All Vanagon speedometers will eventually fail and need to be replaced. This article outlines the different speedo types, why they fail, and how they can be replaced.
There are four different Vanagon speedometer types for vehicles delivered in the USA. The 1980-82 unit has a speedometer cable that screws onto the back. The 1983-85 type has a cable that snaps into the back. The 1986-91 2WD speedometer also has a snap-in cable but also has an electrical circuit built in for the low oil pressure warning buzzer and light. Finally, there is the 4WD Syncro type that is identical to the 1986-91 2WD speedo, except the face has the calibration number "1600" on it instead of "800-something" like on the others.
The speedometer is actually two instruments in one, indicating both vehicle speed (speedometer section) and distance traveled (odometer section).
All these speedometers fail in one of two ways:
Either it indicates speed and not distance traveled (most common failure), or the odometer works but no speed is indicated (less common). If your speedometer does not indicate either, it is probably a problem with the cable. Remove the cable from the back of the speedo and if you see the cable is not spinning, replace the cable. If speed is being indicated but the odometer does not move, there is definitely something wrong with the speedometer itself. This is the most common failure. There are several plastic gears involved in the odometer section, two of which have proven to be unreliable. When one of them fails, no more distance indication. If the odometer works but there is no speed being indicated, there is definitely something wrong with the speedometer itself. In that case, there is usually dirt and/or corrosion that is making the needle stick. Sometimes banging the dashboard on the top while traveling above 40 mph will make the needle jump up and work.
For many years, we offered an exchange program where we would rebuild broken speedometers. We no longer offer this service. We now only offer our brand-new modern GPS Speedometer Kit. It is less expensive, highly accurate, and no longer relies on failure-prone cables and gears. Welcome to the future!