Vn800 meter how do i open the speedometer ? when i start driving the speedometer needle is stack and after a while it moves and show the speed, so i want to open it

the speedo meter is bad if ,odom works.
finding a spare that old is not easy
ebay used.

the actual speed is a Voltmeter , classical.
so the PCm sends speed this meter in voltage levels or pulses.
so if no VSS errors. send scanned then PCM (ECU) is ok
and the meter is bad or cable to it is loose or damaged.
a tech can even remove the meter and clean it. in the magnet inside
and the core my have metal dust stuck to it and jam it up.
i have repaired many and some are just warn out.

It could be a speed sensor which is a simple replacement or there could be something wrong inside the electronic control.

I would start with checking the VSS (Vehicle speed sensor) Usually mounted underneath car at the back of the transmission area.

Phylspilot, my 86 Spider never displayed less than 10 mph. If you look closely, you should see a tiny pin that the needle touches at about 10 mph. That prevents it from ever falling to zero. The needle will not move up until the speed exceeds 10. From my experience, that is normal. In your case, not displaying >20 is NOT normal.

The problem could be a few different things. Since the odometer appears to be working ok (I assume you checked that it racks up the miles at a rate commensurate with your approx speed), the speed needle may be sticking. I had the opposite problem with mine - speed needle okay, and odometer messed up.

I recommend pulling the speedometer housing out of the dash and checking to see if anything is causing the needle to bind. If it isn't, then check the fine spring where the needle is attached to ensure the spring is okay. You should be able to move the needle with your finger smoothly and have it return gently to the start position (in your case 12 mph).

This is a tricky operation. If you remove the needle from the stem, carefully place it back on the stem. Do this without moving the stem. Just reinsert the speed needle on the stem exactly at the small pin that holds the pin at about 10 mph.

Check the entire speedometer housing for cracks. Any crack could be enough to prevent proper operation. (That was the source of my odometer issue.)

Have fun putting it all back together.

Could be the speed sensor on the transmission or the speedometer on the dash. Does the odometer work ?

Try this. Turn the key on, do not start the vehicle. Absence the needle on the speedo. It should move down and then back up. Before it moves back up turn off the key. Repeat this until the needle is at zero. Then start the vehicle. If the needle goes back to a spot other than zero, you may have to take it for a quick drive, than the speedo head is likely bad. This is a pretty common an known issue for gm's. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com!

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Try this. Turn the key on, do not start the vehicle. Absence the needle on the speedo. It should move down and then back up. Before it moves back up turn off the key. Repeat this until the needle is at zero. Then start the vehicle. If the needle goes back to a spot other than zero, you may have to take it for a quick drive, than the speedo head is likely bad. This is a pretty common an known issue for gm's. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com!

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Thsi is likely a problem inside the speedometer guage internally with the driven gears. They use drive motors to drive the needles inside. If it is pretty continuous then the speedometer is in trouble and will require a speedometer specialist to rebuild the unit or replacement of the unit.

The speedometer drive and driven gears inside the transmission needs replacing

Check the speedometer cable if it is fitted correctly (from tyres to meter). In worst case open speedometer check the coil and try to give it a twist with your fingers. if the needle doesn't move a bit your speedometer has gone so you have to change your speedometer.