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ST170 Aircon engine cooling fan draining battery

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Hi guys

First post here and really hoping you can help me.

I drove our Focus back from the tyre shop yesterday and parked up no problem. When I then went back out roughly an hour later I could hear the engine fans on which I thought was strange. I then noticed I couldn't unlock the car with the remote key and found the battery was dead. I then disconnected the battery to stop it and since reconnecting it, I found the relay/fuse F6 Aircon engine cooling stops the fans blowing if I remove it. I tried to replace it with another 30amp fuse from the box, but it still continued.

Now the aircon is off in the car and actually has not worked for a few years. It might have been on the windscreen dial though (which I understands turns on the aircon even though the AC light is off). Yet I have now turned the heater dial to 0 so it is off, but the engine fans come on straight away as soon as I replace the relay F6 with the engine completely off.

1.) Has anyone come across this before and know where the issue is?

2.) Can I leave the relay/fuse F6 completely disconnected and then jump start the car to drive it? Ie does the fuse only control the aircon which I will leave OFF or is it not that simple and I will risk the car overheating or worse?

Much appreciated for any advice or tips?



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Okay I managed to jump it earlier leaving the fuse in and fans were really noisy again. I let it run for a good while and took it for a quick loop around the block and seemed to drive fine, but I noticed this temperature gauge on the left in the picture below didn't move at all from the bottom the entire time. To be honest I am not the most mechanically minded, so not sure if this is normal as it is my wifes car usually.

Anyway after turning the engine off the fans continued to run and I have removed the fuse for now not to kill the battery again.


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19 hours ago, GingerFlame said:

It's possible that

The relay is faulty

Your temp sensor is faulty

www.yorkshiredetailing.co.uk - approved resellers of the Highest quality Detailing & Valeting supplies

Thanks mate for replying. I think the issue was the radiator fan switch. After someone suggesting it, I cleared a small bit of gunk off it and gave it a good wiggle whilst trying to remove it and hey presto the fans stopped and has seemed okay since. I am worried it is too simple a fix, but fingers crossed and I have ordered a replacement radiator switch to be on the safe side.

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