BMW Repair: radiator and fan, coolant level, engine coolant

Question
My son's 1998 328i bmw was hit on driver's front side and among other things, the repair shop replaced the fan and radiator with non-OEM parts. About a week later a digital check engine coolant light came on. They said it probably is that the indicator/thermostat (wasn't there) didn't get changed and to bring it back in. My question is: Will non-OEM fan and radiator work? I noticed that the fan looks entirely different - no center fins that I saw on another bmw.

Answer
did the message say low coolant or coolant level low? if so, check the coolant level first. if the level is ok, then the coolant level sensor may be defective or the wiring for the sensor may have been damaged in the accident. the sensor is located under the coolant resevoir. it has a large plastic hex head nut. non oem will work