What's wrong with the fan in my car?

Question

I have a '99 BMW 328i. Today, after driving about an hour, when I turned off the car, the fan kept running. This is normal, but it usually stops after a few minutes. Today it ran until the battery died. Turning the car on and off again made no difference. Running the car for five minutes and turning if off also made no difference. I'm assuming there's a switch someplace that is failing. Ideas? How brok will I be when this is fixed? :-(

Answer 1

Cooling fans run for one of two needs: to cool the engine or to cool the a/c unit. There is a pressure switch to cause it to operate for the a/c needs based upon the hi side pressure which builds when hot, usually located in the hi- pressure line near the radiator.

The coolant switch may be nearer to the thermostat. It works on an electric basis, unsure if providing ground to fan or positive current but if either are "stuck" in the run position, then you'll kill the battery.

Alternately, the battery could be going bad and this is the first sign. Does the battery feel "hot" to the touch on the sides after running a while? That could indicate an internal short. It would be worth while to also check the alternator. A good tech will save you money and cure what ills your 328i. This may involve some diagnostic time as electrical issues are somewhat more difficult to diagnose.

I owned a 1997 528i and had to replace the a/c compressor, belts, drier and idler. It was fun to drive but remember that this type automobile takes a lot of money to keep it operating, so I traded mine finally for a Jeep Liberty Diesel.

Answer 2

OK, first....find your relay. Second, check the coil on the relay. If it's constantly excited then most likely the thermal control sensor is bad. It supplies the information to the computer so the computer can turn the fan on and off. If the relay coil has no current flowing through it, then the contacts on the relay are stuck shut. In this case you would just replace the relay. For a cheaper relay go to www.mcminone.com vs paying 40 bucks for one from the dealer.

Answer 3

The fan is turned on and off by a switch that senses temperature. I would imagine it stuck and it's probably not very expensive, maybe you can even replace it yourself. I had a car that did the opposite. The switch stuck in the off position and the fan never did come on. It overheated as a result. Whatever you do, check the switch first. If it can stick on, it can stick off.

Answer 4

yup, its an electrical part which should be mounted on or near the fan Assembly, if your handy should not be at all a difficult thing to do, if not then or get a diagnosis of the problem, a 100 buck right there just to hook it up, but more than likely it is that simple sensor that may set you back a bill or two.

Answer 5

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Answer 6

you have a relay some where on this car that is sticking locate and find a person to file the contacts and your as good as new but if unable to fix a replacement will be in the range of $30.00-$85.00..

Answer 7

Check the cooling fan motor relay. It sounds like it's fuse open and needs to be replaced

Answer 8

there is a thermometer that tells the fan the car is cool enough and to cut off, It's broke (a simple switch) on a beemer it could cost you 40 to 400 bucks depending on.... who.

Answer 9

try unhooking the battery for 2 to 3 min. then hook it back up, this will reset the car computer.

Answer 10

Autozone is a good place to find answers. Maybe someone there has an idea.