Cooling fan doesn't come on when tem gauge goes up. have 2 turn on defrost. why?

Cooling fan or cooling fan sensor

recheck water pump and thermostat --check and test fans -radiator flow --and for possible head gasket failure

check terminals on the ECM
the circuit is when the coolant temp sensor ( not the gauge sender) reaches a predetermined setting , power is supplied to the ECM which in turn activates the fan relay and switches on the fan
there are normally 2 fuses in the circuit
the gauge sender is normally a single wire unit and the sensor unit has 4 wires to it

check the circuit to the tem p sender unit by removing the wire at the sender and turning on the ignition touch the wire to the head . The gauge should got o hot. This indicates that the wire is ok . Remove and replace the sender unit as it is shorting out inside and is not showing a resistance. The higher resistance __cold water --the lower the gauge reading. The lower resistance the more current allowed through so the gauge goes up

If you suspect a faulty ECT, use a scan tool when the engine is cold and see if the ECT matches the IAT temp.

It could be the thermostat but you need to check the fluid level and for any leaks (these could even be pin hole) first. If you have one of those infra-red temperature gauges you can check the temperature of the cooling system in the engine bay to double check. Generally the engine temperature should not go much about 90 deg C - this is when the electric cooling fans kick in - are these turning on?

if engine at long stand still,the engine temperature will rise about 190 degrees the cooling fan suppose to automaticaly turn on when coolant temperature sensor get hot it cause its resistance decrease causing pcm to send power to coolant fan relays and cooling fans, when you turn on AC the cooling fans suppose to turn on to cool down AC CONDENSOR, IF NOT AC WONT WORK COOLING FAN COOLS DOWN REFRIGERANT SO IT CAN RECYCLE THROUGH THE SYSTEM AGAIN.your cooling is suppose to turn on when engine at a sit still if vechicle not moving as coolant temperature rises at a set point the cooling fans will turn on cool down engine.cooling fans dont turn on when you first cold stsrt vechicle unless you have AC SWITCH ON.if cooling fans dont turn on when vechicle at a long stand still or moving along slow traffic.if coolant temperature sensor been replaced and fuses and relays okay have dealership check see if pcm driver circuit working faulty pcm will cause cooling fans not to turn on.

the temp seems to be fine. 80degrees celsius or less in stop and go traffic is normal,especially since the cooling fans are working and coming on at the proper time. the what seems to be running rough is another problem that doesn't seem to related to the cooling system temp. may want to check the spark plugs for worn electrodes.

the electric cooling fan for the radiator will not turn on when the engine reaches normal operating temp, its only supposed to come on if the engine temp goes over the normal temp. (around 220 degrees)
it is normal for the fan to come on any time the a/c or defroster is turned on.

MOST COMMON ISSUE WITH THE OIL LIGHT IS THE ENGINE OIL PRESSURE SENDING UNIT, REPLACE IT, ALSO 3/4 SCALE TEMP IS NORMAL, THAT IS WHEN THE COOLING FAN KICKS ON, ABOUT 230 DEGREE'S F.