Defender TDCi Speedo

[aesmith]

So a three years ago the speedo failed, I replaced the transducer with a cheap aftermarket part and all was good (aside from some hassles fitting). Just recently it started working intermittently, sometimes stopping during a journey and sometimes starting again.

I wasn't convinced it was the transducer but I swapped it anyway, that seems to have fixed the intermittent fault but the speedo read unreasonably high. Something near to 50% fast. So that was returned as faulty and I bought another one, this one claimed to be genuine LR. Same issue, reading 70 mph when probably not even hitting 50 (1,500 rpm)

So the question is whether there could be something other than a definitive transducer causing this?

And a second question, assuming it is the transducer, what's the advice on parts? Are any of the branded aftermarket parts worth trying, or genuine VDO not in an LR packet. Or does it have to be from LR.

 

[sako243]

There are multiple gears inside the LT230 transfer case that are also used to set gearing for the speedo.

So you've got varying transfer box ratios (I think the Tdci went to 1.2 box by default), then you have different gears on the speedo drive and possibly also various settings on the speedo itself (I think the speedo attaches to the transducer and then there's an output from that to the ECU).

 

[aesmith]

Cheers. I've not changed any of that, the overall gearing and speedo drive gearing is the same as it's always been. One thing I note is that the same part number is specified for both the TD5 and the TDCI, although I'm sure the TD5 had lower gearing.

 

[m_c]

I changed one of these years ago and seem to remember that there were various sender options, and you had to make sure you got the correct one.

 

[aesmith]

I only see one option, part code YBE100530 listed as suitable for all TD5 and Puma (TDCI) Defenders. That's the code on part I fitted three years ago, that was correct. And also the code on the packaging of this new and presumably incorrect part.

Which leads me back to, could there be anything other than an incompatible sensor causing this?

Changing is a bit fiddly but I'm tempted to swap back to the intermittently faulty part, just to confirm it gives the correct speed. Assuming it works of course.

 

[Turbo]

Does it need to be calibrated to the vehicle using a computer?

 

[sako243]

Does it need to be calibrated to the vehicle using a computer?

Nope

 

[aesmith]

Well not remotely sorted. Seller of the first over-reading sensor refunded. Seller of the second one sent a replacement, but I couldn't get that to work at all. Looks like l damaged it when fitting (trying to fit). So I don't know if that would have read correctly or not. Those are both branded VDO made in Germany with some part numbers as the one I removed.

The only progress was refitting the old intermittently faulty unit and confirming it reads correctly. So the over-reading does look like a sensor issue, not vehicle.

 

[julianf]

If you have a scope, you could probably spin the sender at a stable rpm, and scope the pulses.

I mean, obviously, if the new one isnt working with the speedo, you know that anyway, but, when you get a replacement, you can then quickly check before messing about on the vehical.

You will also be able to see if the pulses are "nice" or all over the place.

 

[julianf]

Nope

Is there no way on the latter builds to adjust for tyre size etc? On the old ones you got all the different coloured gears on the senders, but the electronic ones dont have the option at the sender end, so i assumed it was done on the gauge end, like the VDO units. You say it isnt, but how else can you calibrate them at all? Maybe you dont, i guess?

 

[aesmith]

I guess there must be some way, but this is a huge difference, as if it thinks the wheels are four feet in diameter. Also there's the fact that popping the old one back gave correct reading.

Without a scope I was wondering about spinning it with cordless drill while connected to the wiring. See what the speedo reads. I suspect the drill might be too fast, just twirling it between my fingertips gives a reading.

 

[sako243]

There is a setting I think in the EEPROM in the unit that does pulses per mile I think but by and large they just didn't care because there wasn't much of a difference.

Have a read through the thread Dave and so on put on LR4x4 - I can't remember the details if there is or not.

 

[aesmith]

From a quick rummage around the coloured gears are internal to the transfer box, for example ...

Whereas what I'm replacing is the external transducer that it drives. There seems to be only one type listed part YBE100530. And I have examples marked with that part number that over-read wildly, and one with that same part number which reads correctly.

 

[julianf]

I think there is some oddity, that only one gear works with the electronic one. Iirc the one that works with the electronic sender has a smaller hole in the top of it and if you change the gear to one of the other ones, your electronic sender's "male" part would just rattle around in it and not engage properly.

...so you can't change the gear (assuming I'm right and there's only one for the electronic one - I think it's a green wheel one?)

 

[julianf]

Is there any possibility that someone, in the past, has bodged it by packing out the large hole in one of the other gears to make it work with the electronic sender, and that packing has now come out?

Would happen if someone had swapped the transfer box in the past and couldn't be bothered to swap over the gears.

 

[aesmith]

Is there any possibility that someone, in the past, has bodged it by packing out the large hole in one of the other gears to make it work with the electronic sender, and that packing has now come out?

Would happen if someone had swapped the transfer box in the past and couldn't be bothered to swap over the gears.

I don't see that either of these scenarios would make it read differently just by changing the external transducer. Surely the "packing fell out" example would mean it doesn't work at all, how would that make it over read?

 

[julianf]

I don't see that either of these scenarios would make it read differently just by changing the external transducer. Surely the "packing fell out" example would mean it doesn't work at all, how would that make it over read?

Sure, it wouldn't make it over speed, but it may make your original unstable or even one not read at all.

Its just a possibility. It's not like I'll be betting money on it or anything.

 

[julianf]

I'm remembering more of this now, so just for background info -

I killed the transfer box in my 300tdi defender.
I had a 300tdi disco box spare, so fitted that.

And then realized that the cable on my defender would not fit into the disco gear end.

I couldn't get one of the gears out to change them over...

...so I attempted to file down the end of the cable to make it fit. But it's some wound thing, so that didn't work at all.

In the end I was patient and kept dosing the housing with penetrating fluid for a week, and then it came out fine.

There is a website somewhere that had photos and tooth count on all the gears, but, as I say, I think there is only one single option for the electronic sender. I guess as it's "calibrated" elsewhere, but, as discussed prior, this may not be an easily accessible user option.

At some point I plan to replace the mechanical system on the defender for the electronic one again and get a vdo speedo. These have to be calibrated by the user on fitment.

 

[Smallfry]

Are you sure the old one is reading correctly, but double checking the speed reading against a satnav or phone ?

On my Vauxhall and Renault vans, you can access the ECU to set the tyre size, maybe LR have the same ?

 

[aesmith]

Are you sure the old one is reading correctly, but double checking the speed reading against a satnav or phone ?

I've only done a rough sanity check. But for the over reading units it's blatantly obvious, reading over 70 mph at 1,500 rpm for example.