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speedo drive


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Looking at Build Manual....... "The brass 'top hat' should be located over the oil seal and held in place by the circlip. Ensure that the circlip is fully located into the groove as access is restricted when gearbox is in car. Do not fit the sensor. ( Because you would break it off when fitting gearbox in car) As mentioned previously check sensor and speedo end contacts. Sensor end should be under rubber plug under tunnel carpet drivers side roughly level with hand brake handle so you will not have to get under car. Use some WD40 on connectors or better still Maplin Switch cleaner spray.

If no luck then trouble may be under the "top hat" where the sensor is mounted. Hope not as probably gearbox out job. There is a tiny little metal drive about 1 1/2 inches which rotates from gearbox under the "top hat" and turns the sensor. I had this problem once and it did not work after pushing connectors on and off at both ends and then suddenly it started working on a journey the next day and has worked OK for past 5 1/2 years !! Also from Manual..... "screw the speed sensor onto the "top hat" ensuring that the drive cable slots into the speedo gear output shaft" so check that sensor has not become unscrewed so little drive is not in its slot.. Don't what else to suggest if it still doesn't work... Faulty sensor or speedo?

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Think you must have an old Caterham. Speedos don't have cable drives any longer. They are electronic and use wires. The only "drive" on the modern ones is a length of "cable" about 1 and 1/2 inches long under the "top hat" to the sensor and could not suffer from wind up. It could suffer from the sensor becoming unscrewed and the "cable" failing to turn the sensor like if the old cable ones were not screwed up tight behind the speedo head or the gearbox end.

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