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AMEDEE
AMEDEE, FORD TECHNICIAN
Category: Ford
Satisfied Customers: 21844
Experience:  ASE MASTER TECHNICIAN ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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Ford Focus ZX5 2002 ford focus engine cooling fans will not

Customer Question

2002 ford focus engine cooling fans will not work at high temp

it works when i turn on ac

2 ford dealers have tried to repair it unable to find problem

2 for computer analysis no help
Submitted: 3 years ago.
Category: Ford
Expert:  AMEDEE replied 3 years ago.


It sounds to me like you have a bad cooling fan resistor. THis is very common on this vehicle. You can run some tests to find out what is going on when the fans are supposed to come on. I would start by checking the Green/White and Green/Blue wires at the cooling fan resistor, located in the radiator shroud between the two fans, to see if they both show voltage. The GN/BL should have slightly less voltage than the GN/WH but should still be able to light a test light fairly bright. If the GN/WH has battery voltage, but there is nothing on the GN/BL, replace the fan resistor. If there is no power to the resistor, check for power to fuse F2 (30A), in the battery junction box with the low speed fan still commanded on. It should show battery voltage on both sides.


Potential Causes:
Fuse
Low Speed Fan Control Relay
Low Speed Fan Resistor
Customer: replied 3 years ago.

the resistor has been removed ttested and replaced. it was also tested in place found to be ok

 

the fuse tested ok

 

relay relay tested ok

 

???????????

Expert:  AMEDEE replied 3 years ago.
And what about the powers to the resistor?
Customer: replied 3 years ago.
the voltage was tested on both sides of the resister and a difference was noted
Expert:  AMEDEE replied 3 years ago.
So your positive there is power going into the resistor on the green/white wire when the fans are supposed to come on but are not?
Customer: replied 3 years ago.
i am positive that power is going to the resistor when the ac switch is "on" when the ac switch is "off" no power to resistor
Expert:  AMEDEE replied 3 years ago.
WHat about when the engine starts to heat up and the fans do not come on? Is there power going into the resistor then?
Customer: replied 3 years ago.
no
Expert:  AMEDEE replied 3 years ago.
If you supply power to this wire, do the fans work?
Customer: replied 3 years ago.
yes because with the ac on power comes to the grn wire and the fan works
Expert:  AMEDEE replied 3 years ago.
Is the computer grounding the low speed fan relay when the engine gets hot enough?
Customer: replied 3 years ago.

according to the tech at beach ford the answer is "yes" because his computer indicates that power is being sent to the unit but the unit is not working

 

? will the computer not send power to the unit if the resister is faulty? thanks for your patience

Expert:  AMEDEE replied 3 years ago.
The unit or computer actually grounds the cooling fan relay(s). It does not supply any power to the relay at all. It activates it by grounding the relay.

If the computer is sending a ground to activate the relay and there is no power to the resistor, then the problem is within the circuit and not the computer.
Customer: replied 3 years ago.
i dont know if the relay is being grounded or not. how can i check or verify this
Expert:  AMEDEE replied 3 years ago.
Just see if the relay clicks when the engine is starting to overheat. The computer will not ground the low speed fan relay until like 220 degrees or so. This means it might take a while for the engine to get hot enough for the computer to ground the relay. If you cannot hear it click, you can remove the relay and see if one of the cavities are being grounded from the computer. THis will tell you if the relay is being commanded on or not.
Customer: replied 3 years ago.
i have determined that the cooling fan comes on at approximately 260 degrees which is to high and that the temperature gauge indicates mid range which is obviously inacurate it should be in the red area. it acually popped the expantion tank cap off?????
Customer: replied 3 years ago.

i have determined that the cooling fan comes on at approximately 260 degrees which is to high and that the temperature gauge indicates mid range which is obviously inacurate it should be in the red area. it acually popped the expantion tank cap off?????

 

 

additionally after the cap popped off i observed the temp gauge (in dash) quickly jumped to the red area???

Expert:  AMEDEE replied 3 years ago.
So does the computer ground the low speed fan relay before the engine gets to 260 degrees?
Customer: replied 3 years ago.
No! it grounded (the relay clicked) at 260 degrees and that is when the fan comes on
Expert:  AMEDEE replied 3 years ago.
Well, there is two relays.. are you sure you are talking abou the low speed fan relay and not the high speed fan relay?

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