kevinrooney wrote: At one stage mine jumped to 180 mph clocked up nearly 80 miles on the mileometer over a 2 mile journey .
Whilst checking out some info for myself, I came across this interesting post, with a fault which have had myself. The cause of this phenomenon is the final driver transistor, which drives the speedo motor, going into "thermal runaway" This is an intermittent fault which can happen from time to time, however there are a couple of clues worth watching out for.
The first is that when you switch on the ign, the speedo needle moves slightly, as if reading a couple of MPH, the other is with the ign on, if you watch the trips "tenth of a mile" drum over a period of time, it will move very slowly, ie. counting up.
This is due to a collector/emitter leak in the transistor. The transistor is a "BC337-25" available from Farnell Components, for about 50p for 5. I still have 4 left if anyone wants one
1990 GTA Atmo, 2003 Jaguar X type 2.5SE Auto, 2018 Kia Picanto GT-Line-S 1.25