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Odometer Question


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I have seen a lot of talk regarding the accuracy of the speedo but I have had a problem with the odometer increasing without the car leaving the driveway.

During the build phase pushing the car out of the garage onto the driveway a number of times caused in excess of 10 miles to be added (over three different units that were exchanged by Caterham).


Caterham confirmed there is a known problem with the instrument where it may be related to reading 10ths of a mile and rounding up each time the ignition is powered up. -I have even seen the mileage increase with the ignition on and the car stationary.


I am surprised that I haven't heard of this before if it is true as Caterham say that all cars will do this.


Have any others had this problem ? - are there any workarounds to correct this ?


It worries me that over the life of the car the odometer could become very significantly out.



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I'm not an expert with electrics, but, would it not be possible to have a direct feed to the speedo (with an in-line fuse of course), so the speedo was always 'on'. (Of course you would need to use of Optimate or similar when the car was not in use, to save a flat battery).


Just a thought, might be a pants idea 😳




Simon Emmens Caterham and Pussy Photos here 😬

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Intersting thought !


I have an Optimate for my bike and plan on putting a power socket in once the car's back from SVA. - I might just experiment over the first couple of weeks to see if there is any difference !

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Call me naiive but I am almost shocked to hear this! "They all do that" Do they? Is this a Seven problem or do all car/gauge mfrs. have this problem? Not that I'm any kind of expert, but I've never heard of this behaviour before.


Coupled with the speedo's inaccuracy adding mileage and this behaviour, how can anyone be sure of the mileage of a vehicle.



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Caterham did tell me a few weeks back that they were having discussions with the manufacturer to resolve the issue. However last week when dropping the car off for it's post build check I asked if they would be fixing it. The response was basically "the all do that" with no further comment.


As I managed to clock up greater than 10 miles working on the car in the evenings over a couple of weeks by simply moving the car about 1 1/2 car lengths (once each day) I am reluctant to ignore it.


I should be picking the car up at the end of this week, when I shall be pushing the matter again.


The rounding issue mentioned previously is one thing but to see the mileage increase with the ignition on and the handbrake on is another. eg does it do this all the time the ignition is on ??? (over and above the mileage it should be clocking up!)


Anyone recall the similar Peugeot 307 issue ?




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mine did it and Caterham sent out another speedo head under warranty - which also did it. Fairly safe to say that they all do that.


I wondered if the type instrument was originally designed to be on a permanent live feed i.e. displaying the odometer lcd reading all the time rather than when the ignition is turned on and it's just the Caterham installation. You would hope that a branded i.e. bespoke gauge would be correctly wired though.


Wait 'til you discover that the car doesn't turn off immediately when the radiator fan or the heater fan is running due to the back emf from the motor, or you hear that the fuel system 'moos' gently when the tank is nearly empty even after the engine is turned off, or you can hear the IACV whistling after the engine is turned off........






Green and Silver Roadsport 😬

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Since I have not fitted the speedo sensor to mine car yet I got it on the bench and did some careful investigation with a power supply and a scope. With the Blue/red lead grounded and the green lead taken to a 5v current limited supply via a 1k resistor I found I got 8 pulses for every rev of the sensor (the pulses were about 3v high). I guess from this that the sensor is a hall probe and some magnets. I think the method could be quite susceptible to electrical noise. The wires are not screened and run in the loom along with lots of other wiring so its quite possible that the odometer is adding up any spikes from the ECU, the indicators, your mobile phone etc. I can't see anyone going to the trouble to code in a rounding function to the unit just so it can cause this problem!


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