tacho/rev gauage not working

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dava4x4

Member
Joined
Feb 17, 2015
Messages
22
Evening chaps, new to the forum, recently bought a 2001 2.7tdi t2 auto and loving it, the only problem iv got is the tacho is not working atall, every other gauge on instrument cluster working as it should, i have the workshop manual and i see there is a self diagnosis sequence for tacho etc ... problem there it states to hold in the 2 reset buttons? Well on my clocks it only has one :/ ...... my names Dave btw :D cheers
 
You've got no rev counter?

Welcome btw, great club here, you'll enjoy, in the mean time got any pics of the motor :nenau :thumbs
 
Evening chaps, new to the forum, recently bought a 2001 2.7tdi t2 auto and loving it, the only problem iv got is the tacho is not working atall, every other gauge on instrument cluster working as it should, i have the workshop manual and i see there is a self diagnosis sequence for tacho etc ... problem there it states to hold in the 2 reset buttons? Well on my clocks it only has one :/ ...... my names Dave btw :D cheers

Glad you've posted this as I've been looking around for an answer for this for James
 
Morning... iv got a rev counter but it doesnt work :/ il post some pics of my beast soon :)
 
Welcome Dave,
The Tdi's are fully electronic, and take a signal off a sensor on the engine, this goes through the ECU.
I'm not sure where the sensor is as my Td is different. It could be the Crank Position Sensor? not sure.
However the Tdi instrument clusters are well known for intermittent faults , mostly caused by dry solder joints, or solder joints that have cracked and become open circuit over time and with vibration etc. Or poor connections.

One or two other members have had similar issues and have fixed them in a few minutes, once the cluster is removed.
It may be worth a quick search, no doubt someone will be along with some thoughts or links to past posts soon... It might even be me later lol...

Best regards,
Rustic
 
Nice one rustic :) i guess il start with removing the instrument cluster see how it looks behind there, im away this weekend in the caravan, looking forward to hitching up and towing with this beast, hopefully all goes well, never towed with an auto before so should be interesting :D
 
The early td has a sender tapped into the front timing cover blow the powersteer pump and is a two wire sender

The later eti engine sources its signal from a similar two wire sender screwed into the side of the injector pump...

The eti signal is sent to the ecu converted into a sqaure wave signal then sent to tacho where as the earlier td is an analogue pulse direct... hence the two types are incompatible,..
 
from memory the signal is converted into a positive where as the earlier was a negative pulse,

so if all else fails you can take a pick up off the alternator and calculate the pulley ratio between the crank and the alternator and insert inline a suitable resistor to correct the signal strength to the tacho.

some fault's i have seen are corroded wires as they exit the sender unit on the side of the pump..
DSCF3294_zpse959175c.jpg


it is the plug next to the blue tag.

next is the black 8 pin plug that sits front right on the intake manifold where the loom from the injector pump plugs into the main engine harness...

check the wires and disconnect the plug and check for corrosion on the pins.

following that the next option is to remove the instrument panel and check for breakages in the copper foils that travel from the plugs to there respective instruments and lights.

next give the signal wire from the plug to the tacho signal wire a jump from a power source, the tacho needle should swing right around to red line.
if it does the tacho is working correctly. if it does not, it is more then likely had it....
 
yours is the later type so recon solder joints are bad, you can either redo each and every one or with a magnifying glass check for minute crack around the pins and solder, Rick
 
yours is the later type so recon solder joints are bad, you can either redo each and every one or with a magnifying glass check for minute crack around the pins and solder, Rick

Rick - I have just got a head worn magnifier/led as I can't see the joints well enough to solder. Do you mean every joint behind the LCD display or every joint on the board?

Steve
 
Rick - I have just got a head worn magnifier/led as I can't see the joints well enough to solder. Do you mean every joint behind the LCD display or every joint on the board?

Steve

You can normally see a poor solder joint, it will look like a small dark circle around the component or connector leg, where the solder joins it.
Sometimes the solder looks a matt colour, instead of shiny.
Sometimes using a small terminal screwdriver on the component legs can be enough to see the leg move.

If you do solder all the joints as a precaution, check for small solder whisks that can short out two pins.

Make sure you use resin cored solder, ie with flux already in the solder.
If you have a solder sucker, that will be handy for removing any excess solder or accidental links on the board.
I could never use desolder braid with any success, as often it lifted PCB tracks due to overheating.

Do not apply too much heat, for too long on any one connection, as it can damage the component, and also lift the thin copper pcb tracks.

My first career was in electronics, so some tasks are second nature, so final advice... don't rush it, take your time be systematic, ie choose one area at a time to solder so you don't miss any.

General... for any other PCB repairs.
As with any rework of any PCB, make sure there is no power on the board.

Rustic
 
excellent write up Rustic as always, Rick

I don't mind sharing and spending some time writing when this is my area of expertise.:thumb2
After all, most members do this and more to help others.:thumb2

I just want to keep these trucks on the road, who knows, in another 20 years I might be needing some parts to keep mine running...:augie
:lol:lol:lol
 

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