406 speedometer

why the speedometer on a406 desel 2000 keep stoping now and again

 

Faulty gearbox sensor and/or the wiring to it. A specialist can fit a second
hand one for around £20 or 30 euros.

 

I’m getting a similar problem.

My speedo works for the 30 mile journey into work. Whether it works on
the way home is down to luck. Sometimes it will flicker back into life
for a couple of seconds, sometimes it will work for the rest of the
journey.

I’ve got a speed camera unit in my car which works by GPS. That’s
putting my speed about 5-7 mph lower than the car is reporting
(measured at a constant speed). Is that normal or is it helping to
point in the right location? One thing that might either help or throw
you off track - very occasionally the rev counter will flicker - I’d
say it’s only happened about 3 times in 2 months though.

I’ve been getting conflicting advice, some say it’s the transducer
behind the gearbox, some say it’s the sender unit.

I gave the contacts of what I thought was the sender unit a good
clean, but I think now it might have been the reverse light switch I
cleaned. At least that won’t let me down now! Whereabouts should I be
looking?

Any ideas as to what might actually be the culprit as to the speedo
problems I’m describing? Or am I looking at changing both units? I’m
quite handy with a set of tools, I’m of the standard that has no
problem changing brake discs, alternator etc - I’ve even tackled a
camshaft replacement before with no problem.

 

You have the gearbox unit which is where the O/S driveshaft goes in to
the box. Held in with a 6mm allen key bolt. Be prepared for a slight
loss of oil when removed. And then there is the control unit which is
behind the glovebox, accessible when you put your head in the footwell
and peer upward. There are 2 or 3 different units up there, so I
suggest you purchase the parts first so you know which control unit to
change!!