Speedometer Falls to 0 above ~80mph

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robsandbach
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Speedometer Falls to 0 above ~80mph

Hello everyone,

I wondered if more experienced members could help me triage this issue based on the following symptoms:

- Speedometer is calibrated well and works as expected up to around 80mph

- At, and above, 80mph the needle falls to 0.

- When speeds return below 80mph the needle kicks back into life and reads accurately again.

I'm completely new to this side of car ownership so even some basic areas to look at or tests to run would be much appreciated!

Thanks,

Rob

Jonathan Kay
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Private Message sent.

Jonathan

ScottR400D
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If it's the sensor on the rear driveshaft type, it's almost certainly the adjustment of the sensor gap. Many of us have had the issue and solved it by moving the sensor slightly closer, or slightly farther away from the toothed ring. 

 

 

robsandbach
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Thanks Jonathan, I really appreciate the quick reply!

Some requested details it is a 2019 Academy Car with the 1.6 Sigma. Speedometer shown below:

 

Thanks!

Rob

Geoff Brown
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Happened to me all most exactly - first time the sensor was faulty & changed out + earthing mod fitted. Second time adjusted new sensor - all OK.

Before you adjust the sensor clean the exciter ring teeth with a tooth brush & WD40. Helps.

ChrisC
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Being a 2019 car it should be a new style sensor (not show in even the latest release of the build manual last week).  This new sensor likes to sit a bit closer to the trigger wheel than the older sensor. 

As already advised I bet this can be solved with a combination of cleaning, gap setting and earth moding. 

If it fails at 80mph its possible that its always been like that, its only tested up to 70 mph during the IVA test, and most onboard footage I have seen from academy races have the speedo disconnected. 

If it helps this is the new sensor and earth mod fitting 

https://caterham420detailedbuildblog.co.uk/2020/01/25/speed-sensor/

and this is how I tested it 

https://caterham420detailedbuildblog.co.uk/2020/03/12/speed-sensor-testing/

 

John Vine
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Sounds like a problem with the sensor air-gap.  Have a look at this Guide.

JV

Wrightpayne
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Great excuse - my speedo said I was doing zero Hofficer!!

Mark w
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Its almost certainly the sensor gap , try reducing it a bit to start with .