General service questions- '85 735i

Just recently purchased an 85 735i. My first BMW. As beautiful as the condition is, it still needs a tiny bit of TLC. I'm finding that tracking down info on this car is a challenge, so I'm glad I came across this forum. Hopefully, someone, or someones can give me a little insight into a few of the issues I have.
Oh yeah, I'm a total do-it-yourselfer, so technical difficulty is no issue.

Oil and inspection lights..how do I reset those? I saw with regard to a 318 that it's accomplished by shorting out pins 7 and 19 on the test connector. Is it a similar procedure on this 735?

I have an issue with the oil pressure light *sometimes* flickering on at idle. If it happens at all, it's after the car is nice and hot. It goes out when I come off idle. But it doesn't ALWAYS behave this way. Sometimes I drive it all day, no light. Other times, a spin around the block and it comes on. This leads me to think it's an electrical issue, and not an oil pressure problem. Any common problems with the oil pressure lights I can look into?

Darned if I understand the heater controls in this car. I even resorted to RTFM (reading the friggin manual) and it sure didn't help me one whit. I'm assuming the motor speed control is hosed. I've seen various articles on addressing the various control systems for the motors, but nothing very concise. Any advise on component location, and suspect items is greatly appreciated. Even a little narrative on how the system is SUPPOSED to work would be a good start.

Electrical diagrams and schematics. These seem to be a real commodity. Haven't found a single source for these yet. Anyone who has or knows where I can get an abbreviated set (Chiltons or Haynes type) would be a great start.

Lastly, any info on an interface that can be built to extract and monitor codes, measurements, readings, and conditions with a laptop (or other computer) that might be available. I built one for my Fiero (before yanking all the F/I stuff and setting a Holley 390 on there....) (but that's a different topic altogether) so I figure some electronics guru probably has something similar designed for the BMW.

Anyway, that's about it (gee, that's ALL?) thanks in advance for any help, advice, comments, or other words of wisdom are greatly appreciated.

Ciao
~Taiji

You seem to have many questions. I have extensive information on this model and specifically on your concerns. Feel free to e-mail me at [email protected] and I will be happy to give you as much information on your concerns as possible. I think my response here would be way too long.

Regarding your "new" '85 735:

Service indicator - try replacing the NiCad battery located on back of Instrument cluster, they are usually dead by now - replacement from Radio Shack.

Oil pressure light - are you using 20/50 oil? If not, I recommend you use it, for best results, try Valvoline's Racing grade 20/50.

Heater/Air Conditioning push-button controls - far left switch is for recycling interior air - best used on hot days - Bi-level switches (both Heat and Air Cond.) ducts air thru floor and defroster vents using fresh air, the other remaining two switches (both Heat and Air Cond.) ducts air thru main dash vents using fresh air - finally, the far right switch over rides sytem to duct maximum heat thru defroster vents.

Drum switches - left is fan variable speed, right is temperature which you set and forget - it's like Lincoln's "All-Climate" system only German.

With age, these switches are famous for not working properly, BMW parts houses like BMP have rebuilt and new ones, $$$. You have to remove the radio to access switches. As with all "aged" electrical items, their contacts get dirty - try using electronic contact cleaner (Radio Shack) before replacing. Servicing these is pain in the a-- work but eventually worth it.

Haynes still publishes a general manual that covers this model along with other mid '80s BMW models - try a good local auto parts store, or BMP, or Amazon.com.

It's your car, but I wouldn't screw with the BMW electronics - plug in a new computer chip if what you want is more power. And use injector cleaner periodically - two containers per (23 gallons!) tank.

H & R Springs and 16" wheels/tires will add to it's appearance and handling - making the 85 735 a fun car, enjoy!

- Long time BMW owner -

I've got a 733i that i bought three weeks ago and I have many of the same problems, or chalanges whatever, let me know what your doing with the electronics, and how or if you can link to the onboard computer to get a self diagnostic, that would save me loads of time i'm resorting to testing each switch and wire, a beter quicker method will be well apreciated, please keep me updated, I,m looking for a contact or a source to get replacment parts also I have wireing diagrams for my model but their are incomplete, so I have to find a complet set, if i come across a 735 i could e-mail them to you. let me know