306 tacho

bad driver · Post by **bad driver** » 28 May 2004, 22:09

Hi there, My speedo recently failed so I decided to scour the scrappies to find a suitable replacement. Anyway, I struggled to find a good match due to there being so many. Anyway I managed to find one that was cable driven the same as mine but it has a tacho where my old ones had a clock. I know there is a sensor on the flywheel which I believe picks up on the TDC hole. However the tacho doesnt work, I know there is 5 different positions for multiplugs on the back of the clocks. My car only has 4 multiplugs so I'm assuming its the missing multiplug that is the problem? can anyone with a tacho confirm that there is a 5th plug (blue one I believe) which would fit top right as you look at the clocks face on? Or is it possibly a missing relay somewhere? I know all the fuses are right as its on the same fuse as other things according to the manual.
Also any idea how hard it would be to get this working as it would be nice to have.
It also has an oil pressure or temperature dial on the same face as the tacho, this lights up and moves slightly when ignition is on but the goes off once the engine is running. Does this sound as though it may be working? where would the sensor be for this?

batwad · Post by **batwad** » 02 Jun 2004, 13:37

Fortunately, it's a while since I removed my instrument panel [:)] so I can't confirm whether there's four or five multiplugs. I've got a spare IP in the garage though, so I'll have a look one evening this week at the back of it to see how many connectors there are. There won't be a missing relay since it's not a high current circuit.
It shouldn't be too hard to get it working; I imagine all the wiring's in place, maybe even the TDC sensor. You might have been unlucky and picked up an IP with a duff speedo [:(] Another thing to bear in mind is the redline point on the speedo. If it's 5000 then it's a from a diesel, the petrols redline higher. I hope you got the right one!
From your description of the oil gauge, it sounds like oil level. What are the markings on the scale? Oil level simply reads "mini" to "maxi" as I recall. It should illuminate and the needle move up the scale with the ignition on, and reset to mini with the engine running. I think the sensor is fitted to the back of the sump, but Haynes can confirm this.

solara · Post by **solara** » 02 Jun 2004, 14:15

If you do neet to run your own wires, all you need to do is run a pair of wires from the sensor direct to the connector on the back of the tacho. The circuit diagram is in the Haynes manual.
Sorry cant remember how many connectors on the back of the dash. But I do recall it its the connector just above the tacho display which carries the tacho signal (blue seems to ring a bell).
PS diesel and petrol tdc sensors are likely to be different, so make sure you match the right pair (tdc sensor + dash).

solara · Post by **solara** » 02 Jun 2004, 14:18

PS your car probably already has the TDC sensor fitted, as this is used by the garages to tune the engine. It is somewhere on the left hand side of the fuel filter, with a 3 pin connector of which only 2 are used.

bad driver · Post by **bad driver** » 02 Jun 2004, 21:20

Hi, thanks for the replies, I was begining to give up on anyone anywhere knowing. Anyway, having checked the Ip is from a petrol as redline is at 7k, but even if I get it working and it never redlines I will be happy. The TDC sensor is in the back of the engine, pushing against the flywheel from what I have found out. I am wondering if maybe mines not working??
Having checked the wire tracks on the back of the IP all wires from the tacho seem to go back to the yellow plug which I have so all is well at that end. I also seem to have a fuses in places as well so no worries there.
Could it be the tdc sensor is incorrect for the tacho? or possibly the tdc sensor doesnt work?

CITMAN · Post by **CITMAN** » 03 Jun 2004, 00:48

if its from a petrol i doubt you will ever get it working as with a petrol i believe its driven off the ignition system where as on some diesels its driven off the alternator.

batwad · Post by **batwad** » 03 Jun 2004, 13:29

Even if you get it to work Richard, there's no guarantee that the scale will be correct since it's for a completely different engine. It would look nice, with a needle flying all over the show, but not telling you much of any use.

solara · Post by **solara** » 03 Jun 2004, 14:24

The TDC sensor is an inductive pickup sensor, so unless you have an oscilloscope you cant test it properly.
As a rough test...You can measure the resistance of the TDC sensor from the IP and plug connecxtor using a multimeter. If you get a reading (less than 4k if I remember right), then disconnect the TDC multiplug in the engine bay, and you should get infinite resitance.
This will atleast test the wiring.
Pug TDC sensors are prone to failure with time, mines went after 8 years.
I dont expect mixing tdc_sensor+ip dash for petrol/diesel will work. I have a 306XTDT and was told a TDC sensor from a xantia 1.9td would work, but it never did. In the end bought an original tdc sensor from a dealer (twice the price but atleast it works!).

bad driver · Post by **bad driver** » 04 Jun 2004, 15:07

OK, think I may give up with getting it working again then!! Might put the clock back in instead!!
Oh and Batwad, why do you never post on the other site???

batwad · Post by **batwad** » 04 Jun 2004, 16:22

Other site? Is that The Dark Site? Is the force strong in that one?

bad driver · Post by **bad driver** » 04 Jun 2004, 23:17

no the PGAC !! although it may be the dark side but as it lured me in I have no idea which side is right anymore!!