Speedometer failure----any similar experiences?

[Logan Colbeck]

During a blat this afternoon, my speedometer stopped indicating and stopped logging miles driven, though it did display the accrued mileage and the trip mileage. It is a two year old Duratec with about 6700 miles on the clock. 

It was very muggy at the start of the blat, and there was condensation in evidence on body and engine . 

Any views, before I start taking things apart?

Many thanks for any contributions!!

Logan.

 

[SM25T]

Probably the type with the sensor located on the offside rear wheel. Check gap. Think led on sensor that flashes each time it sees target. Lift the rear of the car and turn that wheel with ignition on.

[Jonathan Kay]

What Ian says.

There are three common types: mechanical from the gearbox, electronic from the gearbox, and electronic from a wheel. First have a look and tell us which it is.

All other instruments and electrics working normally?

Jonathan

[JNC]

I would think it's a rear wheel sensor, Hopefully a two year old car will already have the earth mod done to the sensor ! It's worth checking. 

 

[Logan Colbeck]

Many thanks for these comments. I have removed the rear wheel and spotted what appears to be a chafed insulation to the sender cable. I have removed the sender and it's plug to the loom which is a three pin connector.

My working assumption is that the chafing is responsible for an electrical short and I need to replace the sender and cable.

Problem------it's not listed as a CC spare. If any of you kind folk know of a source, or can guide me to a replacement, I would be most grateful.

Thank you for responding so promptly!!

Regards, 

Logan.

[Jonathan Kay]

Replacement part.

And the same thread links to the Caterham workshop notice on a modification for improved earthing.

Ian's described the method of testing: there's also more on that, and somewhere there's a note on making a spacer if needed.

Jonathan

[Logan Colbeck]

Many thanks, Jonathan. I shall contact CC on Monday. Really grateful for the advice!

 

logan.

[SM25T]

This chafing is too common. Has often caused the car to be immobilised .... we have seen it happen on cars a long way from home. I hope CC take some responsibility on your car !

[Logan Colbeck]

That is interesting SM25T. I have tried to start my car after removing the sender, but it will not! Do you have any other information on this effect, as I was planning to drive it with the satnav as a speedometer.

 

Best wishes,

 

Logan

 

 

[SM25T]

I think it takes out a fuse in the main fuse rail. Replace that once sender unplugged and all should be well

[JNC]

Don't take much notice of the fuse diagram in the hand book  ! Mine is wrong , you may be lucky but if not work your way through the fuses.

[Jonathan Kay]

It is a two year old Duratec

​Don't take much notice of the fuse diagram in the hand book  !

Have you got an Assembly Guide and Handbook? If not send me a Private Mail with your email address. And if you have a type that doesn't match we'll work it out and document it to help the next victim.

Jonathan

[Jonathan Kay]

 I have tried to start my car after removing the sender, but it will not!

 I think it takes out a fuse in the main fuse rail. Replace that once sender unplugged and all should be well

Has anything else failed at the same time?

If it turns out not to be the fuse have you got a multimeter?

Jonathan

[JNC]

JK , apparently it's a well known problem,  When I changed the sensor and did the earth mod a fuse blew and mine wouldn't start . Apparently if the sensor fails it can blow a fuse that will make the car fail  !  I now always carry some spare fuses . If the sensor fails the fuse can be replaced and the car will start and run fine but the speedo won't.

[SteG]

I had exactly the same problem this summer on my 3 year old roadsport. Speedo / odometer stopped working. Rear wheel sensor was eventually found to be at fault. Carried out the earth mod, (probably already done on your car) fitted new sensor and been OK since. The sensor is on the CC website it's just a b*gger to find it. Best part of seventy quid though. As all have said before, the sensor gap is critical and make sure it lights up on each castellation for a full 360 degree turn.

[John Vine]

The sensor is on the CC website it's just a b*gger to find it.

For those still hunting, this is the little fella.

(ETA on 23 April 2018: The sensor linked to above no longer appears on CC's website.  This one (300A0019A) looks its replacement.)

JV

[Logan Colbeck]

Greetings to all of you who have help me. I have located the blown 7.5 amp fuse caused by the failed sender and replaced it----first unplugging the coupler behind the rear wheel as recommended by JK. The engine started immediately as predicted in two of the earlier posts!!! I have contacted CC and they are to send me a new sender overnight. So I should have a resolution to all of my issues in the morning! 

So, with the combined input from techtalk and CC, I have a resolution within three days. But, more importantly, I now know that the sender is classified in the fuse system as an instrument, and once the fuse goes, so do all associated instruments, including the engine running permissives!

I have sourced a couple of spare 7.5 amp fuses for my tool kit in the car and would commend this action to all owners with electronic senders located at the rear offside wheel.

Many thanks to all again!!

Logan.

[Jonathan Kay]

Well done.

I have sourced a couple of spare 7.5 amp fuses for my tool kit in the car and would commend this action to all owners with electronic senders located at the rear offside wheel.

An alternative would be to use a circuit breaker that you push to restore. (But I carry a selection of ordinary replacement fuses all the time.) And then there are those blade fuses that light up when they're blown.

Jonathan

[Garry7]

It's not just the Chafing, they are prone to internal shorts too. Mine died in Luxembourg on days 2 of a 10 day tour. Disconnection, replacement of fuse 4th from the top and back on the road. Too expensive to carry another just in case. My 4.5 year old Duratec is on its 5th sensor. Y

[Ivaan]

How about wrapping the sensor and cabling in self amalgamating tape to give it some protection?

[Jonathan Kay]

My 4.5 year old Duratec is on its 5th sensor.

Why do some suffer more than others?

Jonathan

PS: At that frequency I'd definitely replace the fuse with a resettable circuit breaker and/or run the sensor through a fuse of it's own, probably using one of those clever little piggyback fuseholders.

 

[JNC]

@ JK ,  I'm not sure but  I think it's a protection device ! The engine sees a sensor failure it doesn't know witch one so fails safe . Someone will be along soon and either agree or tell me otherwise  ?

[babymerc]

My sensor failed after just 57 miles on a new build. Luckily, Caterham exchanged it under warranty.

[JNC]

Met up yesterday at Goodwood with a few lads from Surrey and East Sussex for breakfast,  One of the chaps had lost all instruments on the way ! He was busy under the bonnet having a look around for loose wires, I asked him if his speedo was working ok before the loss of instruments  !! Guess what he told me no it was very erratic then it stopped working and realised a bit further down the road none of the gauges were reading . He tried replacing the fuse and it blew straight away, unfortunately he had done a very good job at securing the plug to the sensor with ties and couldn't disconnect it ! . When he got home and cut the ties and unplugged it, he renewed the fuse and all the gauges came to life except obviously the speedo . 

When will CC sort this problem ? They are aware of it and the last time I asked they were trying to source a different sensor !! .

 

[John Vine]

Well diagnosed, John!

Interesting to hear that CC's solution appears to involve sourcing an alternative part rather than addressing the basic design problem.  About 10 years ago, much the same thinking led to the adoption of the SKF clutch release bearing over the INA one.

JV