I'm still having major problems with my 2004 Multijet Dualogic. It refuses certain gear changes, though an end-of-line service via the examiner always sorts it out again for a while.

I think it's electrical because cleaning up a bad earth on the rear light cluster sorted the problem really well - for a while. Then when it failed again and I turned the ignition off, my ignition-only radio remained on. I wish I had thought to test other electrical things coming off the fusebox at the time. But I removed the radio from the car to eliminate it.

My mechanic thinks it's mechanical. He's replaced the clutch because the examiner finally began giving errors and they were all about the clutch. He did some reconditioning on the gearbox but I don't know exactly what. The problem remains. Now he wants to try a second-hand gearbox. I'm doubtful.

If we go the gearbox route, I don't know what part I'm after. I'm getting very conflicting information about the gearbox. How can I know for sure if the diesel Dualogic gearbox is the same as the manual gearbox when even Fiat people are contradicting each other?

Electrically its likely to be the same as petrol though the gear shift ECU map will be different. I would rule out electrical before changing the gearbox.

Check all electrical connections and earths associated with rear lights and the reversing switch on the gear shifter. It may be worth running additional earth leads from the rear cluster to new self tapper screws.

Also make sure all engine bay earths are 100% and of course the battery itself and alternator charging circuit.