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My Rad fan doesn't turn on anymore

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My Rad fan doesn't turn on anymore

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    My Rad fan doesn't turn on anymore

    I drive my 91 Da every day 40 miles a day. I bypassed the motor to 12 volt power and it ran. So the motor is still good. What else should I check for? Could these be the problem..."Radiator Fan Control Module" and/or "Engine Oil Temperature Switch", Or that sensor behind the coolant bleeder bolt?

    #2
    Fuse 21 -15A, [hot in run] rad fan relays coil power.
    Fuse 12 - 15A, [hot at all times] rad fan power.

    Rad fan relay...
    Black - ground
    Black/yellow - 12V+ when ign. switch on, [fuse 21- 15A].
    Blue - ground out when relay energized, [rad fan ground].
    Yellow/green - ground input from ECTS, [relay control].

    Engine Coolant Temperature Switch...
    Black - ground.
    Yellow/green - ground output, when coolant around 190 degrees F, goes to rad fan relay.

    Quick test, turn ign. on, unplug ECTS, ground the yellow/green lead, you can use a jumper from the black lead.
    If rad fan runs, replace ECTS. 94

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      #3
      Is the ECTS nearest to the oil filter?

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        #4
        All I can tell you is what my Haynes manual says, "it's on the back of the cylinder head, firewall side, just look at the wires, there should be a black and a yellow/green lead going to it. 94

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          #5
          Was lazy for about a year to tackle this problem. Now I feel motivated.

          Both fans (Radiator and condenser) are operating only when the AC in on. And only periodicly. As the AC still on, both fans stop for about 5 seconds then turn on and stay on for about 10 seconds then will repeat itself. But as soon as I turn off the AC, both fans will not come on at all even at operating temperature.

          Fcm- I haven't tried out your test on the ECTS yet. Need to find some long enough wire to reach the battery. Any comments ^ about this are welcome.

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            #6
            The A/C head pressure, [150-175 psi] is what triggers the condensor fan, if condensor fan turns on so will the rad fan, your problem is either the ECT switch or the rad fan control unit. 94

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              #7
              Did you try unplugging the thermostat switch sensor (located near the lower radiator hose connecting to the block) and use a paper clip to short the switch while your key is in on position to see if your rad fan turns on? If the fan turns on it means that the thermostat switch is good if not your thermostat is not opening or there is air in the system that you need to relief.

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                #8
                Originally posted by fcm View Post
                The A/C head pressure, [150-175 psi] is what triggers the condensor fan, if condensor fan turns on so will the rad fan, your problem is either the ECT switch or the rad fan control unit. 94

                OIC. I'll post up in April for an conclusion and update. I plan to drain/ fill coolant in April then I'll test the ECT. If bad I'll replace it. Hopefully its not the rad fan control unit. Is that known as the "fan timer" located under the dash board?

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                  #9
                  Yes, sometimes called "fan timer", we do not have that unit in CDM G2s or the engine oil temperatuer switch and by the looks of it the timer and oil temp. switch are only there to turn rad fan on, [ign. off] if oil temp is high.

                  As I said we do not have them, so realy they are just something else that can go wrong, that goes for the ELD also, we do not have then either, wonder why??? 94

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