Have fun answering this one...

[BabyDontYurtMe]

RIGHT. Its time to put this problem to the test, the Ford Transit Forum members.
My speedo on my Mk6 2.4l tdci has been broken for ages, and is still broken. Here are the details:

December - whole instrument cluster was borked, got it sent off to be refurbished, came back and all dials worked apart from speedo which works for only 2 miles then shuts down

March - take van in to autospark to have speedo looked at, he replaces speedo sensor and that does nothing. problem still persists. On start up, the speedo nearly always works for 500 yards, up to 5 miles. Then it shuts down and gives up. When not travelling, the speedo needle flickers slightly until it dies a death. It also reduces the vans power (slightly). However if I quickly turn off the engine and turn it back on (even fast enough so the engine doesnt shut down) the speedo lights back up and lasts another few miles.
We hooked an oscilliscope to the sensor cables leading to the speedo, and we are getting a digital signal even when the clutch is in. So somehow the sensor is sensing nothing and giving a reading to the speedometer, which is giving the ECU a hard time understanding wtf is going on. We reckon the reason the speedo is dying is because the ECU is panicing due to the constant speed reading despite having no revs/throttle etc.

Does anyone know why im getting the signal reading from the speed sensor even when the gearbox isnt turning? And would this cause the speedo to give up? Anyone got any ideas on what could be wrong? We have checked all wires to and from speedo/speed sensor, replaced speed sensor, refurbed instrument cluster. We are stumped.

Thanks in advance!

[Andy P]

1st thoughts are have you tried another set of clocks ?

[mitty]

December - whole instrument cluster was borked, got it sent off to be refurbished, came back and all dials worked apart from speedo which works for only 2 miles then shuts down


send it back to the refurbisher

[Punto443]

Check the alternator output, could be over charging and causing speedo to shut down etc

What year is the motor? Digital or analogue speedo?

[Timbo]

Going down a different route and assuming the Mk 6 gearbox speedo drive is similar to the Mk5.

Undo the propshaft from the gearbox flange and move it to one side. Check that the funny star shaped nut holding the flange onto the gearbox output shaft is good and tight. It clamps the drive gear to the shaft and if loose will not drive the speedo sensor.

This is a fairly common problem on Mk5's so worth a look.

Also try taking the sensor out of the gearbox and spinning the gear and see if the speedo reads (with ign. on).

HTH>

[BabyDontYurtMe]

Heyup guys, sorry for the delay in replying:

It is a 2006 mk6 transit with analogue clocks and a digital odo/trip.
Also a new development: Today he was sat there blipping the throttle and if he brought revs up to 3000rpm, he got a reading of 10mph on the speedo while the van was stationary. So there may be some crossing of wires somewhere or the ECU is mixing its messages. All things to consider!
They also drained the gearbox yesterday and got a borescope into the GB through the speed sensor hole to have a look around in there, and theres absolutely nothing they could see that could present a problem with giving a speed to the speed sensor.

We havent tried new clocks yet, but we can activate the speedometer and set it various speeds (send a speed signal from the ECU) using the laptop, so were about 99% sure its something wrong between the speed sensor and the ECU itself, rather than the clocks themselves. If the clocks were the bad bit, we wouldn't be able to send it various signals and whatnot from the laptop. or so you would think...

I told him about the possible overcharging thing, he said its very interesting and overcharging has caused some sorcery-like faults before, so hes going to check that next. Hes also going to rewire the signal cables, just incase some sort of contamination is happening between the signals. If its none of those 2, we are going to try new clocks/new ECU. We really are clutching at straws here!

[Punto443]

Later speedos get there signal from the abs rings and not a sensor

[BabyDontYurtMe]

Later speedos get there signal from the abs rings and not a sensor

Im not following you mate, ive replaced a speed sensor that is attached to my gearbox? Looks like a standard hall-effect sensor so could that be sensing something else?
What do you mean by later speedos? Mine has needles

[Punto443]

Speedos were changed around 2003, early ones have clockwork roll round mileage and a seperate clock mounted above the radio, later ones still have needles, but have a digital trip/odometer and another digital display for the clock under the Rev counter.

My 2004 fwd did not have a seperate speed sensor, it used the output from the abs to run the speedo, I suppose rwd could be different?

[BabyDontYurtMe]

Speedos were changed around 2003, early ones have clockwork roll round mileage and a seperate clock mounted above the radio, later ones still have needles, but have a digital trip/odometer and another digital display for the clock under the Rev counter.

My 2004 fwd did not have a seperate speed sensor, it used the output from the abs to run the speedo, I suppose rwd could be different?

Ahhh right, thanks. I wonder if it could be different, I cant work out what I could have changed in the GB if it wasnt a speed sensor? According to this workshop manual the TDCI RWD models only have this type of transmission -
http://workshop-manuals.com/ford/transit_2006.5_04.2006/mechanical_repairs/3_powertrain/308_manual_transmission-transaxle_clutch_and_transfer_case/308-03c_manual_transmission-transaxle_vehicles_with_mt82/description_and_operation/manual_transmission/

Van will be back with the sparky and his magic laptop on Monday to check the alternator thing. Fingers crossed huh!

[APH]

there is still an output shaft speed sensor, it feeds rotational speed to the engine ecu, however, that signal is not used to drive the speedo. As Punto says, the speedo is fed via can-bus from the engine ecu, via signals from the ABS control module. I would still be going with original thoughts / answers that the cluster is knackered, whether you sent it for repair or not. I`ve seen a lot that go for repair and come back the same or worse! have you actualy tried another set of clocks??

Andy

[BabyDontYurtMe]

Thanks for all the advice so far guys, ive dropped it with the sparky today and ive told him all the info you have given me. Suggested him to do everything he can to source another set of clocks to see if the speedo works in those, and then perhaps do an ABS check on all the wheels (sensors and harnesses) to see if theyre misreading or something. He said hes going to check the alternator charging too.

We will see how this week pans out... 3 weeks to go until we depart and I havent even done the full service yet so its getting a little tight!

[BabyDontYurtMe]

GUYS GUYS GUYS ITS FIXED!!!!!! ITS FLIPPING BLOODY WELL FIXED!!!!!

So, long story short: there was a contamination of signals between the vehicle speed sensor and the crank sensor (wires are in the same harness going up to ECU) so the speedo was getting some of the rev signals, which explains the "wavy" movement of the needle on the speedo. He put 2 fresh wires in from speedo up to ECU, and its absolutely dandy. Drove 20 miles today and the needle has been sat perfectly matching my SatNav speed readout.

Happy days! Unfortunately he couldn't tell if it would be something that was common in all Transits, since he couldnt actually find the piece of offending wire when he removed it - its just all his equipment stopped giving the weird signals and the speedo worked fine.

Mongolia in 3 weeks! Better get the oil changed!