Volkswagen Repair: Jetta Sensor Problems, ecu computer, obd ii

Question
QUESTION: Hi,

I have a 2003 jetta with a 2.8L and everytime you crank it up the overheat light comes on. The coolant sensor is working and doesnt show it hot.  The fans dont work now either so when I idle for too long it does overheat, but the overheat light comes on even when the motor is ice cold from sitting all night.  I changed the thermal sensor on the radiator already and that didnt fix the problem.  Also I came to a redlight and every light on the dash started flashing and beeping and then the car just died.  It cranks back up after this.  Do you think I need a new ECU computer or what? any help would greatly be appreciated

ANSWER: Mike,
 When you say you changed the thermal sensor, do you mean the thermostat or the temperature sensor?  Anyway, a bad thermostat or broken water pump could cause this problem.  The fans need to be fixed, but the car should not overheat immediately even without them.

Rick



---------- FOLLOW-UP ----------

QUESTION: I changed the thermal sensor not the thermostat.  It does not overheat immediately, the overheat light flashes though.  The car will be completely cold and not been cranked for days and light will come on as soon as you crank.  It doesnt have time to even possibly overheat before the light comes on.  Im trying to figure out what cause the overheat light to come on 24/7.  Im assuming it's an electrical problem.  Someone told me to change the computer but I would think there is another sensor besides the thermal sensor that would cause the overheat light to come on.  Maybe a relay?  Thanks

Mike

Answer
Mike,
 It is more likely:
- The sensor is not installed correctly.
- The sensor is defective.
- The sensor is not correct for the model.
- There is a short in the wires of the sensor at some point.

I would get an OBD-II scan and see what error codes might be in the ECU.   The ECU would be the very last thing you should replace; they are known to be extremely reliable.

Rick