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Old 04-23-2012, 05:29 PM   #1 (permalink)
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Default Radiator Fans Not Turning On

I have a 2000 Ford Taurus Wagon with cooling system problems.

Thought Id check the fans to see if they were doing their job, and after driving it around and then letting it idle in the driveway I didn't see them come on.

Here is what I have done so far:
- Turned on MAX A/C no fans
- Tried jumping the wires going to the radiator temp sensor, no fans
- Checked for power going to the temp sensor, neither leg shows any voltage.
- Supplied voltage to the fans directly, both work.
- Checked my relays by swapping the high and low speed relays with the starter relay and all three started the car.
- Checked fuses, and also read 12volts at the live leg on fuse receptor

Any guesses? THANKS!
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Old 04-23-2012, 06:27 PM   #2 (permalink)
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Alright, so can I confirm the 40A fuse (#9) was good? Also, can you confirm you have +12V in two of the pin sockets for the low and high relays with the key on?

Can you also confirm you tested the coolant temp sensor with two wires and not the sender for the temp gauge with only one wire? With the key on you should see 5V on the light green/red wire with the sensor unplugged. If you don't see 5V, you either have a wiring issue or a bad PCM. If you want to check for a short to ground, check for continuity to ground on the green/red wire.
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Old 04-24-2012, 09:10 PM   #3 (permalink)
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behlinla, thanks for the quick response

Withdrew the 40 amp fuse from #9 and tested it with my ohm meter, it conducts power. I then tested the socket and got 12v on one of the legs.

To test the relay circuits which socket do I test 87? Should only one socket have +12v or two?

I tested the coolant temp sensor with the two prong lead. Its the one that is attached near the bottom of the inside radiator. I am not even sure where the guage sensor is.

The car starts and runs, does that rule out the PCM? If not how would I test it?

If I have a wiring issue, how do I begin to diagnose that?
I think I am in bad need of a wiring diagram. Havent had much luck with Google. Any resources?
Is alldata.com any good?

Last edited by 12characterz; 04-24-2012 at 09:32 PM.
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Old 04-25-2012, 04:50 PM   #4 (permalink)
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With the key on, you should have power in two sockets for both relays. 87 should have power from the fuse in both cases, but then you will have power on 85 for the low speed and 86 for the high speed.

Coolant sensor is in different places depending on which engine you have. Do you have the OHV or DOHC engine?

Here is the wiring diagram: http://www.revbase.com/BBBMotor/Wd/D...7-69d72a65409d

Make sure the PCM power relay is closing and you're getting power. You might also check fuse #2 (30A) that powers the relays.
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Old 04-25-2012, 05:15 PM   #5 (permalink)
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I included a picture of my engine, it is a replacement from another used Taurus, this is how I bought it. The vin designation on the body is "U", does this engine match that? Or should I be looking for parts under a different designation?

I did some poking around with the multimeter and these are my results.
All results are with key turned "on" and meter grounded to engine block.

Wires to temp sensor: both showed 2.75 (I would think only one of these would have voltage, the 5v you mentioned)

Wires going to fan: All three showed same 2.75v (Something wrong here because I thought one was a ground)

Low Speed fan circut: 12v at sockets 86, 87, 85
High Speed fan circut: 12v at sockets 86 and 87
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Radiator Fans Not Turning On-dscn0727.jpg   Radiator Fans Not Turning On-dscn0725.jpg   Radiator Fans Not Turning On-dscn0726.jpg  
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Old 04-25-2012, 05:54 PM   #6 (permalink)
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Thanks for the pics. You have the 3.0L OHV Vulcan engine. Coolant temp sensor is going to be located sort of below and behind the coil pack on a tube coming out of the thermostat housing. Look for the light green and grey wires.

2.75 is an odd voltage. Are you sure you didn't mean 12.75? Is the 1 segment on your DMM working? If it was 2 volts and not 12, then you might have a bad ground. Everything grounds back to G105, which is located on the left fender near the air filter. You should check that ground.

Voltages measured at the relays are good. This system is odd in the fact that it has an brake relay that switches the ground for the fans on and off. The brake relay is located in the other relay box between the battery and the fender. If that's sticking, then you won't have a ground. So I wanted to ask you how exactly you tested the fans by providing power? Did you provide your own ground or not?

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Old 04-25-2012, 06:30 PM   #7 (permalink)
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You can also have a fan resistor go bad, all of your relays and fuses will be intact but the fans will not come on. Check your fan resistors as well, they are mounted to the fan shroud or on the subframe near the fans depending on what year you have.


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Old 04-25-2012, 06:35 PM   #8 (permalink)
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Fan voltage dropping resistor is only for the low speed.
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Old 04-25-2012, 06:37 PM   #9 (permalink)
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Is the coolant temp sensor the one that shows on the dash gauge or the one that controls the fans?

I have included pictures of the thing I thought was the temp sensor that controlled the fans. It is located near the bottom of the radiator. This is the one that was plugged into the two prong lead I showed in the picture above.

I am certain I was getting 2.5-2.8 on both prongs on that plug as well as all three terminals on the fan plug. (The two shown in the picture above)

I have also included two pictures of the area near the thermostat housing, is one of these the CTS?
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Old 04-25-2012, 06:40 PM   #10 (permalink)
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@ SONic67 Correct, but the low speed is the ONLY speed that comes on initially, High speed is only activated if the vehicle is hot or overheating. At least that's how my bull works, take a look at the attached wiring diagram OP, this may help.


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File Type: pdf Cooling fan Circuit.pdf (149.8 KB, 440 views)
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