Speedo Repair

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RPinAZ
United States of America
Posts: 21
Joined: Sat Sep 26, 2020 7:04 pm

Speedo Repair

Post by RPinAZ »

My speedo was very consistent - the trip meter didn't work, the odometer didn't work and the speedometer quit working as well. (The light may not work either, I haven't checked it yet.) The speedometer needle would go all over the place, then go to zero, then come to rest at about 40 km/h when I stopped. It never would return to zero.

I managed to get it apart based on the instructions in the Tech Sessions and I fixed the odometer and the trip meter (the cog was slipping on the driven shaft as is typical). Nothing I tried would fix the speedometer though and I couldn't find any posts that addressed it directly. Each time I put it back together and tested it by spinning it up with a drill, it would go nuts again. I was about to give up and order an electronic speedo, when I noticed that there was a lot of clearance between the square drive where the drive cable plugs in and the housing - about 1/8" of clearance. I had already separated the drive portion from the tripmeter/odometer portion, so I pushed in on the magnetic wheel that the drive turns and holding it in place, I pushed in on the square drive and it appears to be a light press fit on to the magnetic wheel - it slowly pushed in and eliminated the clearance. In the picture below, the red arrow shows where the clearance was. The picture shows what it should look like, i.e. no clearance.

Here's what I think was happening. When the square drive end slightly separated from the magnetic wheel, it allowed the magnetic wheel to shift aft enough that it no longer supported the rear pivot for the speedo indicator shaft. With the aft pivot not supported, it allowed the cup that drives the speedo needle to intermittently drag on the magnetic wheel causing it to move erratically and preventing it from returning to zero. Once I pushed it back together to eliminate the clearance, it worked great.

As a side note, I had several scratches in the plastic face of the speedo. I found that metal polish (I used Wenol, but others may work as well) took out every last scratch - it took about an hour of polishing, but it all came out.

-RP
Attachments
Speedo.jpg
Speedo.jpg (253.01 KiB) Viewed 2455 times
Speedo2.jpg
Speedo2.jpg (685.73 KiB) Viewed 2455 times
boeing7873
Argentina
Posts: 197
Joined: Sun Dec 21, 2008 10:50 am
Location: Atlanta
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Re: Speedo Repair

Post by boeing7873 »

Excellent! Mine works but is not accurate, both from wheel size change and from a previous repair. Trip does not work either... I think I am giving up. Must chose the projects.
Jerome
CRJ Driver
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