse 20 in the engine fuse box which is described as Instrument cluster, heating. I have also seen on here that it controls central locking and some other things. I have removed the power to all 4 doors, ccm, gm, and rm and have yet to find the drain. This little gremlin has been taunting me for the past 5-6 months while I went to school full time and tried to figure it out over the weekends. I am ready to get it figured out so I can drive it again and any help would be much appreciated.

    Note:
    Central locking currently doesn't work on my car and the blender doors do not currently work. they work when in a/c but switch over to heat and it only comes out the defrost vents and foot vents, nothing comes out the main vents. I recently replaced the turn signal stalk (old one broke) and my instrument cluster has a new board from ProgRama but still is finicky. The light behind the fuel gauge doesn't come on even though the light is brand new. In the winter when it is cold the instrument cluster takes some time before it will work.
    Looking at page 0671-06, you can see all the loads that are fed by F20.

    You can open, in sequence:

    remove the CCM,
    X13 (7100-08-03),
    X34 (7100-23-01),
    X36 (7100-23-01)
    to isolate those loads.

    That leaves only the A2 Instrument Cluster as the last suspect.

  5. #5
    Join Date
    Jan 2005
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    Japan
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    11/88 E32 750iL+98 E36M3
    and another story and how it was fixed, German version and thereafter the google translation

    Fehlersuche Ruhestrom - Leidiges Thema: Batterie ist nach 1-2 Tagen Standzeit leer. Ich habe an der Batterie den Strom gemessen:
    Zündung aus, Türen offen: 1,4 A (LED Beleuchtung für den Innenraum)
    Zündung aus, Türen zu, 1 Minute gewartet: 0,6A
    0,6A = 600mA sind als Ruhestrom zu viel! Es lässt sich leicht ausrechnen wann die Batterie so weit geschwächt ist, dass der Anlasser nicht mehr genug Leistung bekommt.

    Fehlersuche:
    Ampermeter so anschliessen, dass der Strom von außen bei geschlossenen Türen abgelesen werden kann.
    Im Motorraum nun eine Sicherung nach der anderen ziehen
    Strom kontrollieren
    Stromverbrauch gesunken?
    Nein: Sicherung wieder rein und zurück zu Punkt 2
    Ja: Stromkreis gefunden

    Hinweis: Wenn ihr im Verteilerkasten im Motorraum durch seid ohne Erfolg, dann sind unter der Rücksitzbank noch mehr Sicherungen.

    Was soll ich sagen: Bei mir war es Sicherung 20 (Für die Insider: Oh welch ein Wunder).
    Was hängt an Sicherung 20: Alte Bekannte...
    IHKA
    Standheizung
    ...

    "Natürlich" habe ich gleich das IHKA in Verdacht gehabt. Ich habe das also ausgebaut. Danach habe ich das IHKA repariert:
    Transistor 520 getauscht
    Leistungstransistor getauscht

    Warum habe ich den Leistungstransistor getauscht? Ich habe messen können, dass auf der Basis ein zu geringer Wiederstand zum Collector hin war. Meine Vermutung ist, dass dadurch auf Transistor 520 ein zu hoher Strom fliest und dieser dann kaputt geht. Die eigentliche Ursache dürfte aber der Leistungstransistor sein.

    Nun IHKA wieder eingebaut und auf Funktion getestet. Perfekt. ABER: Der Ruhestrom ist nur auf 0,3A =300mA gesunken! Das ist noch immer zu viel! Wieder Sicherung 20 kontrolliert - noch immer zu viel Strom!

    Nun hat mein Wagen Standheizung + Standlüftung. Ein weiterer Fehler war nun in der Relaisbox für die Standlüftung 61311379737

    Nachdem ich auch dieses repariert habe, ist der Ruhestrom nun bei 0,02A-0,03A.

    Ich hatte also zwei Fehler:
    IHKA
    Relaisbox
    --------------
    Troubleshooting sleep mode current - topic: The battery is empty after 1-2 days when car is parked. I measured the current on the battery:
    Ignition off, doors open: 1.4 A (LED lighting for the interior)
    Ignition off, doors closed, waited 1 minute: 0.6A
    0.6A = 600mA is too much as sleep mode current! It is easy to calculate when the battery is so weak that the starter no longer gets enough power.

    Troubleshooting:
    Connect the ammeter so that the current can be read from the outside with the doors closed.
    Now pull one fuse after the other in the engine compartment
    Control current
    Has power consumption decreased?
    No: reinstall the fuse and go back to point 2
    Yes: circuit found

    Note: If you are unsuccessful in the fuse box in the engine compartment, then there are even more fuses under the back seat.

    What can I say: For me it was fuse 20 (For the insiders: "Oh what a miracle").
    What depends on fuse 20: Old friends ...
    IHKA
    Auxiliary heating
    ...

    "Of course," I immediately suspected the IHKA. So I removed that and repaired the IHKA:
    Transistor 520 replaced
    Power transistor replaced

    Why did I change the power transistor? I was able to measure that there was too little resistance to the collector on the basis. My guess is that this will cause too high a current to flow to transistor 520 and it will then break. The real cause is likely to be the power transistor.

    IHKA installed again and tested for function. Perfect. BUT: The sleep mode current has only dropped to 0.3A = 300mA! That is still too much! Fuse 20 checked again - still too much current!
    My car has auxiliary heating + auxiliary ventilation. Another error was now in the relay box for the auxiliary ventilation 61311379737. After repairing this too, the quiescent current is now 0.02A-0.03A.

    So I had two faults:
    IHKA
    Relay box auxiliary ventilation
    Shogun tricks and tips for the E32 series are HERE!

  6. #6
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
    Join Date
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    BFE
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    11,090
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    E34T
    Not exactly E32 or IHKA, by on my E34, I had a drain caused by a defective IHKR module leaving the temperature sampling fan on all the time. I ran a wire from disused Fuse 47 to X18156 pins 12 and 13. This makes the module entirely ignition-powered instead of drawing from the battery. The only loss of function was park ventilation, which I would never use anyway.
    Last edited by moroza; 11-01-2020 at 05:01 PM.

  7. #7
    Join Date
    May 2013
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    1990/02 BMW 735iA M30B35
    Does E32 750IL has interrupt battery switch for disconnect ground from chassis ? I would like to install one switch for cut off chassiss ground I think is good for winter season when temperature is below 0°C ?

  8. #8
    Join Date
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    11/88 E32 750iL+98 E36M3
    It does not have one, but you can install one. Ground cable is located in front of the rear seat passenger side under a plastic cap , pics from a 750iL with single electric rear seats
    http://www.ow.no/gallery2/main.php?g...b7c0e6cad89411
    http://www.ow.no/gallery2/main.php?g...b7c0e6cad89411
    http://www.ow.no/gallery2/main.php?g...b7c0e6cad89411
    or just lift the rear seat and disconnect the battery.
    Originally ex factory the cars came with a battery switch from Germany to the dealer in order to avoid battery drain on the long shipping voyage Germany to USA, then dealer removed that switch and it was returned to the BMW factory.

    The option is listed as
    S818A MAIN BATTERY SWITCH |Battery master switch 900A APPR. VEH.IMMOBILIZAT. ACC. TO AZT/TUEV Electronic immobilizer.

    89.jpg

    How to Attach a Car Battery Cut off Switch https://www.wikihow.com/Attach-a-Car...Cut-off-Switch
    Last edited by shogun; 12-10-2020 at 08:32 PM.
    Shogun tricks and tips for the E32 series are HERE!

  9. #9
    Join Date
    Nov 2005
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    Quebec Canada
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    92 735iL (12/1991)
    I would not install a kill switch for the ground on the car. Three years from now you would be chasing random drivability complaints caused by the wiring on this switch, or the switch failing.

    I would use the access panel that Shogun mentioned. Just remove the wire and reconnect it securely when you're done.

    90,700 miles 1992 BMW 735iL Azure Blue Metallic with Silver Grey leather interior ‣My car ‣My YouTube channel

  10. #10
    Join Date
    May 2013
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    1990/02 BMW 735iA M30B35
    The think only when power will cut off by manual switch from inside a car the central locking won't work it have to close manually from inside 3 doors and one door should be locked from outside or ether way to get remote cut off switch is also good.

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