speedo sensor

[DAF4TRUCKS]

Speedo fluctuates wildly after driving 25 miles or thereabouts.Have adjusted the gap to 8 thou as recommended in the 'bible'.I'm thinking .. the sensor is located quite close to the exhaust is this the reason why it is OK from cold or is the sensor just faulty.Another confusing thought.. after madly fluctuating it goes back to zero whatever speed you are doing,should not the ECU send messages which would cause tickover issues? Aplogies for going on a bit but does this ring any bells, or is it just a new sensor which is required.

Cheers all.

[Cider Andy]

It might be the speedo itself. I don't know how you eliminate either, unless you borrowed them. Do a search on this forum, there's quite a few speedo problems reported with some good advice to fix them.

Sorry I couldn't be of more help.

[paulathome]

Had a similar problem on my chim.
2 weeks after I bought her the speedo would work but only when doing more than 30 mph.
Then it would only work at more than 30 mph but jumped all over the place.
Then stopped all together. Replaced sensor (cost about 40 quid) and everything has been fine since.
Cheers
Paul.

[the dodger]

Similar story only with mine it was reading way too low. Then started flickering and getting very lazy. I had a new toothed wheel fitted (with more teeth!) and a new transponder. It came with all new connectors etc and is now rock steady - and quite accurate. Meanwhile my tacho is jumping about all over the place!

[Cider Andy]

the dodger said:

Meanwhile my tacho is jumping about all over the place!

Have you fitted new plug leads? Try rerouting the HT leads away from the LT coil connections and wiring. This is usually caused by the rev counter signal wire (driven by the coil) picking up spurious interference from one of the HT leads.

[DAF4TRUCKS]

Thanks for the replies, I will proceed by the process of elimination, bit like England really.

[TVRtoe]

Had similar irratic response, bouncing all over the place. Sensor change didn't cure it, but found securing nut on speedo teminal had come off and crimp was hanging on loosly. A new nut cured the problem.