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91 V6 Cooling Fanso

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Old 08-22-2008, 11:07 AM
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Default 91 V6 Cooling Fanso

My 91 Camry 2.5L V6 cooling fans both turn on when I start the car in the morning (cold). Is this normal? I though the fans were supposed to stay off until the engine warmed up then turn on. Does anyone know how the fans are supposed to operate normally?


thx....
 
  #2  
Old 08-22-2008, 12:15 PM
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Default RE: 91 V6 Cooling Fanso

Electric or hydraulic fans?
 
  #3  
Old 08-22-2008, 02:17 PM
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Default RE: 91 V6 Cooling Fanso

Sorry, there are 2 electric fans.
 
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Old 08-22-2008, 06:35 PM
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Default RE: 91 V6 Cooling Fanso

The fan should turn off if the coolant temp below 185F.

The coolant system has a temp sensor on the engine coolant inlet from the lower radiator hose. This is the inlet at the front of the engine behind the acc drive belt

The sensor could be bad. The wiring is differant, if the plug to the sensor is removed the fans should turn on.

The sensor should have the following resistance:

Approx 1.53K ohm at 176F
Approx 1.18K ohm at 194F
Approx 1.03K ohm at 203F

Coolant temp below 185F fans off.
Coolant temp 185-194F low speed.
Coolant temp above 194F high speed.

The fans have a low and high speed setting based on sensor resistance (coolant temp).

If there is an open wiring circuit the fans will also turn on.

Also check the fan relays (3 of them) for shorts. Location is in a box on drivers side of engine compartment chassis about where the battery is.

Don't know what the box is above the fan.
 
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Old 08-22-2008, 09:37 PM
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Default RE: 91 V6 Cooling Fanso

Both fans constantly run at all temps, cold, warm and hot. I check the sensor with an ohm meter and it reads 4K ohms. You said is should be closed which tells me that it should read 0 ohms. Is the sensor (near the T-stat) the same one as on the inlet (top of motor), the electrical connectors are the same. If so, I have a spare I can swap the lower one out with the top one. I did swap out all three fan relays too and fans still constantly run.

Question, there is a small black transistor-like unit (with 2 wires) on the passenger side fan (top). What does this do?

One more thing, I tested both the lower sensor (near T-stat) and the upper one above it (on the outlet, top of motor) by putting them in in a cup of boiling water. While cold they read 4k ohms, when immersed in the hot water they slowly decreased in resistance to about 1.5k ohms.


Thank you for your reply, I will do as you suggest and look for an open in the wiring.
 
  #6  
Old 08-23-2008, 12:23 AM
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Default RE: 91 V6 Cooling Fanso

See revised first post above for more info.
 
  #7  
Old 08-23-2008, 07:27 PM
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Default RE: 91 V6 Cooling Fanso

Toyomho,

Thx for the great info. I finally found the problem. There is a fan control amplifier located behind the glove box. There are 2 there, it is the lower one. I went to a junkyard and replaced it and now the fans work as you described. It was not the sensor.

Thank you again for the replies.
 
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