What causes speedo/tach needles to return to 0

[95Xsport]

Reason I ask is because I was doing this fix: LINK

I got to the part where you connect the battery back to the gator clips and set the speedo needle back in. I did that step but when I disconnected the battery, the needle either drops slowly and never makes it to the stop or it just says frozen and doesn't drop at all. If I push the needle down to the stop with my finger and connect the battery again, it will go back up to the correct speed but will again stay frozen or not move down much.

Before I dug into the odometer, the needle would drop back to the bottom just fine.

I'm not familiar with how the needles work but what causes the needle to drop? Any idea what would stop it from doing so?

 

[rs2k]

I would guess a hair spring. Maybe the back of the gauge is too tight now.

 

[bill06447]

I would guess a hair spring. Maybe the back of the gauge is too tight now.

I second that. Check your steps. After watching the tutorial I would guess the needle is pressed on too far, or the shaft was tweaked pulling it off....

Bill

 

[95Xsport]

Yeah I went through the steps trying to figure out if I remember anything but it all went smoothly and I don't recall a moment where I would have messed anything up.

Is there a way to remedy the issue if it is in fact the hair spring?

 

[rs2k]

You'll have to pull it apart again to get to the spring if that's the problem.

 

[koda2000]

i don't believe there's any springs involved. it should all be electromagnetic. i'd guess it works by something creating/adjusting a magnetic field to pull the needles up. perhaps there's some residual magnetic field that's remaining after the key is turned off. do the gauges function properly when the engine is running and you're moving?

 

[rs2k]

They are either stepping motors or eddy current meters. If they are stepping motors then there won't be a spring and the problem is there is probably something causing the needle to bind... in which cause you need to open up the panel and take a look.


If the gauges are calibrated eddy current meters then there's a spring that keeps the needles at 0 and the tension gets stronger the farther away from 0 the needle goes. There's a spinning magnet that creates more torque on the needle the faster it moves. There's probably something causing the needle to bind... in which cause you need to open up the panel and take a look.

 

[95Xsport]

I do still have the gauges apart. I haven't tried it in the car yet. Maybe that would help sync everything up again?

The only other thing I can think of is the screw driver I was using was magnetic. I don't remember touching anything other than the screws themselves but if I did touch the speedo motor with it, could that mess things up?

 

[koda2000]

yeah, i think until you put power to the gauges the needles will not behave normally.

 

[95Xsport]

yeah, i think until you put power to the gauges the needles will not behave normally.

Well you were correct!
I put the cluster back in today and everything worked fine. Maybe the needles are different on 95-96's but the how-to videos I saw of people reattaching their speedo needles in 97-01's all showed the needle falling back fast, which worried me. Guess I didn't have anything to worry about though