I/S Speedometer issue.....New one! SOLVED!

[Dr Bobs Patient]

OK, after searching for about 45 minutes for this issue, I have concluded that this may be a new tech issue.

First off when I bought my 99 IS this year, it came with a Show Chrome Touring windshield that I couldn't see over, so I decided today to cut it down 3".  That little project went real smooth until......

I went for a test ride.  I hit the highway and looked down to check my speed and the speedometer was registering zero!  I hit the tripometer and found that it was registering every tenth of a mile so I knew the gear, analog to digital transducer and cable were functioning. When I got to Wally World, and turned the bike off I saw this................

The speedometer needle had jumped behind the zero stop on the dial.  Apparently, when I was cutting down and sanding the edge of the windshield with my new handy dandy Milwaulkee Oscillating Battery Powered Tool, it must have jumped the stop!

Is there a way to open up the speedometer and corerct this?  And is it hard to get at?  Thank you in advance for yur help.

DBP

[olddog1946]

I believe the trick is to use a good strong magnet to pull the needle to the glass and over the post.

[JaysGone]

OK, after searching for about 45 minutes for this issue, I have concluded that this may be a new tech issue.

First off when I bought my 99 IS this year, it came with a Show Chrome Touring windshield that I couldn't see over, so I decided today to cut it down 3".  That little project went real smooth until......

I went for a test ride.  I hit the highway and looked down to check my speed and the speedometer was registering zero!  I hit the tripometer and found that it was registering every tenth of a mile so I knew the gear, analog to digital transducer and cable were functioning. When I got to Wally World, and turned the bike off I saw this................

The speedometer needle had jumped behind the zero stop on the dial.  Apparently, when I was cutting down and sanding the edge of the windshield with my new handy dandy Milwaulkee Oscillating Battery Powered Tool, it must have jumped the stop!

Is there a way to open up the speedometer and corerct this?  And is it hard to get at?  Thank you in advance for yur help.

DBP

Ive had simal issues with gauges where you cant remove the glass.
I have used a rubber mallet and tapped some times pretty hard to ge the neddle to jump over the pointer stop.

It is possible also to use a rare earth magnet such as in a dead hard drive to lift the needle over some of these devices. That would naturally be my 1st choice to try.

[Dr Bobs Patient]

Thanks guys for the magnet idea.  I'll try that.  The manual does show a procedure for removing and disassembling the meters.  That looks like a few hours worth of fun and games.

DBP

[da prez]

  I have removed many bezels (the ring and glass ) but if you do not have a new ring, you can reinstall the  0ld ring but it is not pretty. 10-4 on the magnet !
                                                 da prez

[Oyeaa]

You can open it up if the magnet trip does not work.  But you have to take apart the whole fairing and then the dash module under it.  I did this craziness for a very short while!  Major dis-assembly to change the face plate out, then back again later.

[Dr Bobs Patient]

First off I want to thank olddog1946 for the magnet suggestion....but it didn't work as suggested.  I looked around the house thinking now where can I find a magnet!  Then it donned on me that the security contacts have rare earth magnets so I disassembled one and borrowed the magnet from it.

I then turned the ignition on to get the needle up to the stop, but the magnet wouldn't budge it but just a little.  I then turned the ignition off and found that the needle ran from the magnet as in how two magnets when placed in the correct manner will repel each other!  So I was able to "chase" the needle counterclockwise back around to the correct position!  Problem solved without major fairing surgery!  I then took the old girl out for a test ride and all is well!

Thanks again for the suggestion olddog1946!

DBP

[Rio Wil]

Ya know......I can't deny your success in fixing this problem, but for the life of me, I can't understand how your method worked.  The needle is typically spring loaded to cause it to return to 0 and rest against the stop. How did it manage to find a resting point at about 320 degrees clockwise from normal.....why didn't the spring rotate it ccw back to the  0 stop?  I understand what you did with the magnet, but the initial out of positioning of the needle is still a mystery..

[JaysGone]

Its simple.
Lets just suppose the needle turns clockwise to show speed indication.
Its at rest at zero and fully unsprung when counter clockwise.
You beat on the fairing.
The indicator jumps a bit more counter clockwise but over the stop.
Now where do you suppose it going to go if its over the indicator but still at a full rest........???

Happens all the time to my to my dial pressure gauge in my saddle bags too.

Now of course none of this applies to the speedometer.
If its like most analog displays.
Its electromagnetic.

Except for the Valks which is mechanical.

[Ricky-D]

I don't feel the needle in the Interstate's speedometer is spring loaded.

I think it is totally electronically controlled.

Seems I have head of this same problem before with the same fix being the use of a magnet.

***

[JaysGone]

I hava a standard.
Isnt your display an LCD ??

[Daniel Meyer]

I've had the same issue...and fix (magnet) with a standard tach as well.

[Dr Bobs Patient]

I hava a standard.
Isnt your display an LCD ??

Hey Jay,

It's not LCD.  A needle like a standard.  What these other guys are saying about spring loaded and such is over my head.  I haven't torn a speedometer apart to see how they work.  I just stumbled across a fix to mine by accident.  Good karma I guess, or the gremlin bell is finally working!

DBP

[Rio Wil]

I don't feel the needle in the Interstate's speedometer is spring loaded.

I think it is totally electronically controlled.

Seems I have head of this same problem before with the same fix being the use of a magnet.

***

Ricky, that certainly appears to be the case given the circumstances with which it can be reset to zero.  I would have never guessed it was of that construction.  So, the standard speedo, which uses a mechanical cable vs a electrical signal, will respond to the same fix??  I can see how a tach on even a standard would respond the same since it is essentially a speedo, just operated with a different set of electrical rules.

[Ricky-D]

I'm not so sure the speedometers for the Tourer and Standard are like the Interstate on the insides.

Those are totally mechanical I feel, and are as you said, are controlled by a spring reacting against a turning magnet which in this case needs a stopping post to keep the needle from going into a negative mph mode.

I'll admit that the Interstate speedometer befuddles me as to exactly how it works and I just draw upon reports from others about peculiarities  and the fixing with a magnet.

I've done taken apart a few mechanical speedometers however - they're pretty straight forward.

***

[Gryphon Rider]

Here's what I know:  Electronic analog gauges (including speedometers) are actuated by stepper motors.  Stepper motors are designed to move in precise increments, rather than spin continuously.

Here's my guess at why the magnet worked to fix DBP's speedo:  Just like you can manually turn a small electric motor that is unpowered, you can manually turn a stepper motor.  The tiny stepper motor that moves the speedo needle is very easy to turn, and DBP was able to do this with his magnet.

Here's a photo I found on a electronics forum (http://forum.allaboutcircuits.com/showthread.php?t=31856) of a stepper motor for a Lexus speedometer (the motor shaft that the needle mounts to is on the other side of the circuit board; more photos are on the linked page):

[Rio Wil]

I suspect the following probably best describes the electro and mechanical components of our cable (standard) and electronic (I/S) speedo's:

The eddy current speedometer has been used for over a century and is still in widespread use. Until the 1980s and the appearance of electronic speedometers it was the only type commonly used.

Originally patented by a German, Otto Schulze on 7 October 1902,[2] it uses a rotating flexible cable usually driven by gearing linked to the output of the vehicle's transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel.

When the car or motorcycle is in motion, a speedometer gear assembly will turn a speedometer cable which then turns the speedometer mechanism itself. A small permanent magnet affixed to the speedometer cable interacts with a small aluminum cup (called a speedcup) attached to the shaft of the pointer on the analogue speedometer instrument. As the magnet rotates near the cup, the changing magnetic field produces eddy currents in the cup, which themselves produce another magnetic field. The effect is that the magnet exerts a torque on the cup, "dragging" it, and thus the speedometer pointer, in the direction of its rotation with no mechanical connection between them.[1]

The pointer shaft is held toward zero by a fine torsion spring. The torque on the cup increases with the speed of rotation of the magnet (which is driven by the car's transmission). Thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. The cup and pointer will turn until the torque of the eddy currents on the cup is balanced by the opposing torque of the spring, and then stop. Since the torque on the cup is exactly proportional to the car's speed, and the spring's deflection is proportional to the torque, the angle of the pointer is also proportional to the speed. At a given speed the pointer will remain motionless and pointing to the appropriate number on the speedometer's dial.

The return spring is calibrated such that a given revolution speed of the cable corresponds to a specific speed indication on the speedometer. This calibration must take into account several factors, including ratios of the tailshaft gears that drive the flexible cable, the final drive ratio in the differential, and the diameter of the driven tires.
Electronic

Many modern speedometers are electronic. In designs derived from earlier eddy-current models, a rotation sensor mounted in the transmission delivers a series of electronic pulses whose frequency corresponds to the (average) rotational speed of the driveshaft, and therefore the vehicle's speed, assuming the wheels have full traction. The sensor is typically a set of one or more magnets mounted on the output shaft or (in transaxles) differential crownwheel, or a toothed metal disk positioned between a magnet and a magnetic field sensor. As the part in question turns, the magnets or teeth pass beneath the sensor, each time producing a pulse in the sensor as they affect the strength of the magnetic field it is measuring.[1] Alternatively, in more recent designs, some manufactures rely on pulses coming from the ABS wheel sensors.

A computer converts the pulses to a speed and displays this speed on an electronically-controlled, analog-style needle or a digital display. Pulse information is also used for a variety of other purposes by the ECU or full-vehicle control system, e.g. triggering ABS or traction control, calculating average trip speed, or more mundanely to increment the odometer in place of it being turned directly by the speedometer cable.

Another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsator driven by the car's wheel or transmission. The watch mechanism endeavors to push the speedometer pointer toward zero, while the vehicle-driven pulsator tries to push it toward infinity. The position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms.

[Dr Bobs Patient]

After reading the above explanation, why do I feel like I just walked into Leonard and Sheldon's apartment?

DBP

[Rio Wil]

How does that go.....BAZINGA!   

[sugerbear]

got the t-shirt.

[Rio Wil]

I just bought my grandson the one with progression from ape to man to robot.....he is a bright little twirp!