I have a 2000 Pontiac Grand Am. It has two coolant fans at the radiator. I noticed that at 230 degrees the fans do not come on as fast as they should, and the temperature gauge creeps into the overheat range. I changed the temperature sensor, the relays and fuses. Can you help?
If the engine isn't showing any other signs of an overheat condition, for example, the radiator boiling over, then start by confirming the accuracy of the temperature gauge.
That's going to require the use of a scan tool to view the temperature reading being received by the vehicle's powertrain control module (the engine's master computer). The coolant temperature displayed on the scan tool being notably different than the temperature gauge (more than a few degrees) indicates a problem within the instrument cluster, which would have to be further evaluated before replacement.
Replacing relays and fuses is all well and good, but there are lots of other possible faults in one or both of the coolant fan circuits. The Grand Am is equipped with two coolant fans which operate in unison, mounted in front of the radiator and the air conditioner's condenser. Typically the fans are activated immediately when the A/C is turned on, but otherwise operate according to the engine's coolant temperature.
The fans have two speeds, high and low. Both should begin running in low speed when coolant temperature reaches 223 degrees F, and off when cooled down to about 217 degrees. The fans kick into high speed when additional air flow is needed through the radiator to maintain coolant temperature, on at 232 degrees and off again at 226.
There may be a problem preventing the coolant fans from engaging at high speed. With the A/C off, let the engine idle until the temperature climbs enough to activate the fans at low speed. They should either shut off when the temperature drops to 217 degrees, or pick up speed as the temperature continues to climb.
If high speed never kicks in and coolant temperature continues to climb, the high speed fan's circuit operation will require further investigation. If high speed comes on and goes off in a few minutes (with no boil over), the fans are probably working correctly and the gauge itself is inaccurate. If high speed comes on and stays on, while the gauge continues to climb, there may be an issue elsewhere in the coolant system, such as an obstructed radiator, stuck thermostat, air in the system, etc.