Speedometer Not Working, but Odometer Is

[colnago]

All,

I have an F600 cluster in my '67 F250. The other day, my speedometer stopped working, but the odometer continued working. So, it's definitely in the speedo itself, and not down by the transmission. Any pointers on what happened (and how to fix it)? This isn't anything too major, but it sure is annoying. I've never bothered to learn anything about speedo internals, since I haven't needed it.

Thanks,

Joseph

[Mach428]

You will obviously need to pull the cluster and look at the back. The speedometer uses a magnetic drive for the speed and gear drive for the odometer. I would bet that once you remove and inspect, the fault will be obvious.

[colnago]

Well, I found out what the problem is, but not the solution, or why it is happening now. The speedo cable comes into the unit, and goes directly into a shaft. The shaft has a screw-drive for the odometer, then the end goes into two flat arms that have the magnets. They are resting over a metal cup that drives the speedo needle. The faster you go, the more magnetic influence you have that don't let the needle drop back down. No physical connection between the magnet arms and the needle cup. Sorry, bad description; I'll have to take a photo next time I open it.

Anyway, the magnet arms are rubbing on the top rim of the needle cup. There's a bit of slop in the input shaft, so I can manually push them in and make them rub against the rim. I'm not sure if something wore, or if it's something else. I don’t see any broken parts, or any sign that something was lubricated and is now dry. I dunno, but if anyone has any ideas ...

Thanks,

Joseph

[takehikes]

I have the opposite problem, speedo working but not odometer. Anyone have any ideas? I've never dealt with this before.

[Ranchero50]

I have the opposite problem, speedo working but not odometer. Anyone have any ideas? I've never dealt with this before.

Same deal, take it apart and figure it out. They are pretty neat to work one. All mechanical with little gears driving the wheels.