Hi all. 

I recently purchased a 2004 XJ8 V8 SE Auto. Everything was going great until it started raining. While driving I turned the wipers on and the engine cut off. The car still had Electrics, but the engine stopped dead.

Would anybody have a clue to why this might be happening.

Hi Robert, never experienced this cut out in any vehicle before, but would suspect a connection between the rain and the cut out engine, to have an electrical sub plot.

It sounds like a water ingress to an important part of the vehicle's electrics which was "loaded" when you turned on the wipers - perhaps a coincidence, but worth looking for commonality in the circuit - like ignition on.

Did it restart afterwards, or has it remained "dead" since occurring? You state "the car still had electrics", what do you mean by that? Were the lights on at the time and remained on, did the dashboard light up, did any warning lights come up, are there any stored codes to be read?

N6 JMX

The car restarted and runs fine. But as soon as the wipers are turned on it cuts out, as if the ignition was turned off. But restarts and runs fine as long as the wipers are off. 🙄

Long shot, but does the car potentially have an aftermarket security system fitted, whereby the previous owner obtained the power feed from a circuit that included the wipers?

Wipers need the ignition on feed to operate, so potentially there is a short circuit occurring within the wiper switch mechanism or motor, that is taking out the ignition feed when activated. Try and find a good second hand wiper switch and substitute, or alternatively, access the wiper motor itself and disconnect the power supply, Then try the switching on of the wipers with the engine running to see if the fault persists. Outcome will point to the switch - if the engine cuts out - or the motor - if the engine continues to run as normal.

N6 JMX