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No fans, No overheating!

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Pixels, Jun 22, 2009.

  1. Pixels

    Pixels New Member

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    If the thermostat and the cooling sensor are not working for whatever reason, the fans will not work, is this right? and then I will never know if the car is overheating, right?


    All the dashboard lights should turn on for couple seconds when I start the car, I don't remember seeing a heat light on the dash board with the other lights like VSC and brakes light and Airbags...etc. where is the overheating light located?


    if we said that the heat light goes off as all the other light on the
    dashboard when you start the car, dose this means that the thermostat and cooling sensor are working right? in other way, for example, If the ABS light don’t go off when you start the car, dose this means that the ABS is not supported and not working and almost dose not exist at all?

    I just replaced fans yesterday, AC and radiator fans. sure 100% my fans was bad but how come the car never over heated and never give me a sign of heat? also after replacing the fans how am I supposed to test it and make sure they are working?

    I drove it 2M and the fans never went on, there was no traffic and weather was cold.

    do you guys think the problem is heat or cooling sensor or thermostat related?
     
    #1 Pixels, Jun 22, 2009
  2. northwichita

    northwichita .

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     //////////////////////////////////////////

    Not clear, why exactly are you sure the fans were bad? They only will turn on when the car needs them, and this car doesn't put out a lot of heat. (although simply turning on the a/c at a stop should be a simple test to see if the engine fans turns on shortly) Interested in your car's symptoms, engine codes, keep it simple, and yes , the car isn't exactly made for the dyi'er to troubleshoot without a Scanguage type computer to help you.
     
    #2 northwichita, Jun 22, 2009
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    A simple way to test the radiator fans is to apply 12VDC to the fan motor terminals and see whether the fan spins or not. As northwichita stated, the fans should spin up when the A/C compressor is running.

    I believe that a warning icon will appear in the MFD if the engine is overheating.

    If you believe the coolant sensor is not functioning, you may remove the sensor and place it in freezing water first, then boiling water, and finally room temperature; and measure the resistance of the sensor under these various conditions. The repair manual will provide the spec, with higher resistance produced at lower temps. Freezing temp will result in ~10K ohms while boiling temp results in ~200 ohms.

    The engine thermostat should start to open at ~82 degrees C. Once you have driven the car on the freeway for a few miles, you should be able to put your hand on the radiator hose leading to the thermostat housing and feel engine heat. This proves the thermostat is open. If you have an infrared thermometer you can measure the temp of the radiator hose and this will give you a clue as to the temp of the coolant within.

    I also am wondering what causes you to think that your car needs service to begin with. DTC P0116 will be logged if the coolant temp does not increase after the car has been driven four minutes.
     
    #3 Patrick Wong, Jun 22, 2009
  4. JimN

    JimN Let the games begin!

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    In some 3 years/38000 miles with the grill blocked my fan hasn't started. Highest coolant temp I've seen is 198F.
     
    #4 JimN, Jun 22, 2009
  5. andyprius

    andyprius Senior Member

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    Generally, when the engine overheats, you know it, Prius or other. I often feel the temperature of my hood and compare it with my wifes Honda. The difference is astounding! No matter what kind of trip, length or outside temp, the hood of the Prius is always comparitively cool to the touch. I don't know how Toyota does it, it's as though the engine never turns on. 70K miles on car now. Unless one has specific symptoms along with proven codes &/or a failed part, buying parts randomly can be cost NON effective.
     
    #5 andyprius, Jun 22, 2009
  6. dogfriend

    dogfriend Human - Animal Hybrid

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    #6 dogfriend, Jun 22, 2009
  7. Pixels

    Pixels New Member

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    __________________________________ _

    I am sure that the fans are not working. I bought the car 2 months ago, 04 with 85 KM on it, I bought it with no cold air from AC, replaced the AC amplifier and the cold air worked and every thing went good for a while, until I noticed a weird smell after using the AC cold, the _ smile dose not come from inside the car_ so I saw that one of the radiator fans was cooking. So replaced both fans which was a hard job.

    Now I am wondering after I replaced the fans if they are working, because I noticed that some one before me have done dirty job in the harness. And this made me think maybe the sensors and thermostat is not working too since the fans looks that they was bad long long time ago, looks like it was bad 2 months or 3 before I bought it.

    oh well, it was a bad bad deal anyway. Man, all kind of caution lights on the dash board was glowing like christmas lights, ABS, VSC, (!) Brake, Check Engine light, and the Red Doom Triangle, even the MFD Screen thing used to say " The P lock Mechanism is in up-normal position, park your car in a flat space and apply the barking lock completely" this little MFD massage toke at list 30/H of my time.

    I basically had every caution light or massage that is posable on this car.

    I had to fix every thing my self and I am done with every thing, except for couple little problems to snack on here and there, the dealer estimated the work on the car for over $16K, Yep 16, so I had to do it my self. and I loved it and will stop graphic design and will do hybrid mechanic but in professional manners.

    the ppl who sold it to me was just desperate of fixing it because of how much problems it have.

    Now the question is: do I need to look at the thermostat and sensors or no? don't forget that as I said the car was missed up before? don't forget that now I have no error light or caution lights or triangles at all even when I had bad fans I never got an error for it! bad fan and no error to show!!
     
    #7 Pixels, Jun 23, 2009
  8. dogfriend

    dogfriend Human - Animal Hybrid

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    Thermostat and temp sensor for the fans are separate issues.

    The thermostat should be checked for correct operation by verifying that it opens at approximately 82°C. Patrick had a good suggestion to use an infrared thermometer if you have it, or at least feel the top radiator hose for warm coolant after the car is warmed up.

    The temp sensor could be checked by measuring the resistance at various temps as Patrick suggested earlier.

    Bear in mind that a couple of us have pointed out that the radiator fans typically don't turn on very often if at all; if the thermostat and radiator is in good condition, the engine tends to run cool even in hot weather - as I posted above, I have never observed the coolant temp hot enough to require the radiator fans to turn on. I have been using the Scangauge to monitor coolant temp for about 1.5 years and with ambient air temps up to about 105°F (40°C). That is the reason that you did not get a warning with a bad fan; the coolant temp was still in normal range.
     
    #8 dogfriend, Jun 23, 2009
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