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Taped_Finger
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Speedo - Trigger Wheel

Wondering if someone is able to help me with the issue I am having with the speedo on my 310R.

When the speedo reaches about 70mph it starts to stutter then as I increase the speed the speedo just gives up and drops to zero, once I lower my speed to below 70mph the speedo springs back to life.

When I build the car in 2020 I installed the speed sensor with the earth modification wire to the rear ARB mounting bolt.

Not sure if it's the actual speedo causing the problem or the sensor, I've had a look at the sensor tonight and all looks fine and I'm getting the light beam switch on and off when I rotate the wheel.

Any ideas what it could be?

Thanks

David

Jonathan Kay
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That aberrant behaviour with high speed has been observed a few times. Even though the indicator light is working OK I'd suggest resetting the gap.

Previous discussion of gaps.

Guide on "Speedometers"

Jonathan

Taped_Finger
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Thank you Jonathan, I'll have a play with the gap

Taped_Finger
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Having another look at the speedo sensor, it actually looks like the prop shaft may not be seated correctly.

As the sensor is only covering half the teeth face

It's just come back from a Caterham dealer after a service, great!

This asks the question why has the prop slipped out the diff?

 

 

ChrisC
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The trigger wheel is known to move on the tripod joint.  Caterham replace the driveshaft if this happens under warranty, after all its a part suppliers problem (GKN).  If your car is under warranty contact Caterham, if not then consider cleaning the rust, applying some strong Loctite and pushing it back into position. 

As how I know

SM25T
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PS .... as above... drive shaft, not prop shaft
Taped_Finger
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My bad on the wrong part naming Whistle

I've spoken to Caterham as it is still under warranty and will wait and see what comes back.

Chris - Has your issue occurred on your latest build?

 

ChrisC
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Yep, this is a picture of my 420R.  It happened at the first proper dry track day, where I assume the driveshaft got hot from the disc.  It's a 2020 registered car, but the kit was supplied October 2019.  Apparently GKN now apply some form of green substance to secure the trigger wheel to the tripod joint, I wonder what that could be :-). 

Took as week to confirm the course of action (replacement driveshaft), but I am still waiting for parts.  That said I am not in a rush, I pushed the trigger wheel back into position to get a working speedo.      

ScottR400D
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Any idea when this became an issue Chris? I don't recall having heard about it until relatively recently? 

ChrisC
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It seems to have started sometime in 2017 (ironically when the new sensor was released).  I know of one fellow builder with a 2020 delivered kit that had the issue.  So sometime between 2020 and 2021 the fix has been applied by GKN. 

John Vine
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Once I get my engine back in, I'll turn my attention to updating the Speedo Guide to include the above problem.

If GKN are CC's official supplier of driveshafts (CC Parts are reticent on this point), has anybody asked them if they can supply spare reluctor rings?

JV