i have a skoda fabia 1 cluster .

i have the speedometer working but the rev counter not

Info about rpm will come by CAN messaging from engine ECU, I expect.

With VCDS  in section 17 (Instruments) the output tests should drive the needle to prove the instrument motor is ok 

Good thinking Nige.

yes i guess su it comes thru the can bus .

i dont have the ecu but i have the vcu that is after the ecu and plugs into the cluster at the output.

at the input there are no can bus wires

If you have the onboard supply control unit (vcu?) you should be able to talk to that with VCDS and do what Nige suggested.

To test the stepper motor that drives the rpm needle you could maybe swap the motors between speedo and tacho, I have a feeling they are the same.

the problem is that i dont know the rmp wire

i know its a wire because there is no other possible way for the ecu to send the signal thru the vcu

What year is the car? 

As I said, rpm data gets to cluster by CAN; VCU has CAN connections to every other module that uses CAN.

J285 is cluster.

the year is 2008

And i want to use the cluster with an arduino to show ingame rev ,speed,fuel,etc

OK, so a mk2 Fabia, but same applies. 

Don't think I can assist any further.

The RPM & coolant temperature are sent via the engine ECU on the CANbus drive network, the vehicle speed and fuel quantity are analogue inputs into the speedo unit however if the car has ABS then the vehicle speed is also via the CANbus via the ABS control unit 

ok thanks

1 hour ago, nige8021 said:

if the car has ABS then the vehicle speed is also via the CANbus via the ABS control unit 

 

Mine has ABS but the speedo signal still comes from a sensor on the gearbox. VAG like to confuse people.

Actually I might be wrong there. It looks like the gearbox sensor only does the odometer. Strange then, that I currently have the main fuse out of my ABS (because I haven't been arsed to fix a dodgy wheel sensor)  and the speedo still works.

 

Edited 11 June, 20223 yr by TMB

6 hours ago, TMB said:

Actually I might be wrong there. It looks like the gearbox sensor only does the odometer. Strange then, that I currently have the main fuse out of my ABS (because I haven't been arsed to fix a dodgy wheel sensor)  and the speedo still works

The strip fuse, or..?

I think there are two others, fuse 7 in engine bay and fuse 25 in cabin. Not sure what 'subdivison of labour' there is, but at a guess (based on the fault description 'return flow pump" that comes when strip fuse cracks, I reckon it might be as follows:

40A strip fuse - return flow pump power

30A blade fuse - all the 'brain' electronics and flow control solenoids

5A cabin (ignition only) fuse - probably just a 'wake up, he's going somewhere' signal.

 

In other words, parts of the ABS system may still be alive and working, except the ability to actually reduce the brake effort via the pump (the noticeable one).

Thanks, Pete. I have the 40A strip fuse removed and fuse 25 in the cabin (5A). If I don't take the cabin one out the ABS still malfunctions but with those two out it kills it and it just drives like a car with no ABS. I wonder what would happen with that 30A one removed. I won't bother tampering to find out, though

Edited 12 June, 20223 yr by TMB

Might have a play about on my Polo later, though it has no gearbox speed sensor.

1 hour ago, TMB said:

Thanks, Pete. I have the 40A strip fuse removed and fuse 25 in the cabin (5A). If I don't take the cabin one out the ABS still malfunctions but with those two out it kills it and it just drives like a car with no ABS. I wonder what would happen with that 30A one removed. I won't bother tampering to find out, though

 

Does disabling the ABS put the warning light on?

14 hours ago, TMB said:

 

Mine has ABS but the speedo signal still comes from a sensor on the gearbox. VAG like to confuse people.

On the MK1 it is the gearbox sensor according to the wiring diagrams but the OP has a 2008 MK2 and on that it's either the gearbox sensor or if fitted ABS 

Edited 12 June, 20223 yr by nige8021

12 hours ago, sepulchrave said:

 

Does disabling the ABS put the warning light on?

 

Bleeps on starting the engine, flashing brake warning light, steady MIL & yellow ABS light.

Edited 12 June, 20223 yr by TMB

8 minutes ago, TMB said:

 

Bleeps on starting the engine, flashing brake warning light, steady MIL & yellow ABS light.

 

Bugger, oh well, just have to keep driving round it...

Curiosity got the better of me and I pulled blade fuse 7 in the engine bay as well and took the car for a drive. Still the same three lights after clearing the codes but the red brake one now just stays on instead of flashing. Speedo still works normally.

Edited 13 June, 20223 yr by TMB

16 hours ago, Pete_Ex-Wino said:

30A blade fuse - all the 'brain' electronics and flow control solenoids

 

It's actually 25 amp, Pete.