406 Speedo Problem

EdwardRook · Post by **EdwardRook** » 04 Jan 2005, 22:37

I recently bought a 406 SRi Turbo which has a Sagem speedo.
The problem is that the speedo only works occasionally, twitching for around the first 10 minutes and then usually it starts to work normally.
Sometimes i can make it work by accelerating hard up to around 60 which seems to make it work.
Aparantly the previous owner changed the speedo interface box behind the glove box and since i've had it i tried putting in a different binnacle from a scrap yard but it made no difference.
i also had a mechanic try and check the connections on the gearbox sensor and i was told it was fine but i'm not too sure.
Any ideas would be appreciated greatly.
Thanks

wheeler · Post by **wheeler** » 05 Jan 2005, 00:14

whats a speedo interface box ?? my guess would be the (hall effect) road speed sensor in the gearbox,the proper way to check the road speed sensor is with an ociliscope,you should get good square wave pattern with a frequency that increases the faster you turn it.

zaki_406 · Post by **zaki_406** » 05 Jan 2005, 11:46

try the sensor located beneath the gearbox.