Question about 2003 Toyota Celica

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2003 Toyota Celica Rad fan works continuous. Heater is barely blowing warm air I feel like the two problems are connected. The Rad fan comes on as soon as you turn the switch...

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  • S Buchanan Oct 26, 2012

    Ok thanks for the info. Let me clarify. 1st of all all the engine cooling fans are running all the time. Changed temp sensor, checked all relays they seem to be ok. Could this prob be the multiplex computer?

  • You are very welcome Mrs Buchanan, Just make sure your daughter drives safely and keeps the vehicle well maintained. Best regards John



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Hi S, The fan is not controlled through or by the ECU. I suggest you check the connection to the fan temperature sensor. If it is disconnected the fan will operate. Refit the connector and make sure the connection is making good contact. If the fan continues to run make sure that the relay is not fused and that it is operating correctly. Regards John

Posted on Oct 26, 2012

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  • S Buchanan Oct 26, 2012

    John do you think the heater problem is connected to the fan keeping everything cool?

  • Hi S, Most definitely.

  • S Buchanan Oct 29, 2012


  • S Buchanan Oct 29, 2012

    we replaced the temp sensor and checked connection seems fine. Rechecked the relays and all fuses everything there is fine. Had someone mention that the ac switch could be hung up making the engine think that is overheating but that was fine also. Its strange that bothe the ac fan and the rad fan both come on as soon as you turn the switch. Any ideas would be so appreciated. We are at our wits end...

  • Hi S, The AC fan should only work when the AC is engaged. The engine cooling fan should run alone when the AC switch is disengaged. If both fans are operating I suggest that you check the circuitry of the AC control. The relays for the AC are housed separately from the other circuits inside a smaller housing. The AC condenser fan runs to radiate the excessive heat collected from the cabin and will engage as soon as the AC switch is pushed to the 'on' position. If both fans are operating it seems you have a problem with either the switch, the AC relays, (maybe one is stuck) or the circuit controlling the operation mode. Regards John

  • S Buchanan Oct 29, 2012

    ok we will check. Thanks so much for the info

  • Hi S, I'm taking a guess and asking did you buy this vehicle used and was the purchase recent? The reason I'm asking is that I have known of situations when someone thinking the fan should run all the time the engine runs have placed a bridge under the fan relays. The usual is a very short length of wire bridging the connection under the relay. It's worth a look. Regards John

  • S Buchanan Oct 29, 2012

    We just bought it used for our 16 year old daughter. We didnt realize the fans were running when we test drove but now that its freezing outside and needing a heater we have noticed.

  • S Buchanan Oct 29, 2012

    John I so appreciate all the info. Just a quick question....the possible wire would it be under the relay? Somewhere noticeable? Thanks

  • Hi S, Please let me know what engine is fitted to your vehicle? The older models have the temperature sensor fitted onto the housing at the back of the engine (and as your's is a transverse engine it will be above the gearbox. The newer models have the sensor fitted into the bottom tank of the radiator. Make sure that wherever it is, the connector is fitted correctly and that cables are intact. If it is disconnected the fans will run. To answer your question, open the housing for the relays. You should see one marked "FAN" pull the relay out and make sure the there has been NO bridge inserted between any of the connections. After confirming that take out the relay for the AC and do the same. Also make sure that there is no additional wiring giving direct power to the fans. The radiator fan should only operate when the engine temperature has reached just below half way on the gauge. The AC fan and the radiator fan should operate together when the AC is engaged. It sounds to me as if someone somewhere along the line has made a direct connection, either by cheating the relays or by giving the fans direct power. It's a shame I can't get there to help you in more practical hands on ways, but Africa is a long way from the States. You must be in the States if your daughter is driving at 16. Keep in touch and let me know how you're getting on. Best regards John

  • Reiterating: The bridge some guys use on the relay is usually on top of the connector where the relay pushes in.

  • S, Also try to disconnect the power connection to the AC compressor. Have a look and see if the fans stop in that condition?

  • S Buchanan Oct 30, 2012

    Wow John The Lord has lead me to you. Thanks for all the info. We will look into the ac compressor. Yesterday we took a look at the relays again but didnt see a bridge. My husband said that the transmission has been worked on and we wonder if they have done something...Not sure but we sure wish you were close lol. The engine is a 1.8l 2ZZ. Thanks again we owe you!

  • Hi S, As your husband suspects work to have been carried out on the gearbox and the ZZ series engine is fitted, ask your other half to look or feel on the lowest part of the radiator (the bottom tank) and make sure the temperature sensor is connected. Regards John

  • S Buchanan Oct 31, 2012

    John we have found something (I hope its a fix) yesterday we were running the ac circuit (thanks to you) and behind the right side headlight were the freon goes wer found a ac compressor switch as soon as we unplugged it both fans cut off. We are going to try and find a replacement and see what happens. Thanks again!!!!

  • Hi S, If the switch is an inhibitor switch please remember to evacuate the AC system before replacing anything and even when the system is evacuated wear safety glasses. Sorry if I sound abrupt, been attacked by a mosquito and got malaria. Regards John

  • S Buchanan Nov 09, 2012

    John, I wanted to thank you! that was the problem. It took a while to get a replacement went thru 2 before we got the correct switch. Thanks again!!!



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