After my wife turns off her 2002 S80 Volvo, there is periodic buzzing sound which lasts about 3-4...the cooling fan use to run after the engine was turned off...now it does not come on at all, however, the radiator fan runs fine when the engine is on...I was told by the Dealer that this should not cause the engine to over-heat...how serious is this? Thanks

http://forums.swedespeed.com/showthread.php?190702-Buzzing-noise-coming-from-engine-after-I-turn-it-off

Go to autozone,they will scan for free and tell you want is wrong.

the 2002 s80 did have a problem with the cluster. I have one and I love the car. I went on ebay and found the correct cluster to fix the problem. If the displays are going off and on, replacement is the only fix. The 3 sets of numbers on your "new" cluster must be an EXACT match with the old clusters numbers. In other words, the cluster must be for a 2002 volvo. If the numbers match, it doesn't matter what model the donor cluster came from.

This is normal. The fan will run even after the car is shut off until the engine gets below operating temperature. Most vehicles will do the same thing. Although I think thirty minutes is an excessive amount of time. Most could run up to fifteen to twenty minutes. If the car is retaining heat somehow this would cause it to run longer. Happy motoring!!!

If you are talking about the thermo electric cooling fan, its operation is independent of the car's electical system. It is switched on and off by the engine temperature. When you park, the engine heat soaks upward to heat the thermostat turning the fan on. It will run until the engine cools down and the thermostat switches it off.

Some cars are simply wired in a manner to run the cooling fan with the key off and the doors locked in order to keep underhood temperature from climbing way too high for plastic engine parts to survive.

Usually there is not a problem with a dead battery because the fan switch will shut off the fan hours before the battery dies. If your battery is dead after such an episode it's more likely that you need a new battery than anything is basically wrong with the logic or operations of the fan switch. But it won't hurt to check the operational temperature if that is needed.

If you re-wire the switch to only operate when the key is on then you run the risk of over temperature on all your plastic parts under the hood. Some high dollar engineer has staked his/her reputation on having the wiring as it IS. It bugs the heck out of me too but maybe it's better to live with it?

find cooling fan relay and replace it

You will need to have your engine diagnost to find the exact problem. Autozone will do it free and let you know what you need.

It might possibly be the vacum actuator for your break system.

This sounds normal. The engine cooling fan it set to contine to run after being shutoff. If you open the hood at some point and look at the layout, you will see the electric radiator fan in the front of the engine compartment, along with a note that says: caution fan may run w/o vehicle on.