Wonky speedo

[worzella]

Hello detectives... a case for you. Yes I have performed due diligence but wanted to describe my specific  clues

 

Rebuilt/cleaned my speedo a few years back and installed when got got running this past winter. Worked like a charm

 

A 75 with split cable through mile counter dummy light box. I cleaned and rebuilt the tranny side gear/seals and wired it in place

 

Lower cable new and lubed

 

Ripped guts out of counter box but still used it to connect lower/upper cables. Greased it well

 

Upper cable original ? and kicking myself for not replacing

 

Symptoms:

- After two months of working fine needle started flying all over dial

- I can stop car and needle might hang at 60, might hang at 10 or might hang at 0

- I temoved pads under dash and reached up to tighten top to speedo and it helped a bit, but still not correct or landing right when 0 mph

 

Sooooo... I am about to pull speedo but wondering how to debug?

 

I want to use a drill to drive speedo to see if it responds smoothly and I also thought of watching the upper cable as I drive to see if it is consistent

 

OK out of words???

 

Randy

[Simeon]

The hanging at speeds is an odd one but usually a wandering speed is a sign the cable is binding. The speed slows down as it binds and the cable winds up, it then comes free and whips around to where it should have been, flicking the needle on. 

 

Hanging up sounds like it might be internal to the speedo rather than the cable. 

[ray_]

The cable flange puts light pressure on the needle assembly, allowing it to "float" above (away from) the gauge itself.  Your needle is likely contacting the speedo face.

 

Mine's doing it too. I haven't researched the fix yet. 

 

Cheers,

[PaulTWinterton]

I think it's the guts of the speedo that need attention.  Disregard the odometer part of the following post.  Get out the crazy glue.

 

https://www.bmw2002faq.com/forums/topic/183212-more-on-speedoodometer-repair/

 

 

Edited July 10, 2018 by PaulTWinterton

[TVeye]

Just give NoHo speedo $250 :)

[Buckeye]

Grab some popcorn and watch the video. Post and link by FunkyLaneO on 2nd page.

 

[worzella]

Thanks all. I will begin the investigation and report back

 

One related question. As I learned in my recent dealings with charging system and alternator, the initial excitation current for the alt comes through the “L” bulb wiring. 

 

So if I pull my instrument cluster but run the car, am I correct in assuming my battery will not be charging

 

More curious than anything. I do not plan to drive it far or long without the cluster

 

Randy

[jimk]

1 hour ago, worzella said:

the initial excitation current for the alt comes through the “L” bulb wiring. 

No, that would be a dumb design.  If the bulb were to burn out the charging system would come down.  Bulbs light up when current flows thru them.  Current flows thru the bulb when one side of the bulb has a greater voltage then the other side.  The bulb lights when the battery voltage is greater than the alternator output voltage and serves no control function.

[Stevenc22]

Just replace the the two piece cable with a early model 1 piece cable from the tranny to the speedo. Eliminate more variables that way!

 

$36

 

https://www.partsgeek.com/gbproducts/WC/13607-01075648.html?utm_content=YN&utm_term=1968-1976+BMW+2002+Speedometer+Cable+Gemo+W0133-1624575+68-76+BMW+Speedometer+Cable+1975+1970&fp=pp&gbm=a&utm_source=google&utm_medium=ff&utm_campaign=PartsGeek+Google+Base&gclid=CjwKCAjwspHaBRBFEiwA0eM3kfHE5h3eEJM537dhv_H8abnWFVWomYCr80TlDK24eINhONhcY5UkNRoC6ZUQAvD_BwE&ad=47433964212

[Mike Self]

From your description, Buckeye's analysis is probably the correct one.  I speak from experience as the same thing happened to my '73 twice, but never on my '69.  And Jim Denker's 73 is doing the same thing.  

 

It's a fiddly, but relatively easy fix.  Takes longer to R&R the speedo than it does to fix.

 

mike

[wegweiser]

On my 2016 drive from Pittsburgh PA to Monterey CA (then San Fran, then home) the only mechanical failure was the speedo going psycho somewhere in Indiana, on the way home. 

 

Having dealt with several well known gauge repair shops across the country throughout the years, I can say that I've had the best experience with Buz Ras at Seattle Speedometer. He restores and repairs some VERY unique and rare gauges and is a diehard enthusiast.

 

As for the bad experiences with some of the "big names" in gauge repair - all I can say is: NOTHING will ruin your week, like spending 7 hours re-installing an old Benz speedo - only to find out it wasn't repaired properly. I had to walk outside until the rage subsided.  

 

On the one occasion, where Seattle Speedo didn't get things right (on a Porsche gauge) he was willing to stand behind his work and immediately, without extra cost or hesitation, double check and correct the problem. I think the manner in which a company deals with their mistakes is testament to their character and customer service commitment. I'll never go anywhere else for gauge repair. Just my two cents worth as a professional. NH, Bob's, and others have repeatedly let me down…. maybe I'm just unlucky. 

[Guy Cocquyt]

I am not so sure about that. A former owner cut the blue wire from the alternator to the dash lamp (no idea why). I was getting no ignition light when starting and no charge. Repaired blue wire, light came on at ignition and then went out and I was getting charge. Anyway you can run your car off the battery for a surprising distance (experience speaking here).

Sent from my STH100-1 using Tapatalk

[deanres]

I had good luck with: http://www.speedometer.com/ they are in Austin TX and it took about a week as I remember. Just pack carefully and ship it. And I had the issue where the needle hung at all sorts of speed. 

[02Les]

28 minutes ago, deanres said:

I had good luck with: http://www.speedometer.com/ they are in Austin TX and it took about a week as I remember. Just pack carefully and ship it. And I had the issue where the needle hung at all sorts of speed. 

+1 for Rick Borth. I understand he has a proper workshop now, but, many years ago when he repaired my Touring's speedo (it's still going strong) he worked in a room in his house.

Can't imagine any Austin '02ers needing to go anywhere else.

[Vicleonardo1]

10 hours ago, Guy Cocquyt said:

I am not so sure about that. A former owner cut the blue wire from the alternator to the dash lamp (no idea why). I was getting no ignition light when starting and no charge. Repaired blue wire, light came on at ignition and then went out and I was getting charge. Anyway you can run your car off the battery for a surprising distance (experience speaking here).

Sent from my STH100-1 using Tapatalk
 

Was he just following instructions? This is much like me working on auto electrical. (Pre Hack Mechanic guide) ?