1985 535i speedo & cruise inop

[memovox]

I have a beautiful low mileage original 535i that has an inoperative speedometer and cruise control. BOTH never work. I checked online in some sites including this one and all said a.) clean the connector on the vehicle speed sensor to fix the problem and b.) replace the vehicle speed sensor loocated on the differential. . . I did both and have no luck AT ALL. No dash lights for the cruise ever come on ever when moving the lever in any of its four positions. The speedo has never worked. I also noticed on occasion the temerature gauge is erratic on the dash. A light tap on the dash and it jumps into its position according to engine temperature. All else on the car is fine. I checked the fuse box too and all is fine. Do I have a bad relay or something? If so where is it located? I am very mechanically inclined so please dont be afraid to provide details. . .I would appreciate any and all feddback. Thanks - Chris, Elgin, Illinois.

[4-Door Flunky]

Hi, Memo-
On your overhead display, do you have "Brake Lights" lit up?
I'm currently having the same problem. My speedometer quit working. As soon as the speedo quits, the computer doesn't have that information, and it can't run the cruise control either, so they both quit. When you fix the speedo, your cruise will work fine.
My problem started at the exact same time that the brake light warning lamp on the overhead display started giving me a readout...which is why I was curious if you had the same problem.
Most of the information you'll need to fix a speedo can be found at the unofficialbmw site. It's here:
http://www.unofficialbmw.com/frame_e28.html

Look at Interior, and click on "Fixing a defective speedometer Courtesy of Jeff Schnellinger"

I did everything they mentioned, and my speedo doesn't work yet. I think that's because I've got a short. I've taken out the back seat, played with the wires there, under the car, cleaned the connection going into the differential, you name it, and mine still won't work. Although about once a week I hit a bump and it works for a bit, so I know it is hooked up.
Getting the instrument cluster out of the dash is surprisingly easy. There are only two screws that hold it in. Just remember to telescope your steering wheel all the way out to make a little more room. Once you've got it out, you can play with the wires back there. One of them is your temperature guage wire. You should be able to snap it back on good and fix that problem forever.
Good luck.
Flunky
PS-Did you take out the sensor on the differential? That's my next step. Tell me how and what you did back there, please.

[memovox]

How funny - Yes, the over head brake light comes on ONLY when I start the car and turns off when I tap the brake pedal , you know like backing out of the driveway for the first time and hitting the brakes. . . Could this be the brake switch is bad or that the computer has issue like you eluded to and doesnt store the info or something? What is the status of yours now? Maybe you can email me directly at memovox@aol.com. I would like to solve this sans dealer support. . . I am very mechanically inclined and can do the repair whatever it is my self. And, yes, I put in a brand new $44.00 speed sensor on the rear diff and cleaned the terminals even though they looked like new. . . please assist! - Chris Walsh.

[webhak]

Chris,

The brake light indicator light is functioning as intended. Mine does the same thing. Flunky and I, however, have a break light indicator that pops on when driving. We both noticed that our speedos went kablooey shortly after that started happening. Mine is somehow tied to the radio being inoperable as well. When the speedo works, the radio works. When the speedo doesn't work, the radio doesn't work.

I haven't had a chance to get in there and look around yet since my main project right now is to resolve the car running hot by replacing the fan clutch this weekend.

The next project after that will be to replace the front rotors and brake pads.

Then, I'll hopefully get to the speedo.

[memovox]

Thanks for the reply ------ Heres the latest. . . I took out the inst. cluster and speedo head. I carefully examined it and resoldered/reflowed the solder joints. Then reassembled the whole thing as it wasnt that hard but still have no luck. At least I got to dust off the light bulbs in there. . . Seriously, the only thing that I still am not for sure on is there are a three plugs that plug in on the back side of the speedo that I am not sure which way they go back in. The one must be the cruise lead and another the temperature lead and the third the speed sensor lead? ? ? Two of those smaller plugs are blue and one is white or clear. The back of the speed is not color coded......please advise!!!!!!!!!!! So again ,I have a new speed sensor, reflowed solder on the VDO speedo head, and no cruise, no speedometer, and an erratic occasionaly working temperature gauge................

[4-Door Flunky]

Hi, Memo-
Before my speedo troubles started, my overhead brake light indicator would do the same thing: come on at first start up, and then go off the first time I touched the brakes.
A couple of weeks later it stayed on all the time, and that's when my speedo started screwing up.
I took out the speedo and reflowed all the joints, just like the web site at unofficialBMW that I recommended to Web.
I played with the connector going into the differential, namely, I unplugged it, cleaned things up (by the way, some water trickled out of the plug (not the sensor) when I took it off), and stuck it back on there.
No change. Still no speedo, upper brake light indicator still on constantly.
So, I got all pissed off and decided I had a short in the system. I looked for places where the wires might be worn through, grounding out on the body. I checked the place where the bundle of wires goes from the differential through the body, coming out under the back seat.
I took out the back seat (boy, did I find some ugly crap down there...if you haven't taken your back seat out, do so. Jimmy Hoffa could be under there...along with 10 year old melted ice cream bars, sunflower seeds, and a small vial of some powder (Sniff!) I have yet to identify...)
Anyway, the wires were fine. I vacuumed under there and put the seat back.
Replacing the sensor was going to be my next step, until I found out you did the same thing.
I'm basically lost now.
Hey-Could you send me your old sensor? It's probably still good...
Flunky

[4-Door Flunky]

PS-When I took out my speedo, I also had two blue plugs. One of them isn't supposed to be hooked up. You are indeed supposed to have one blue one left over that isn't connected to anything.
The first time I put my speedo back together, my temp guage worked for an hour, and then quit. I took the speedo out again and clipped those wires back on a little better, and it's been working fine since then.
Hope you got it figured out!
Flunky

[4-Door Flunky]

While your speedo isn't working here are a few tach tips:
3,000 rpm in 5th gear is very close to 85 mph. That's useful on the interstate here in NM.
2,000 rpm in 5th gear is around 62 mph, perfect for 55mph cruising.
2,500 rpm in 5th gear is very close to 70 mph. Good for those 65 MPH speed limit zones.
Flunky
PS-I'm running 205 60r14 tires.

[BigDaddy2U]

Had same problem on 1985 535i ---Check fuses for loose contact or corosion.