I've done some searching and am struggling not to feel too worried, but my speedo suddenly started acting up today.

Initially, it stopped working below about 25 mph, where it would drop like a stone to zero. Above that it seemed OK. Hoever, after only a few miles it was getting worse - sticking, jumping, waving around.

Maybe this is wishful thinking, but when I've seen this before on other cars it has been the gauge itself, although I could believe it might be a sender problem.

Obviously I'm hoping it's not the speedo gear, although this is a DCA recon box and less than two years since fitting.

How can I diagnose the problem?

does your cruise con work ok ? cus if so then its probably the clock not the sender

does your cruise con work ok ? cus if so then its probably the clock not the sender

Don't have cruise. I do have an SCC, but I think it will be hard to figure out from this, unless I figure out which is the speed signal on the connector and hook a scope to it.

not quite the same symptoms that I had, because when my speedo flickered & died the engine would cut out as soon as I took my foot off the throttle (even between gearchanges). that was due to a wire to a sensor underneath somewhere that my local garage had dislodged when replacing my crank sensor. just needed soldering back on in my case. I had the same speedo-drive panic as you.