I have Mitsu instruments dating back to the early 70s and routinely find them needing lubrication.
I also replace the faces with a 180 MPH display and recalibrate them for accuracy through the new range. I know these units better than anyone who just says replace it.
wow! that kicks <img src="/forums/images/graemlins/butwiggle.gif" alt="" /> !
I am impressed as i can say the same also.
Quite a number of cable drive gauges have hydraulically dampened needles, generally tachometers. Of course I learned about these due to them not being stored in the proper position for a decade or two. Easy fix once they are opened up.
Oh I am sure professionals would say they are not rebuildable since they are crimped housings.
Even the newer elctronic instument clusters have fluid in the movements (jaguar , ford , etc). if you leave the cluster on its side it will cause a failure of the whole cluster! <img src="/forums/images/graemlins/frown.gif" alt="" />
I have heard that cars with these types of cluster are prone to fail if the owner parks the car a lot on a steep incline.
I didnt think the calibration would be significantly affected by friction. Meaning that the rotating magnet generates a current in the non magnetic disc that attached to the needle. That also generates a torque on the disk. That torque is resisted by the springs on the needle assembly.
The faster the magnets spin the greater the EMF in the disk, the greater the TQ, the higher the needed reads. Since calibration does not rely on friction, I'm not sure how lube would change the reading by a factor of four.
I have never seen an explanation of how a analog speedometer is supposed to work, but that's what it looks like to me. Did I miss something?
Kevin
One of the most common problems i see with the japanese made speedometer sysytem is when the Speedometer will read 80 or 120 mph when the vehicle is traveling much slower.
the speedometer just goes to full scale right away as soon as you get going.
this is because tranny fluid has worked its way past the gear and seal and up the Cable & Housing into the back on the speedometer.
The fluid is forced into the lower frame and infects the rotating magnet. this oil now is the " friction " .
Since there is no longer air between the speed cup and magnet it grabs the cup and flings it up.
If rebuilt properly we would seperate the collar from the magnet shaft and clean everything up nice. then we would GREASE the bushing with light grease. We would only add ONE tiny little drop of clock oil to the speed cup where it rides in the magnet and put it back together and be done.
just one tiny drop of oil and a finger full of grease!
and that is why i am warning against putting " Too Much " oil in the speedometer. it would suck to have to pull it all apart later because you went crazy with the oil gun.
and believe me i have seen speedos where people did just that. <img src="/forums/images/graemlins/scared.gif" alt="" />
