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right radiator fan not working...please read this senario:

Discussion in 'Technical Q&A' started by groovzilla, Feb 22, 2004.

  1. groovzilla

    groovzilla Karting

    Nov 28, 2003
    117
    seattle, wa.
    Full Name:
    william
    installed the new thermo switch (thanks dave handa and ChrisfromRI) on my 79 308GTS..

    yesterday before installing the new switch i checked the fans by shorting out the wires at the radiator...BOTH fans worked fine....

    **please follow this....today after i installed the new thermo switch, i turned on the AC (while the car was running)for the first time to see if the right fan would operate...it did not operate...so i then turned the AC off and pulled both wire connectors from the new thermo switch and shorted them...the right fan does not operate..only left fan works...

    **is it possible that there is some sort of malfunction in the AC switch since it turns on the right fan??

    i haven't tested the right fan by hot wiring but it seems there is some sort of connection with the AC since i had never turned on before...

    any help appreciated..

    regards,
    william ceriale seattle, wa.
     
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  3. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    11,482
    San Carlos, CA
    Full Name:
    Mitchell Le
    THe aux fan is driven by 2 circuits, one by the AC circuit juice, and one by the thermal switch at the radiator. You may have solved the one, but not the other.

    There are two limit switches for the AC, a hi-pressure, and a low-pressure switch. Their function is to turn on the AC only if the AC system is charged to within those 2 limits for safety reasons. If your AC is not charged (like mine) there will be no electricity to the AC or to the FAN.
     
  4. groovzilla

    groovzilla Karting

    Nov 28, 2003
    117
    seattle, wa.
    Full Name:
    william
    i am sure my AC is charged and is cold when turned on....i will check that out tomorrow...

    i was told in previous posts that shorting the two wires at the thermo switch will run BOTH fans..

    is it possible that there is a loose connection or wire problem at the AC switch(s) for the fan???...where are these switches located??

    **also, what is the best way to test the right fan to make sure it is working properly..??

    appreciate the help...

    william c.
     
  5. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    11,482
    San Carlos, CA
    Full Name:
    Mitchell Le
    1. Connect 12V across the fan, if that runs, the fan is not the problem
    2. Shorting the thermal switch at the radiator should turn on both fans, if that works, that side of the circuit is not the problem
    3. That leaves the AC circuit to be the culprit, the problems could be the limit switches at the front of the car where the AC lines enter and exit. You should find some pressure switches there in line with the AC lines. And if the AC turns on and cold then at least the AC switch is not a problem. That leaves wiring to the fan. There is another relay driving the AC current for the fan. Do you have a schematic?
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    22,171
    Texas
    Full Name:
    Steve Magnusson
    william -- When you "short" the thermoswitch at the radiator you actually send signals to close two ...113 relays that independently supply power to the radiator fans (rather than your "shorting" action putting power directly on the fan motors). The RH radiator motor has another independent ...113 relay that activates it when the AC is on (and the thermoswitch in the radiator is not closed).

    If you short the thermoswitch at the radiator (key "on") and both fans don't run -- check the respective ...113 relay.

    If you pass the test above, but the RH fan does not come on with the AC -- check that ...113 relay.

    If something else happens -- please describe ;)
     
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  8. groovzilla

    groovzilla Karting

    Nov 28, 2003
    117
    seattle, wa.
    Full Name:
    william
    steve...are the relays located in the fuse bank???

    ....i'm not at my car or owners manual at this time to decipher where they are located...

    thanks...william
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    22,171
    Texas
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    Steve Magnusson
    Yes, those relays are located in the group of relays on the relay panel adjacent to the fuseboxes.
     
  10. groovzilla

    groovzilla Karting

    Nov 28, 2003
    117
    seattle, wa.
    Full Name:
    william
    since i have no way to test the relays(and they are inexpensive $15@) i just ordered a couple from T rutlands and should have them in a few days...

    i will install and let you know whats up...

    appreciate the help and look forward to the relays hopefully being the problem with the right fan..

    regards,
    william ceriale sea, wa.
     
  11. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    22,171
    Texas
    Full Name:
    Steve Magnusson
    william -- You're kind of jumping the gun! If the RH fan is dead when you jump the thermoswitch, just switch the ...113 relays for the RH and LH sides -- if the LH side goes dead and the RH side works than you can replace the relay with confidence. You could always just have a corroded connection at the relay...
     
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  13. 4re gt4

    4re gt4 Formula 3

    Apr 23, 2002
    2,279
    Roseburg, OR
    Full Name:
    Hans E. Hansen
    Also, if you still have the OEM Lucas fans, they can and will quit w/o warning. I had two crap out at once - or at most within a day or two of each other.

    But, obviously, check the relays first and hope that is the problem. Even if a new relay fixes things for now, it wouldn't hurt to schedule a weekend to O/H the fan motors. Cheap and easy to do.
     

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