Haunted spedometer

[remta1]

when I got my car the speedo wasn't connected now I have reconnected it and just goes haywire .... backwards and forwards like a geiga counter 

[fy469rtse]

Try and keep constant pressure with your foot, speedo's just matching the way you drive lol, 

[Ghoste]

Does it make any noise?  You could try lubing the cable with some dry graphite but it could just be that the magnets in the head need to be "recharged".

[XH29N0G]

I think there are different causes of this.  My understanding is that the speedometer moves the needle by creating a magnetic field with something that spins.  If anything binds (in the speedo cable or the speedometer head itself) it will jump all over the place.  For some, I hear it is simply a matter of changing the cable.  I did that and had no real change, then I took mine out of the dash and spun it without the cable and had the same think happen when I spun the speedo with a drill.  (This may not have been advised, but I tested it that way).  I tried to clean up the mechanism in the speedo head with solvent, and am still waiting to test it out.  At least it worked smoothly with the drill after doing that.

It may be that you need a replacement speedo or cable, both of which are available.

Others will know more about this than I, so pay attention to them if they contradict/correct what I have written.

[John_Kunkel]

Testing the speedo head with a drill is perfectly acceptable, I do it all the time. FYI, 1000 rpm is 60 mph.

[myk]

My speedo acted the same way when I first got my car, but it settled over the years even though I discovered that the cable is bent at the tip.  I have a new cable/housing but I'll install it when I get a round-tuit.  'OP I would try lubing before replacing...

[A383Wing]

sounds like the brass bushing-bearing inside the speedo head is bad

[XH29N0G]

Testing the speedo head with a drill is perfectly acceptable, I do it all the time. FYI, 1000 rpm is 60 mph.

So  my drill only does 1000 RPM.  Also does 0-1000 RPM super quick.

[remta1]

sounds like the brass bushing-bearing inside the speedo head is bad

can I fix the bearing without pulling the speedo out or the housing out of the dash ?

[XH29N0G]

My guess is that you will have to pull the speedo out of the dash and the cluster.  I just went through this myself, and found the section(s) on cluster restoration valuable for guiding me through the process.  Although I know it must be possible to fix these things ourselves (e.g., replacing the bushing bearing or whatever is wrong with mine or yours), I was not able to figure it out.  Ended up immersing the speedo head in isopropyl alchohol and spinning it, in an effort to clean up anything that was binding.  There has been some improvement, but I have yet to see if it is really working properly above 60 mph.  Won't know until it warms back up outside.

If you figure out how to repair the head or find a resource for this, I would very much appreciate seeing the information posted.

[fy469rtse]

Ok seriously , had one do that, try lubricating the cable first, sometimes that's all it takes, next I would look at your plastic speedo gear in trans,I had another one do that because of the gear worn and teeth missing, take it out and see if teeth worn missing, do the easy stuff and eliminate those first, some of those plastic gears over forty years old , do like Myk said check the very ends of cable are straight,

[XH29N0G]

Ok seriously , had one do that, try lubricating the cable first, sometimes that's all it takes, next I would look at your plastic speedo gear in trans,I had another one do that because of the gear worn and teeth missing, take it out and see if teeth worn missing, do the easy stuff and eliminate those first, some of those plastic gears over forty years old , do like Myk said check the very ends of cable are straight,

Apologies - yes absolutely check the cable and speedo pinion gear in the transmission first.

[A383Wing]

sounds like the brass bushing-bearing inside the speedo head is bad

can I fix the bearing without pulling the speedo out or the housing out of the dash ?

no, speedo has to be removed from dash and taken apart by someone who knows what they are doing and with correct tools

[XH29N0G]

So I did my test today since it was warm.  I had a similar bouncing needle, but new cable.  Previously I had taken out the speedometer and dunked it in isopropyl alcohol to degrease, and then spun it with a drill, and repeated a number of times.  I had a chance to take the car out and run the speedo up into the 80's (wrong pinion gear so I was not speeding) and there was not bouncing.  At least for now, it seems that whatever was causing the oscillation (binding) is washed out.  I will see how long it lasts.

[remta1]

just ordered a new cable , fingers crossed....