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Thread: Just bought my first BMW, a 1985 735i... could use some tips

  1. #1
    Join Date
    Apr 2018
    Location
    Los Angeles
    Posts
    6
    My Cars
    85 BMW 735i

    Just bought my first BMW, a 1985 735i... could use some tips

    Hello everyone, i just bought my first BMW! A 1985 735i, in great cosmetic shape! Although i have worked on many over the years shes my first, I bought this car from a customer at my auto repair shop for a few hundred dollars. First, it would not start, the relay on the passenger engine bay firewall had failed, and also the little metal pickup tab on the flexplate had fallen off, (the one that magnetic triggers the crank sensor)so i made a new one and welded it in place. Then, It wouldn't come out of first gear, so i found the shift cable had broken inside the trans, so now i've replaced it with oem bmw, and it runs and shifts great through all gears. I also replaced all the coolant hoses and all 3 belts, all power steer/brake hydraulic lines new, and all fresh fluids and filters. Spark plugs, wires, cap, rotor, and valve cover gasket and i adjusted the valves. Needless to say the car runs spectacular. Its in great shape but needs a little tlc. the engine and trans are working perfectly, but im having a few issues. any help of suggestions would greatly help me (I am quite good at diagnostics and wiring) Just looking for some guys with experience to send me in the right direction. Here's my issues:

    First issue:
    The dreaded HVAC: the blower wouldn't come on no matter what; i pulled out the motor and bench tested it (worked great) put it back in and traced a green wire (i think) by the glovebox, it had a glass fuse inside making poor connection, cleaned it up and all fan speeds worked. Obviously it didnt blow cold as it needs freon and probably a compressor which i will replace as soon as i get the hvac reliable) Then suddenly a couple days later the fan stopped completely. Here's what i noticed; the fan wheel (on the control) activates a relay i hear in dash and clicks but no blower, when i select the different vent positions (behr push button unit) i hear clicks, but sometimes the green lights under dont come on, or i must push it again and it will flicker and come on, I tried cleaning the contacts with same result, now, i have a question! my vac pump is bad, does this only effect vent selection and positions? or would this render the blower inoperable? Also, i hear some people say this car may have two blowers? I found one under the cowl. I'm thinking of using a ford vacuum pump i have at the shop, i think this will be ok for this? It is a small 12v off a 1999 ford super duty.

    Second issue:
    My speedometer works only when she feels like it, and the odometer doesn't ever work. Would this be some sort of bad circuit board connection in the cluster? And does the odometer work off a gear? I've seen these gears deteriorate to dust in a few chevys before...

    Overall, I'm pretty happy with this car and is in good shape, i would really like to get everything fixed and in proper working order, so i can decide if i will keep it, or sell it. It's a beautiful car and i love the black exterior and burgundy/ dark grey interior. I'd just like to have these last few issues sorted out so i can go onto the loose front wheel bearings and rear suspension clunk, and get the ac leak fixed and charged up...

    Any help or tips greatly appreciated, sorry for the long post, i jut wanted to be thorough.

  2. #2
    Join Date
    Mar 2007
    Location
    Quadratechtown, PA
    Posts
    741
    My Cars
    5, 7, 4x4
    odometergears.com Electrical from diff to board then gears for the odo. Maybe the Service Interval Indicator batteries will cause some gauge issues but I don't know which to blame. Rechargeables that die and leak.

    vacuum pump is only for help to manifold vacuum supplying the HVAC. The fitting is on the bottom of the intake manifold and has a hose that runs to the HVAC vacuum lines near the pump. Pumps always die, they are on constantly when the vacuum of the system leaks (broken T-fitting to the egg crate reservoir under the pass side cowl or a leaking dashpot.

    Talk to us about what you do to repair the vacuum system. Some have bad motors.

    The HVAC defaults to defrost with the lack of vacuum, can't move the dashpots so default is the safety of a clear windshield.

    You have the BMW repair manual? the Bentley for the 82-88 5-Series (similar drivetrain) and the ETM, electrical manual and know about the on-line ETK, parts diagrams? What about an owners manual?
    Last edited by 8991XJ; 04-13-2018 at 02:13 PM.

  3. #3
    Join Date
    Mar 2006
    Location
    Sacramento, CA
    Posts
    935
    My Cars
    87 535i/84 €735i/8
    Welcome!
    You've already fixed 2 things that would have defeated most new owners, well done sir.
    I'm just waiting for Hitman to chime in wtih "The goddam HVAC isn't that complicated! its just pods!"
    Vacuum pods can go bad, but most of the issues are with sensors/electrical TELLING those vacuum pods to open/close.
    There are lots of tech docs available on how to troubleshoot the auto HVAC system, lucky for you.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  4. #4
    Join Date
    Jun 2010
    Location
    TX
    Posts
    4,487
    My Cars
    1983/84/85 745i

    Thumbs up



    But it is true. Most of the horror stuff online is armchair mechanics. Resolder the two boards, replace the microswitch. Done. Pretty much assured to work trouble free for a decade.

    The wing cell compressor is not terrible, but it is with 134A. Pull a vac on it and shoot in three, 10oz cans of air duster. Now it will blow about as cold as an R12 car while you sort the vacuum issues provided the compressor has not seized. If it has, no big deal.

    Do not get me started on that plastic 'T' fitting on the vacuum reservoir under the cowl...FYI you can delete one cowl flap and the system works fine, they both close on max AC anyway.



    Anyway, welcome to the site. Post pics!
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  5. #5
    Join Date
    Apr 2018
    Location
    Los Angeles
    Posts
    6
    My Cars
    85 BMW 735i
    OK thank you, I vacuum tested the cowl vents and repared a few broken vacuum bits and such while I. Had the cowl off. When I tested the cowl vaccum they both actuated and held no problems. I did notice one vacuum actuator behind the climate control unit (directly behind to the right) was broken and wire tied open. I will find a rebuild kit for this one.. But as far as replacing the microswitch,. Could this be causing me no blower at any speed? I hear a relay click when I turn the fan thumbwheel switch on...

    And unfortunately I do not have the owners manual 😥 the car did have a Chilton repair manual... But yeah... Nothing in there new to me... I will look for the Bentley one...

    Let me post some pictures of the car...

  6. #6
    Join Date
    Apr 2018
    Location
    Los Angeles
    Posts
    6
    My Cars
    85 BMW 735i


    - - - Updated - - -




  7. #7
    Join Date
    Mar 2006
    Location
    Sacramento, CA
    Posts
    935
    My Cars
    87 535i/84 €735i/8
    Photobucket no bueno...
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  8. #8
    Join Date
    May 2012
    Location
    Boynton Beach, Florida
    Posts
    1,526
    My Cars
    1990 735I (E32) M30
    If you get a little crazy trying to fix the wheels or the set of buttons for the HVAC, there's an easy and inexpensive swap. Programa will either fix yours or just take yours and send you one already fixed off the shelf. Prices have come way down. When I had my E23, I bought the Cluster and the Cluster Battery Board. Was an easy swap. Just had to remember to give that steering wheel a 1/4 of a turn to the left to be able to remove the cluster itself. Recently I bought the SWORD for my E32 and all is well. Just in case you find these two pieces are not fixable. Some people don't like Programa, but I love these people. Also they're ten minutes from my house. They've turned over a few times and the Techs working there now are really good.
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=2d4tHoHGaJo
    https://1drv.ms/v/s!Av20xCMMocSsyEpl...h_oOk?e=ekIcAT







  9. #9
    Join Date
    Nov 2012
    Location
    Los Angeles, Ca.
    Posts
    14
    My Cars
    e23,e24,e28,e31,e39
    I have the same problem with intermittent on and off of the HEVAC system and the turning of the thumb wheel fan control. Sometimes the system will work and sometimes nothing happens when i try and turn on air flow. Please post whatever repair you were able to find and or make to the system to get it all operational.

    Thanks.

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