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Engine Cooling Fan Stays on

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by crustyoldgrizz, May 19, 2012.

  1. crustyoldgrizz

    crustyoldgrizz New Member

    The dealer replaced only Relay #1 Do you mean Relay #1 and Relay # 2 on picture they have open contacts and look the same.




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  2. bazar01

    bazar01 Member

    I would pull relays 1 and 2 and do a resistance check on the normally open contacts at terminals 30 and 87. They should be open and read infinity. If the contacts are closed which would read a low resistance value of 0-<1 ohm, replace the relay, the contacts are welded close.
    Post your results.
  3. crustyoldgrizz

    crustyoldgrizz New Member

    I pulled relays 1 and 2 and they read infinity. What I missed is that I usually Jump start the Sub. and drive around say 5 Km to charge the battery then shut off the engine. The fans don't start then but in 2 or 3 hours when the engine has cooled off it seems.
  4. bazar01

    bazar01 Member

    The PCM can do weird things on a weak battery. Have you had the battery load tested at an auto parts store?
    While the engine is idling, what is the battery voltage on the dash?
  5. crustyoldgrizz

    crustyoldgrizz New Member

    When first picked it up from Local dealer after New PCM they charged me $34.49 for "check battery, charge and test battery, ok".. so thought it was okey.

    The battery Voltage on the dash was 14 with two little bars past 14, hope You understand my attempt to explain.

    So the fan is running draining the battery and I have to move the truck in 1/2 hour or more so I pull relay 1 and let it lay there come back in one hour plug relay 1 back in without starting truck and fan stays off??
  6. bazar01

    bazar01 Member

    Well if that is the case, the relays are good, if terminals 30 and 87 read infinity. Can you reach under the fuse box and disconnect the wire from terminal 85 or 86 and run a wire to a toggle switch inside the cabin? It looks like the PCM is still providing a ground path to the relay coil even when the engine is off.

    Or you can move the 12VDC supply to relay 1 to a switched source, that way the fans will not run with the ignition switch in the off position.

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