Did a couple of long runs in the defender yesterday (1.5 hours) and left the car on the driveway. Around 6 hours after sitting it started making a high pitched electrical squeal from the Engine bay. Kind of sounds like a transceiver.
It keeps going even when the ignition is off, only way to get it to stop is by disconnecting the battery. When you turn the ignition on it becomes lower pitched so it is somehow affected by current draw on the battery.

The engine still starts and runs fine with no odd behaviour, battery voltage is reading about 12.26V. You can’t really hear the sound while the engine is running but it is still happening.

Pulled each fuse out individually and no dice, anyone have any idea about what it could be?


attached a video for reference - this was when it started and was quite loud, after 15 minutes it got quite a bit quieter, gets a lot louder when the hood is up.

Horn?
Old fashioned whistling kettle?

Electric cooling fan maybe, or aircon fan or heater fan.

Yeah none of the belts are spinning though and it is constant which is the weird part (Even when car is off and immobilised). It’s gotten a lot quieter now after leaving for a few hours. I’ll leave it overnight and check the battery in the morning with an update.

Faulty BBUS?

SnowBored said:

Yeah none of the belts are spinning though and it is constant which is the weird part (Even when car is off and immobilised). It’s gotten a lot quieter now after leaving for a few hours. I’ll leave it overnight and check the battery in the morning with an update.

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Non of the electric fans are driven by the belts, I once had an electric cooling fan on a Volvo stick on and flatten my battery, whatever yours is sounds like it has a bad bearing or catching on something as well as being stuck on, when my fan stuck on which I discovered after charging the battery and refitted it and heard the fan running, I had to pull the fuse to stop it, which in that car was 50 amp, once fuse put back in it worked ok. After thinking more your noise might also be a faulty alarm.