Hi, for the past 3 weeks or so the dual fans are constantly running on my octavia 1.9tdi. They come on with ignitian (even during the bitterly cold weather we have just had in the UK) and run for about 5 or 10 seconds after switching off. It is taking the engine a long time to reach temperature and puts an extra load on the battery in cold mornings.

My mechanic thought it was a sensor switch but this made no difference, an auto electrician had it for a day and couldn't diagnose it. A friend of mine plugged his Vagcom in and had a Powertrain Bus. Instrument cluster fault, which my local Skoda dealer said was a fuse box under the scuttle panel that was probably corroded. I removed the scuttle panel but there was no fuse box there, I think it was the ECU and there were no signs of corrosion although I couldn't remove it altogether. Would this be the component at fault? I was set to book it in at my Skoda dealer but someone told me it could cost about £1200 for ECU replacement!

Does anybody know what it could be and if it is the ECU how much replacement is likely to cost?

Is this the 57 plate car referred to in your previous post?, I've moved it to the Octavia 2 section.

I've seen fans run constantly to the point of completely draining the battery on these, both times it has been down to water in the fusebox which is in the engine bay on the passenger side. Ideally the fusebox needs to come out, be dismantled and dried out.

The cost for ECU replacement from a dealer using new genuine parts seems about right to me.

It looks like I have finally got this sorted. It took a lot of investigation by various people and I was warned by my local dealer that it was looking like a problem with the ECU interface that would cost £1890. It turned out to be a faulty master fan with integrated control that was replaced (costing just under £500 with labour) and all seems ok now.

I was advised that the scuttle panel was a poor fit although nobody else who looked at the car has advised this, could this be a cause of electrical component failure and should I consider eplacing it?