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  1. #1

    Default Cooling and condenser fan. Need some assistance on troubleshooting.

    1992 Celica ST, 1.6L Manual Transmission. Sorry in advance for the long post.

    The radiator split open and blew the top off last week. I replaced it and did troubleshooting. I don't think my condenser fan has ever run so that's a secondary problem. Right now my cooling fan doesn't seem to come on while warmed up and idling. Or driving. Here's what I've done so far.

    1) Found no continuity on Fan Relay 1 with 12V applied, so replaced relay.
    2) Replaced radiator, along with new upper and lower hose.
    3) Most other coolant hoses replaced over the past few years.
    4) Replaced multiple hose clamps along the way.
    4) Replaced water pump, with timing belt job, 2-3 years ago.
    5) Rebuilt A/C last summer and still comes on instantly and runs cold.
    5) Replaced Coolant Temp Gauge Sender (spade end) and Coolant Sensor for ECU (two prong connector). Neither probably necessary. Purchased from Autozone.
    6) Added T-FLush kit to heater core inlet and flushed thoroughly.
    7) Added proper mix of coolant and water.
    8) Performed block test with blue dye never turning yellow/orange.
    9) Performed Radiator pressure test with no leaks.
    10) Changed oil, oil filter, air filter, and fuel filter (cause it was time).
    11) Bought a Beck Arnley Thermo Switch for the fan, Part # 201-1720.
    12) Checked all fuses and only found the CDS fuse with no continuity.
    13) Replaced thermostat with OE 180-degree replacement.

    The cooling fan comes on when I disconnect the connector from the thermo switch. I've tested with both the old and new Switch.
    Last edited by nerlins; 07-05-2019 at 01:32 PM.

  2. #2

    Default

    There are 3 temp senders in the system:
    - single blade provides signal to guages
    - double to provide data to the e cu
    - double to control the radiator fan.

    The circuitry for the radiator is set up to keep the fan off by use of a special relay that is normally closed. When the sender is cold, it provides a connection to ground which opens the relay and turns off the fan. Once it gets hot, the sender breaks the circuit and the spring in the relay closes the relay turning on the fan.

    Also, in the same circuit is the ac pressure switch. If pressure is good, it completes the circuit which pulls the relay open. If it gets too high, it still open the circuit allow the relay to snap close turning on the fan.

    With car on, you should have 12v at both relay point 1 and 4. With the car cold, and off, a ohm meter should show a connecting to ground on point 2 of the relay.

    The condensor fan is controlled through the ac system. When the ac clutch is engaged, it will send current to the condensor relay 3. The speed that it will come is defined by condensor relay 2. When a.c. Pressures are not high, current class sequentially through both fan motors so they come on slow. When a.c. Pressure gets high, the relay 2 switches allowing both fans to run in parallel at full speed.

    You can find wiring diagram for 90 here: http://bgbonline.celicatech.com/90ewd/index.html

  3. #3
    Senior Member underscore is a jewel in the rough underscore is a jewel in the rough underscore is a jewel in the rough
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    Default

    If it comes on properly when you disco the switch, either something is wrong with the switch or somehow that part of the rad isn't getting hot enough to trigger it.
    1992 GT-S // 1991 GTFour RC // 2007 Jeep Grand Cherokee CRD

  4. #4
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    Default

    It's not supposed to come on under most conditions. Your radiators death wasn't related to the fan.
    I really like the way aaawelder put it: "do not include yourself in this circuit"

  5. #5

    Default

    Hey guys, I had to let it sit for a month. I have been too busy. Honestly, I don't think I was waiting long enough for the new switch. My cooling fan now comes on. I also snagged the relays and other sensors off a Gen5 I know of; deep in the woods about 15 miles from me. So far the cooling and condensor fans come on with AC, after switching those relays. I think everything is golden for now. Fingers crossed.

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