Serious electrical problem Ford KA

[shero101]

My son has a 2001 Ford KA (60k miles) that has developed an intermittent problem. Sometimes when driving if he puts the fan (blowers) or the wipers on then the engine cuts out completely (the headlights go out as well). It won't restart unless the wipers and/or fan is in the off position. In addition to this, when the engine cuts out all the lights on the dashboard light up including indicators and high beam lamp even though they are'nt on. As you can appreciate this is potentially an accident waiting to happen if the problem happens when driving at night in the rain. It has been checked by an auto electrician and a main Ford dealer. They both said it passed all diagnostics and there is nothing wrong. It has been family owned from new, never messed about with the wiring, serviced regularly. It is clearly not a known problem. Any ideas please ?

[Tuvok]

I did a quick search for ford ka problems.

One site I found had a chat box supposedly to speak to a ford mechanic - might be useful, might not!

http://www.carcomplaints.com/Ford/KA/

[Hymie]

I would totally agree with Methyl – it is almost certainly an earth (or return) path fault.

The reason it happens when the blower or wipers are switched on is that these draw a high current and the voltage at the circuit location where these are ‘earthed’ (which should be 0V) rises enough to upset the ECU. They may even share the ECU return path.

If the control (switches) of the wiper and blower are in the + supply to both – then a simple fix might be to locate the 0V returns and splice in an extra earth connection to them.
Other than that, check all chassis electrical grounding/return connections for corrosion which may indicate a poor electrical connection.

[shero101]

Thank you all so much for the detailed and helpful suggestions. We will look into to further.