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Crazy Speedo

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DesertSprite

Jedi Warrior
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Hello,

Okay, so what exactly is going on when your speedometer does a 360 and pins itself against that little post as soon as you start off on your drive?

When I got the car, the speedo needle wasn't attached. I just put it back together today and it did the action described above. /ubbthreads/images/graemlins/confused.gif

Joel
 
When you put the needle back on did you line it up with the dot to the right of the zero post? That is the correct position for re-installing it. As Spritenut suggested the works could have been frozen at a point past zero and now it doesn't have enough tension on it and goes all the way around. Now that it is loose reattach the arm correctly and see what happens.
 
Biff,

I'm not sure what you mean by the "dot to the right of the zero post." Wouldn't you want the needle to the left of the zero post? I put the needle on to the left of the zero post so it would be able to rise as speed increased. Wouldn't the post block that from happening?

I'll try to re-attach it tomorrow and let you guys know what happens.

Joel
 
Joel,

There should be a 'dot' just to the right of the post or at least there was one there when new. That dot will put a little tension on the spring inside the speedo when the arm is at rest, i.e., on the pin. Without this small amount of tension it will never read correctly. Use that dot to align the arm and after seating the arm lift the tip up and over the pin.
 
The dot should be slightly counter clockwise from the stop post. However, this is a moot point.

If the needle has pegged to the right as soon as you started to drive the car, it's very likely that the hair spring is toast. This usually happens when the needle bearing on the back/bottom of the post supporting the needle drags. This is usually a bad thing. The only proper fix and answer is to tear the gauge down and carefully clean and examine the parts.

Do a Google search for the 27 page PDF by Anthony Rhodes regarding repair of Smiths & Jaeger speedometers. Print that out and use it as your guide as you disassemble your gauge. (Take pictures also). If the hairspring is ruined... buy a used gauge off of eBay or elsewhere and start over. When buying a used gauge, make sure the same 3 to 4 digit number stating the turns/mile is near the odometer window so it will work with your car.
 
Thanks Doug. I think your diagnosis is correct. I tried putting the needle back on in alignment with that little dot to the right of the post, and it still goes 360 degrees clockwise and pegs it as soon as I start to drive.
 
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