speedo cable dodgy doin our heads in pls help

[robbiel900]

hi we have a 2002 1.9 fiat ducato (swift mondail) campervan our speedo started playing up a few months back so we took it to our local quickfit garage and they suggested a new cable so we went ahead and had the work done with no joy it works for days on end and will then start playing up again so i take the speedo assembly out and fiddle with the cable at the back and it works again for a few more miles or afew more days but with me fiddling with it, it could be wobbling the gear box end i was just wandering whether someone has had the same problem or know of the problem and could suggest what to do next thanks best regards

 

[varesecrazy]

What is the actual fault ?,
does it SWAY either side of the true speed..??,
that's a DRY or badly routed cable,


or does it not actually give a reading.?
that could be a fault in the gearbox / or the speedo head,
any other connection issues should have been spotted by the person changing the cable..!!

Charlie

 

[robbiel900]

First of all thanks for replying so quick. It just gives no reading at all i know they should of but the nxt thing they want to do is take the gearbox off and take it apart to see what the fault is and thats gonna cost a bomb im a nearlly fully qualified machanic so dont mind getting my hands dirty i just have no clue at what to do nxt as ive had no experience is there any tests i can do to on either end to see what ends at fault thanks again

 

[fingers99]

Could be the drive head in the gearbox. Remove it, take a peek.

But first I'd check the gearbox oil level, maybe drain it and check for swarf.

Is the diff noisy?

Non functioning speedos (generally driven by the differential) can indicate a gearbox which is about to die.

Main problem with rebuilding gearboxes is finding parts and documentation.

 

[robbiel900]

hi we're convinced its the speedo end we have no noise from the diff gear changes are smooth the clutch is a little heavy but i dont know whether thats relevant it seems that if we fiddle with the back of the speedo it works again i hate mysteries errghhh :bang:

 

[s130]

Does the distance counter in the speedo work? or do both the speed reading and distance both fail together?

 

[portland_bill]

Take a logical approach.
If the cable is new, it should not have any issues with drive going in at one end coming out at the other.
Now we need to know whether the gearbox is driving it. As said above, does the mileage still increase with the speed not reading? If it does, the fault is inside the speedo and this needs rebuilding.
If both speed and miles are not responding, fault may be cable not turning, or still a fault in the speedo.
Can you disconnect the cable from the speedo and watch it turning or not as you drive? This may help determine if the fault is at the speedo or at the gearbox.
Disconnect the cable from the gearbox end, now you need a means to turn the cable, but it goes anti-clockwise, so a reversible drill on a low speed, or an electric screwdriver with a chuck, or a hand drill, or something similar. Turn the cable with the top end still attached to the speedo and see if it reads. If it does, fault is on the gearbox drive, if it does not turn, the speedo is at fault.
The gearbox drives the speedo, usually with a gear around the diff, which rarely gives trouble onto a pinion that drives the cable. This is usually a nylon gear shrunk onto the shaft that engages with the cable. These pinions can release their grip, allowing them to turn on the shaft. This is the most likely cause of your problem. Remove the pinion from the gearbox, probably one bolt and inspect the pinion and shaft. Sometimes the pinion teeth just wear out.

I've tried to look at ePER, see link on top of this site, but not knowing exact vehicle this is difficult. Speedo cable seems to be with instruments, but all those I've looked at seem to be driven electrically, so I can't find the speedo pinion. Can anyone point us at the correct section?