The fan does not come on and the engine overheats

The air con fan comes on when the air con is engaged, the engine fan comes on only when the engine reaches operation temp. controlled by a temp. switch. on the block or radiator .

There are quite a few reasons the engine could overheat other then a failed cooling fan clutch. I wonder if the fan is always on because the engine is always running hot?
This condition may be caused by any of the following possibilities:
• Installation of an aftermarket grille.
• A plugged charge air cooler.
• Fan clutch not operating properly.
• Drive belt slip.
• An overfilled transmission.
• Turbocharger not operating properly.
• A plugged air filter

Hope that helps........

an engine will overheat if the rad cooling fan is not working, this will have to be check to see if its the fan motor, the fan relay. low coolant level, top up coolant check for leaks. could be head gasket problem, bad water pump(impeller worn).

did you first check all fuses???? that be 1st !!!
dead cold engine, I OFF the rad cap, is the system full? of AF?
is the AF/ tested at 50% with the $2 tool? "prestone tool"
Does the AF coolant look like Mississippi mud?
AF= Antifreeze SOLUTION (coolant)

is this the 3.7L V6? , ????? that be first. what engine option. of 4.
even a 2.8L diesel.

no, the PCM is not the problem(CPU the brain) not at all.
unless the fans die... on 2.4L engine. got 2.4?
first tell us when it overheats. ?

parked. stopped only?
moving fast? ever? overheat.?
both ways?
Does the fan kick on , as the FSM tells you,.???

2 engines, have a viscous fan clutch others have electric fan
until you post engine. we can not help.

is the radiator fins clean? free of junk? front to rear.
if yes, it should not overheat moving fast.
if it only overheats parked, the fan is bad.
or clogged rad tubes... (easy test ask,with $15 pyro gun)

there is a start..

check the fan relay

Cars usually overheat when the thermostat is faulty, coolant level is low, or the water pump fails. If your cooling fan on the radiator does not kick on shortly after the engine reaches operating temperature, you may have a bad cooling fan, cooling fan relay, or cooling fan fuse. If your engine is overheating, start by checking the fluid level, and installing a new thermostat.

A blower motor resistor is the device that controls a car's cabin heating and air conditioning unit's fan speeds. This usually won't cause the engine to overheat, your A/C fan may not function or only function at one speed. Here is a Blower Motor Resistor from Autozone: http://www.autozone.com/autozone/parts/2003-Ford-Focus/A-C-Heater-Blower-Motor-Resistor/_/N-jk8uvZ91tag

will try to help. the fan you replaced, was it the air conditioner fan? if so. then you need to check your primary fan. the one that does come on when the engine reaches operating temperature. make sure by starting engine, let the motor run and the temperature guage reaches the normal operating temperature.if the main engine cooling fan does'nt come on, then you'll need to check the fuse box under the hood. relays are black square plug in's they are marked and will[fan relays] tick when you turn the key on] if main engine fan does not come on when engine overheats, #1 fuse blown #2 relay bad #3 main cooling engine fan bad. note; the air conditioning fan will come on with engine running,when air conditioniing is turned on. when the a/c is turned off, the a/c fan will not be turning. hope this helps and as always, thank you for choosing fixya.com

The Fuse is No 37 in engine bay fusebox, for location see http://www.bluejag.co.uk however operation is quite complex , the fan control unit is located top left near the fans. The supply to the fans is a pulse width modulated signal from the control unit.

Run volts from battery to fan motor....if it turns problem is either in the fan motor sensor/electrical connector(corroded, etc.) or if equipped with a fuse possible blown but doubtful.

Is the fan now working? Your engine will continue to overheat if you have not fixed the fan. Check the fuse for the fan, connectors, and replace the fan if necessary.