Speedo stopped working

[220bhp]

I have just put my car back on the road and the speedo wont work.It was fine before.
I did not take the gearbox out for the rebuild just the engine,which makes me think its electrical.
I replaced the bonnet cable,and to do this I had to drop the shelf under the steering wheel and could of disterbed somthing.I dont think its conected but the oil presssure gauge gos right round when you turn on the ignition.
Any advise would be much appreciated.

[Pirvu Eugen]

About the oil pressure...check the wires at the pressure sensors...maibe you fitted them wrong.
About the speedo...check the plug at the speed sensor at the gearbox...use some contact spray.
Hope will help!
Regards!

[220bhp]

I will check

[LSG]

My speedo stopped working as i was driving.I removed the panel under the clocks, so i was able to get my hand up to the back of the speedo and when i pushed the wireing it started working again. Happy days nice and easy We like that sort of repair Good luck. I hope yours is nice and simple to.

[4WheelDrifter]

As always my first question is, does the odometer still work?

[220bhp]

Stu, the odometer is not working.

[porkkis]

Have you installed a new radio?

[220bhp]

No new radio but,I did fit a new bonnet cable and leaver.is it possible I could have disturbed something.

[Tony Stark]

Im pretty sure that on mine the speedo needle jumps very slightly when i turn the ignition on, which lets me know the instruments are behaving and its gunna work for me when i start driving. Think i have a dodgy cluster connector issue as bumps affect it sometimes.

[4WheelDrifter]

Stu, the odometer is not working.

Any fault codes? Like 1231?

[220bhp]

Pulled the codes with vagcom,and got the following.

00533

00532

05133

01262 n75 was unpluged

[4WheelDrifter]

Check your earths.

Also check that the instrument cluster is getting a signal from the sensor.
Put a multimeter between pins 20 and 21 on the 26 pin blue connector at the back of the cluster, jack the front left wheel off of the ground and spin it.
If that's ok then it's most likely a cluster problem. A faulty speed sensor usually throws a code.

I'm assuming you would spot something obvious, like the old peeling gauge making the needle stick.

[AndyP]

Check your earths.

Also check that the instrument cluster is getting a signal from the sensor.
Put a multimeter between pins 20 and 21 on the 26 pin blue connector at the back of the cluster, jack the front left wheel off of the ground and spin it.
If that's ok then it's most likely a cluster problem. A faulty speed sensor usually throws a code.

I'm assuming you would spot something obvious, like the old peeling gauge making the needle stick.

I take it I'm looking for a change of resistance across pins 20 & 21 when the wheel is turned? I have nothing, but the needle does jump a little when I switch the ignition on.

[johne]

T26 pin 20 is the one to concentrate on, pin 21 is just ground.

If you've disconnected T26 from the back of the instrument panel and you're connected to pin 20 and ground on the T26 loom side then you are looking for a change in resistance between zero and infinate - the speed sensor in the gearbox is just a reed switch being connected to ground by a magnet rotated by the gearbox output.

Better, if you can, is leave the T26 connector connected to the instrument panel but at the same time connect a voltmeter to pin 20 and ground. With the ignition on and turning a wheel you should see a voltage then nothing, then a voltage again as the reed switch in the gearbox holds pin 20 to ground.

I cured my intermittant working of the speedo recently by taking the instrument cluster apart and cleaning the pins that the speedo unit slides onto on the instrument panel PCB to make contact but obviously there are several connections between the speedo unit and the gearbox sensor and any break in yours may not be in the same place.

The gearbox speed sensor cannot of it's own "throw a code" as it has no connection to the ECU. The speed signal, VSS, is output from the dashboard speedo and is sent to the ECU (pin 50) but I have no idea if the ECU logs a code if it's missing and either the speed sensor, speedo unit or wiring could have failed to make VSS disappear.

John

[AndyP]

Thanks, I'll try that tomorrow