Speedo problems

[Ben5732]

Evening. a friend recommended I come here for a problem with the other halves car, it's a 406 but said you guys were helpful so here I am
Car is a 406 2.1td, notorious for it's Speedo problems, I believe it's a xud unit if that helps. Speedo was flicking up and down constantly sometimes I would read correctly other times it would stick just shy of 40. I've taken the unit appart and found the solder was shot, resoldered it all now the Speedo doesn't flick around anymore, however it's caused another problem. the Speedo once the engine is turned on flicks straight to 40mph when stopped then rises like normal but 40mph to high constantly any idea what it could be or what I've broken whilst doing it? just as a side note it is not the sensor in the gearbox or the box thing in the passenger footwell. cheers

[Niall]

Welcome!
Its difficult to say without knowing the setup in a 406 but assuming its similar to a 306 (peugeot wiring is normally pretty much identical over models of the same year), it will either be a bad sensor or dials and i would put my money on the sensor which i know is he same as the 306 ones which are notorious for dropping in/out or just not working all together.
If i was you, get a new sensor. I would phone peugeot as i know the 306 ones really aren't that expensive from them!

[Ben5732]

can 100% say it ain't the sensor definitely clock related, apart from when the solder on the back was dry causing the original issue it did read the speed perfectly it's only since resoldering it's showing the incorrect speed.

[andywhy]

As per our conversation on FB (yep I introduced him here!), you say the needle came off when you were working on it so it will have gone out of calibration. What you'll need to do is take the needle off when it's pointed at 40mph (engine running), then put it back on to point at 0mph (engine running) or on the stopper (engine off). That should do it.

[Niall]

Ah you never said you had been fiddling with the dials!
The dials should self calibrate when the power is applied to them and also occasionally when the car is switched off. If i was you, unplug the dials, push the needle down to about 10mph then plug them back in and with any luck they will jump down to 0...may go well past 0 in which case, unplug, move back up to around about resting point and plug in again. May have to try this a few times before it gets it right.

[Ben5732]

shall give that a go tomorrow will post with the results cheers gents.

[Ben5732]

update on the situation, gave this a go however now my mileage aint showing at all (bulb is working) and not one of the clocks in the car is working fuel or heat either, checked all fuses and all are ok

[andywhy]

Connector possibly not on properly? Or the solder job was worse than you first thought? I'd say unplug it all and plug in again to see if that helps.

[Ben5732]

Also appears the power steering is heavier than normal now since thr clocks do not work at all. soldering wouldn't explain why the clocks do not work what so ever unless it's gone in multiple locations :/

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had.a bit of a Google may well now be the Speedo control box has gone aswell :/ would explain powersteering being heavy it appears. any idea where to get one? thanks

[Martin306]

Get another set of clocks to try.

seriously

[Ben5732]

Can't find any anywhere loads of hdi ones but non for my model

[HDi--Power]

The left hand side plug controls the mileage/temp etc so id be looking at that connection. Also if the speedo etc has little needle stops close to zero it is NOT self calibrating, if it doesn't then it is

[Ben5732]

Nothing is working on clocks currently or the speed sensitive powersteering guess next course of action would be to check the plug things with a multimeter? :/ think I may of fried the Speedo interface unit :/.

[HDi--Power]

It looks like your soldering job may have killed the instrument cluster sadly