Why would a car stall after the radiator fan turns on?

A critical voltage drop probably is occurring at either your fuel pump or the electronic ignition module (computer), when a large current load is being drawn by the fan motor. Wait until it stalls and won't start, and then simply umplug the connector to the radiator fan, and see if this "cures" the problem. If so, then check the voltage at the fuel pump wires or relay (should be at least 12 volts with engine running). The control signal to the relay comes from the ignition computer, which shuts down when a critical low voltage is reached (perhaps 9 volts or so). If the fan motor is the problem, and not turning freely,it would be drawing excessive current flow, and need replacement. Otherwise, the problem may be a corroded wire "take off" from the battery "pos" red wire or battery post, or a bad connection at the fuse block, etc. such that the fan motor is "stealing" current flow downstream from a high resistence connection, leaving insufficient current to run the fuel pump. // Jake

good luck // Jake

AnswerThis problem is a pain. A 93 sunbird SE with 3.1L did the same thing to my wife and after throwing lots of money on everything like plugs and sensors (from the dealer techs), it came down to a TCC. The car would warm up fine and for the first few miles be ok (on cool days). On warm days the car would run ok until she got into stop and go traffic. The fan would come on (coincidence?)and the car would suddenly shudder and even if she put it in neutral it would stall. The advice of making sure all the wiring is intact as well as the fuses and the fluids checked out is a good idea. There is a Technical service Bulletin with GM. I .

Good Luck

What is a TCC?

Answer

Torque Conveter Clutch.