Hiya my 09 Rev Mondeo battery warning came on so I took it to the garage and they have just got back to me saying that the cable ties around the wiring loom on the alternator has eroded and water has got onto it and damaged the ecu.

Is the possible as no previous warning lights shown and would a dodgy ecu affect the fuel economy

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Firstly, you'll probably get better information if you say what engine your car has. In particular, without a clue as to whether it is a Petrol or a Diesel makes things unnecessarily hard.

Hiya my 09 Rev Mondeo battery warning came on so I took it to the garage and they have just got back to me saying that the cable ties around the wiring loom on the alternator has eroded and water has got onto it and damaged the ecu.
Is the possible as no previous warning lights shown and would a dodgy ecu affect the fuel economy

It sounds a bit implausible. I could see the water ingress causing damage to either the alternator or the battery, but it certainly shouldn't damage the ECU (I'm not quite saying that it is totally impossible, but I'd go for very unlikely, and it is really the kind of thing that Ford would have tried to ensure does not happen).

If it were as described, the problem of water would have been getting worse over a period of time, so I'd probably expect to see a gradual worsening, rather than a sudden fault (eg, the fuel economy, if you are saying that has got worse - I'm not clear what you are actually say happened to fuel economy, if, indeed, anything has). Which happened?

If the ECU is 'dodgy' that could affect fuel economy, but I'd think that there is more chance of some corrosion getting between a couple of wires and that being the problem rather than the ECU itself. Depending on which wires, almost anything could happen, but really damage to a module shouldn't be the outcome (shouldn't!).

Did the garage say that the battery, the alternator and charging were ok?

Its 2.0 140 bhp diesel sorry I missed that off the fuel economy has bein really poor on it am averaging about 35mpg on a 70 mile trip and it has been poor from day 1 I just assumed that might be a reason behind it as no warning has been or any other prior indicator

This is what warning came on

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