I recently purchased a 07 550i with 90000 miles and seems to be in really good condition. Last week the car started overheating. It is pretty odd though. It's only overheating when it's hot outside and will stop overheating if I turn the heat on. I have probed the relay going to the fan and it is receiving power. It kicks on when I turn the AC on only when it's cold outside. When it's hot outside it seems that the fan will not turn on. I probed the wires while hot outside and still getting power to the fan. Anyone have any input? Wondering if it may be the temperature sensor or maybe when it's hot the fan shorts out? The oem fan in 700+ and others are still expensive! Should I try temp sensor as it's only 20$? Any help would be appreciated!

thanks

 

Its the fan unit. My '07 550i died in the exact same way.

Call TLS Auto Recycling. They sold me a fan unit for around $350 a couple years ago with a 1 year warranty. I can vouch for them as I live in Sacramento, and this auto recycler is part of a huge "wreckers mall" out here. They've currently got 4 E60 550's in the yard, so hopefully there's a fan to pull for you.


https://www.tlsautorecycling.com