I noticed today that one of the fans on my 2000 S40 does not turn on at all. It's the one on the driver's side,with the larger radius. Is that the Cooling fan or is that the condenser fan? Tks

As far as the cooling fan it does work! Put it face to face with other car and never went on,while the 2004 car went on after a while. Took it for a drive and when came back cooling fan was on and off as it s/b. I guess it takes longer to reach temp to kick in the 2000 car vs the 2004.
Fuse was ok. Car does not pass normal operating temp,no overheating .Nothing else I can do,I guess. Just hoping that was a fluke thing.

If I were designing a car with two fans, the larger would be for the antifreeze and the smaller one for the AC. Easy enough to check, turn off the AC and see what happens. At cold engine start, neither of the fans should be blowing. When the coolant reaches 220F, the large fan should kick in.

The small fan should be enough to keep the engine and AC happy enough.
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My back feels better when I sit in a Volvo seat

That"s what I thought but just wanted to make sure.
Is that I have a problem with engine cooling fan on my 2000 S40. It never comes on! I have not experienced an overheating problem,but I only have been driving short trips lately with this car.
I noticed it yesterday as I experienced a strange incident the day before. Drove the car for some 4 miles with A/C and radio on in slow traffic and 2 hours later the battery was dead. Few days before my wife drove the car for 40 miles in heavy traffic with A/C and radio on and some lights came on in dash as she reached destination. Drove back some 4 hrs later no problem.
So after what happened yesterday,I jumped it ,came home and charged overnight. Checked it this morning,normal,did Load test with a friend got a 14.2 volt reading,charging ok.
Just before I was ready to do a drain battery test I discover the cooling fan not working. Got the other car a 2004 S40 put them face to face,started both and the 2004 had cooling fan running some 7 min later. The "problematic" 2000 never got it going for some 15 min!
Something is wrong with this one! I understand there is a fuse for it that I didnt check yet. But do you think the problem with fan could have caused the battery drain?
Sorry for lenght of story,but wanted to be as precise as possible. Tks for yr input

In the engine compartment fuse box: #7 is for condensor fan 10amp, #15 is for coolant fan 30amp.

Remember, the coolant fan is triggered by the ECT sensor by the thermostat. Earlier models also had relays on the fan shroud, usually reliable.

If your OEM thermostat fails, it will probably fail in the open mode. This is noticed by very slow heating, watching the instrument panel.

Battery drain? Only if the colant fan runs for an excessive time after the engine is turned off. How old is the battery?
How many miles on the alternator? Could it be worn brushes?

Too bad we don't know which lights came on.

I really dislike these new cars that have no gauges, showing my age a bit!
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My back feels better when I sit in a Volvo seat

I'll have more answers tomorrow. For now Thermostat,ECT sensor and Cooling,Condenser fans were replaced 2 1/2 years ago.
Battery is an Interstate Mega Tron Plus 700 CCAs about 5 years old. Alternator I have no idea if it was ever changed. But the output on it is above 14 volts...
as for lights that came on she mentioned the air bag light,but women never know exacttly what goes on with cars. I'll revert tom with more info on my findings.tks