weird speedo prob

[vincevtr]

Hiya, when I start my 2002 vtr from cold the speedo works fine for a while - about half-an-hour or so. Then it will die and not start again till the car's been left standing for a while... I've had to learn what speed I'm doing in each gear from the tacho with all the speed cameras. :geek:

Tried the obvious already - disconnected battery for an hour or so and looked at fuses. The only rational thing I can think of is that at a certain engine temp something isn't working - or shifting out of place? (Any better ideas?).

But what I really want to know is this: I've read in the Haynes that there's a speed sensor on the transmission somewhere and looking at the wiring diagrams it has a live, earth, and signal connected to it; the signal wire at some point splits into two and runs to both the ecu and the speedometer. Is it possible to reach the sensor and wires to check them visually and perhaps with a multimeter - ideally from above the engine bay?

Cheers

[FeArN]

i had a problem with loss of speedo and it was the plug off the sensor on the transmission, from what i remeber it was quite easy to get at but i had to remove the air filter, i have a vtr 2002, sure it was central and slighty down on the transmission the back, ill have a look at mine when i get a chance, could even take a pic. sounds like a wierd problem with urs but worth just checking the connection and wiring, u got a pic of the wiring diagram i can see?

[vincevtr]

Thanks - I appreciate that. With the crazy wind past few days I've not been out to poke around the engine, but now it's gone and if the rain stays off I'll have a look.

Wiring diagram was just that in back of Haynes - I cld scan it for you if you don't have it.

btw it's funny you live up in Wigan mate as it was driving back from there I first noticed problem! I'm at other end of the M58 - Maghull.

[FeArN]

yeah m8 dont have a haynes, ill take sum pics tomoz fri, not had the time with work, i travel down m58 most days, i work in burscough, im a electrian/auto but work on heavy plant

[vincevtr]

Wiring Diagram from Haynes:

http://img201.imagevenue.com/loc578/th_96355_Saxo_Wiring_122_578lo.jpg (http://img201.imagevenue.com/img.php?image=96355_Saxo_Wiring_122_578lo.jpg)

Also found this one and maybe more accurate (ecu MP7.2 - what the Haynes says is right for 2001 onwards vtr):

http://www.autoelectric.ru/auto/citroen/saxo/nfz/nfz.htm

[vincevtr]

Found what I think is speed sensor from what you say mate - cheers. It's directly below bracket that air-filter box fits in? Had a look yday and the plug connected to it with its three wires is on tight. Sprayed sensor with loads of electra-clean in the vain hope that'd fix things, but it hasn't.

Wondering if I should try replacing sensor - though it's a bit of a sod to get at because bracket is in the way as is upper gear linkage. Phoned Shitroen and a new sensor is about £25.

But as that's just a complete guess, would it be poss to tap into signal wire from sensor with a wire leading to an led? Then when speedo dies I could lift bonnet to see if led is still on or not (i.e. if it was then the sensor is fine and the problem lies elsewhere). Although I guess the led drain the current out of the circuit and stop the speedo working properly?

Moreover, if the sensor was faulty wouldn't that affect the ecu? The car runs very well - which is why I feel like I should put the effort into getting it fixed.... though this prob seems way beyond me.