By disconnecting and inspecting itNo, I have not, how do I do that?
My sad news is....
Your going to have to pull the cluster.
Pull out the front seats.
Pull out the steering column.
Tape up the dash.
And be ready to get your hands cut up
And go easy on the wires and connectors.
Be prepared to replace or repair the cir boards.
After the cluster is out find a reputable repair shop in your area .
My bet is the spring that resists the needle movement is free to move or not adjusted correctly, (should not happen all by itself).
There may also be a 0 stop that may have broken off
I feel your pain.
When I pulled my cluster in late 22 I knew I should send the speedo out to have it repaired. But I did not and now I'll be pulling it this Winter
This is the speedo headUgh -thanks for that sad (bad) news! Is the 0 stop a physical "peg" on the cluster that stops the needle at 0 or part of the spring
This is the speedo head
View attachment 1716291634
Side shot
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Back
View attachment 1716291641
Green is the adjuster to correct the speed and the spring that returns the needle to 0
Red is the 0 stop
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Functionality
The part (red arrow) spins with the speedo gear and shaft in the speedo cable.
It causes the part it spins around to move. Since it is attached to the needle the needle moves. The spring resists the movement otherwise it would read 120 when ever the car was moving.
View attachment 1716291638View attachment 1716291636View attachment 1716291637
Any contact of the outer piece to the inner piece will cause the needle to be dragged farther than it should and when the co tact stops the needle rebounds to where it should be till the next contact.
That's one way you get a bouncy needle.
The other is a speedo cable that is sticking so it winds up a bit like a torsion spring then releases causing a speed increase at the needle.
That stands to reason. Buy unless it's been hacked in the past unlikely.
It could also be the needle on the shaft has spun a few degrees
As for 3-5 mph off unless it just started doing that at the same time the needle went south, I would say that's really good?
3-5 slow would be on the right track for the needle having spun in the shaft.The 3-5 mph drag started simultaneously with the needle drop