Erratic / non-working speedo when HOT

[Guest]

Hi All

 

Over the last few weeks I've noticed the speedo can be a bit erratic. This only happens on warmer days when everything is nice and hot. The speedo fluctuates by maybe +/- 10mph, but only some of the time.

 

Last weekend, with it being very warm on the Saturday, not only did it fluctuate but then stop altogether! I stopped at a friends for a cuppa and by the time I came out (30 mins later) it was working again, although within 3 miles or so it happened again.

 

So it certainly seems heat related. Does the wiring run close to the exhaust manifold? Has anyone else had this whereby heat appeared to be the root cause?

[Stationary M25 Traveller]

Do you have the type of speedo with the sensor pickup on a rear wheel ? Maybe air gap incorrect or wiring chafed where it is cable-tied to the chassis tubes.

[Garry7]

Hi Grant,

It's a known fault, CC have issued a workshop update for it.

Recommend you call James in aftersales dept at CC. [: it's happened on my car and was driving me mad - didn't need it on the trip to the Classic and back.

[IanW]

Also, check your earth leads. I had a similar problem that resolved itself after the earth straps in the engine bay had been re-seated.

 

[Guest]

Thanks all,

 

Need to jack the car up to check (need a low enough jack first!).

 

@Garry7 - James is in 'aftersales'? It that service?

 

Will monitor over coming days and report back.

 

Thanks all

[Garry7]

Hi Grant,

 

Sorry, yes he's the service mgr at Dartford.

 

Garry

[Martin J]

Need to jack the car up to check (need a low enough jack first!)

 

How over height is your trolley jack? I find with mine if I push the car up onto a couple of pieces of wood perhaps half inch thick, the trolley jack fits under the A frame bracket perfectly.

[Guest]

Hi Grant

Mine does the same! Cleaned sensor and usual suggestions but no cure.(sigma with rear offside wheel speedo sensor) Always felt erratic nature and eventual zero reading of speedo was temperature related. Returns to normal once all cooled down only to become erratic once temperature back up! Will keep eyes on this thread to see suggestions for cure and start tinkering when I get an hour or ten!

Jim.

[Guest]

Hi All

 

So this evening it's a bit cooler than last weekend. I'm just back from a 40 mile blat, including plenty of, ahem, full-throttle work ( 😬), and the speedo has worked perfectly.

 

I shall keep monitoring it http://www.jonrb.com/emoticons/detective.gif

 

[john milner]

I've had a speedo intermittently not working for two years and until reading this it has never occurred to me that heat may be the issue. Three times this week I have made a six mile trip from cold with no problems then left the hot car in the sun for an hour or two (half hood up) only to have the speedo not work for about five minutes coming home. I'm pretty sure it has only ever played up in the Summer so I doubt the gearbox end is at fault as that will get hot even in the Winter so am now wondering if an overheated speedo is the cause. I've lost 2-400 miles out of the last 15,000.

SV body, K series, type 9 gearbox, standard Caterham gauge.

[Guest]

I've just been out in this evening's heat but only did circa 12 miles (blame my lame-o wife). At the end of the 12 miles it was slightly erratic but nothing more. Will continue monitoring and report back

[Guest]

So in last night's heat (loving this blatting weather at the mo ) I did a good 30 miles out and about and yes, the speedo was intermittent.

 

One thing I have noticed is that when it starts to become erratic, braking hard will cause the needle to drop to zero and then a small application of throttle will bring it back to life