Speedometer won’t go back to 0?????

Bought a used speedometer for my 72 d100 and it was at zero when I pulled it from dash, got it home and installed and it was at 10mph, then installed it in the car and now it’s at 20/22 and won’t go back down? Thoughts, suggestions?

Thanks,
Jake-non member, member

The pickup input is magnetic, not mechanical.

Did the magnet pick up any debris that would stick to it?

I pulled one out of a running car years ago, the car had the normal leaks at the wiper transmission pivots due to aged seals.

The speedometer magnet had picked up enough magnetic 'rust dust' to cause what you just described.

Alaskan_TA said:

The pickup input is magnetic, not mechanical.

Did the magnet pick up any debris that would stick to it?

I pulled one out of a running car years ago, the car had the normal leaks at the wiper transmission pivots due to aged seals.

The speedometer magnet had picked up enough magnetic 'rust dust' to cause what you just described.

Click to expand...

I didn’t realize that. I’ll have to pull it back apart and do some more investigating. Thanks for the heads up, much appreciated.

Jake-remembered member

Worth a look.

In my case, there was enough metallic 'fuzz' between the magnet & the pick up sensor for the magnet to cling to & prevent movement.

I wish now that I had taken before & after photos!

Jake I know in our 67 cuda there is a small brass "spacer" that slips on cable end before before being threaded onto speedometer. We omitted it by mistake and needle would bounce. Not sure if setup is same as yours.

On my 80,the overlay had a bubble so to speak. Needle was a little warped too,and it dragged on the overlay.
I tried to pull the needle up on the shaft and broke it.
I found a vacuum tee or a washer fluid tee and it fit the speedo shaft. A red noodle from a spray can for the needle. Wouldnt know it when you look at it.

If you need to pull the needle, modify a dinner fork...

xLURKxDOGx said:

Bought a used speedometer for my 72 d100 and it was at zero when I pulled it from dash, got it home and installed and it was at 10mph, then installed it in the car and now it’s at 20/22 and won’t go back down? Thoughts, suggestions?

Thanks,
Jake-non member, member

Click to expand...

I had a issue with my speedometer where it wouldn't go past 60, I got another speedo from a buddy and tested it and it worked. So I had to drop my steering wheel to get my steering box out that **** the bed on me so I decided to pull my instrument cluster to replace the speedo. Before I pulled the cluster apart I tested the speedo and it wouldn't go past 60. Pulled it apart got the speedo out tested it and it worked perfect. WTF, put it back together and it wouldn't go past 60. What I found was the front face plate when assembled was pushing against the long thin piece of tin that has the MPH numbers, temp, fuel, alt. and oil words on and it wasn't allowing the speedo needle to go past 60. So I took a couple of very thin nylon washers put them on top of the tin plate where the speedo is then assembled the face place. She now works perfect. Tested it and she spins right up to 120. That tin plate is very thin if you had it apart it's possible you might have bent it just enough to not allow the needle to go to zero. Just a thought.

the needle is on a hairspring to curl to zero and then hits a stop. There is no mechanical link between the needle and the magnetic spinner. I bet yours is dragging