cooling fans not coming on

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  #1  
Old 03-24-03, 06:37 AM
cooksey
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cooling fans not coming on

Hello All,
I have a 1991 chevrolet lumina euro. 3.1 V6. The cooling fans do not seem to be coming on when they should. I have never seen them come on yet and the temperature gauge has hit 220 or so. I have tested both fan motors and they both work. My question is which sensor controls them? I have replaced both relays and the sensor under the thermostat. I think that there is another sensor on the motor somewhere that has something to do with the temperature controls but I am not for sure. Would it just be easier to direct wire the fans to come on when the car is started? If so would I need to do both of them or just one. Any help is appreciated.

Thanks, John Cooksey
 
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  #2  
Old 03-24-03, 06:50 AM
Joe_F
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No, do not direct wire the fans. Fix the problem. Find the break in the wire or bad sensor causing the problem.

Use your service manual's wiring diagram or autolibrary.org to guide you.
 
  #3  
Old 03-24-03, 12:05 PM
redneck
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Do not believe temp guage. This motors are designed to get very hot. Do the fans ever turn on? Did the car ever overheat? I had a '88 IROC that would go to 220-230 on the guage before fans would turn on--GM garage said they are designed that way to pass emssions, I could not live with it, and wired the fans to a switch under the dash. My current work car--'91 3.1 beretta, will also get very hot on the guage before fans turns on--I found that by leaving the ac or defroster on when it is hot out will kick the fans on earlier--course my ac quit years ago!
 
  #4  
Old 03-24-03, 01:58 PM
Joe_F
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Yes, the A/C will bring the fans on at once. Have you tried that?
 
  #5  
Old 03-24-03, 02:04 PM
cooksey
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Cooling fans

Yes I have tried the air conditioner. They didn't come on then either. Does anyone know which sensor it it that controls them? I think there is one on the back side of the motor on the drivers side that has one lead wire coming off of it. That is the only other one I can find listed at any parts house. If I unplug the coolant temperaure sensor they will come on but so does the check engine light and it runs very rough. Any help appreciated as always.

Thanks, John Cooksey
 
  #6  
Old 03-24-03, 02:31 PM
Joe_F
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Are you sure you're not talking about the O2 sensor?

I would change the coolant temperature sensor as a matter of course. It controls the fans in many cases on GM. It might be your problem.
 
  #7  
Old 03-24-03, 05:18 PM
cooksey
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cooling fans

Not according to what I can find out it is not the O2 sensor. According to the web site that you have posted to check it says there is another sensor but doesn't say were it is located. The parts store came up with it on there system.


Thanks, John Cooksey
 
  #8  
Old 03-24-03, 05:25 PM
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the fans will not come on till the tempurature is around 230 like was said previosly they are designed to run this hot and is not an actual problem, there is two temp sensors on this car the single wire one you are reffering to is for the guage on the dash, the 2 wire one wich you have already replaced is the coolant temp sensor for the computer when the computer gets a reading of around 230 it will energize the fan relay to turn on the fans.
 
  #9  
Old 03-25-03, 12:39 AM
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The fans on these cars are not controlled by one sensor. The coolant sensor is only part of the system.. The A/C Sensor, Intake Air Sensor, and the MAP sensor also feed information in to the ECU that it uses to control fan. So it could be any wire in that system causing the problem, or any those sensors. As the other posters have stated, the fan might not turn on until the 200 degree range. I would make sure you have a “problem” before you kill yourself trying to find it. If you really want to have it manual put the fan on a switch, but keep in mind that an engine will not run right if it is to cold either.
 
  #10  
Old 03-25-03, 12:06 PM
redneck
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Yep, even as far back as 1977. I recently had a very low mileage, 400, 4spd Formula firebird, that I put a 160 degree thermostat in (colder is better) The engine did not get hot enough to open the heat activated vac. switch in the air cleaner--and would only suck air off the exhaust manifold! Severely restricting airflow at WOT. Replaced the thermo switch--same--finally figured out the 160 thermostat and newly rebuilt 3 row rad. worked too well--went to a 180 and all was well!
 
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