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My radiator cooling fan no work unless the AC is on.relays ok new temp sensor.

(1996 Toyota Camry)
in King of Prussia, PA on November 16, 2013
I have to leave the AC on in order to get the radiator fans to run. Everything seems fine. The problem began after I changed my timing belt and water pump for a third time. The car has 229,000 miles. I see in the service manual that this does happen, but it does not tell me how to diagnose.
Displaying 3 answers & 14 comments
Popular Answer
on November 16, 2013
Does the engine get HOT without the ac on? Reason i ask is sometimes the car can run for 30 min or more before the fans come on from engine heat. But should not overheat. People often get confused about the cooling fan operation!!
on November 16, 2013
Yes, the car will overheat when stopped or parked for more than one minute. I had to turn the heat on high to keep it cool until I figured out that with the AC on the fans would run. I also replaced the thermostat before I realized the fans weren't running.
on November 17, 2013
Almost seems like it has got to be crud inside the radiator where this normally closed COOLING FAN SWITCH screws into and is not opening the switch circuit when the coolant reaches the correct tempture. OR there is a circulation problem. Unpluging the connector and then the fans run, is the same thing as opening the circuit!! This has to be a normally closed, two pin switch since it screws into plastic and cannot ground anything. Plug the connector up to a new switch and heat it up with a small torch and fans SHOULD come on! Otherwise the switch would not even be needed! That is just to help you figure out how I THINK it works. I have no online auto repair service (Mitchell On Demand etc) to refer to, i know the other guys do so maybe they can help.
of G. T. Service Center on November 17, 2013
I looked it up and tried to explain it to him in my reply.
on November 17, 2013
Ok, didn't read down far enough,,,,i agree!
on November 17, 2013
Thank you for taking time out for this. I understand quite a bit of cars and have worked on and built several. I must be missing something, or a wire is disconnected. I checked the relays and they both click showing operation. The radiator is about two years old and the cooling system is clean. Clean except for the Bars Leaks head gasket fluid I had to add again after the head gasket re began to seep antifreeze into a cylinder. I flushed the system again before adding sealant once more. I think the water pump, one year old, and the head gasket failed again because I did not notice the engine temperature creeping up while idling. I am patient and will continue to keep working on the situation. Thank you for putting into words how the relays work. Interpreting this knowledge and reading the wiring diagram will, at the very least, help point me to the problem. Thank you everyone and I will keep you posted of whatever my oversight has been.
on November 17, 2013
Head gasket could be the problem all together! Good luck with it!
of G. T. Service Center on November 17, 2013
Don't use bars leak it will stop up the radiator faster then eggs. Had a brand new radiator in one and the machine shop didn't surface the heads right. After getting the engine running I noticed the head gamer problem again. Was tired and put bars leak in it until I could tear it back down. What a mistake. It clogged the brand new radiator. Had to rod the new radiator to keep it from over heating. May be your problem. Flushing is not good enough.
on November 17, 2013
I have always worried about the clogging issue and would never recommend using the gunk. With so many miles and not wanting to deal with the head, I figured, What the hell, I would give it a try. It worked for over two years before these problems began to appear. I guess I will limp the car along for a while and try to solve the issue. That is until it maybe craps out. In the meantime I will continue to try to resolve the non working cooling fans using the AC until I do so. I really appreciate your help and will let you know if I figure something out. Thank you
on November 17, 2013
Yeah just get the fans to run anyway you can if it dosen't overheat that way and dont worry with the fan system! Wire them up direct to the ignition switch or whatever. After all like you said just to get a few more miles out of it.
of G. T. Service Center on November 16, 2013
Also check the water temp switch on the right hand side of the radiator.
on November 16, 2013
If you mean the water temperature sensor on the bottom right of the radiator. That piece was the first thing I replaced. I replaced it twice because I thought the first one was defective. All the relays and fuses have been tested, they seem ok. If I unplug the sensor the fans run.
of G. T. Service Center on November 16, 2013
OK the radiator fan switch will ground the relay in the J/B 2 on the left side of the engine comp, which also goes through the A/C high pressure switch causing the relay to hold contact open. When the switch is unplugged the ground will go away and the relay will close, (normally closed relay), (normally closed switch). Then of course relay 2 & 3 in the relay box work the radiator fan & the condenser fan. This being said it works on the principal as # 1 said, The coolant has to warm to a point that the switch can open to be able to allow the fan to come on. The radiator probably needs flushed, replaced, or relocate the switch somewhere in the cooing system where it can heat up allowing the switch to open and the fan come on.
on December 13, 2013
I want to thank everyone for their inputs, they all were valid. I was frustrated and had very little time to work on the engine properly. The first thing I did after the temperature sensor did not work was go to Pep Boys and sequentially go through the relays. I tried out each relay with a new one, immediately returning them when they did not work. No success, I tried switching each of the three of them separately. Later, I tested the cooling relays one and two. They were fine. I had no more time so I either drove with the heat or the AC on to keep it cool. Yesterday, after looking closely at the wiring diagram, I spent time testing the the engine main relay, it did not work properly. This one I did not test earlier thinking it was not involved. I did try the new one from Pep Boys that must also have been defective. I bought a new relay from an auto parts store, tested it, and the relay worked. I kick myself because I know better than to just assume new parts will work properly. Take the time to test relays before blindly changing them. Thank you again for your considerate time.
of Gillespie's Auto Service on November 16, 2013
Agree with #1
on February 24, 2014
I was on vacation in January. I just had another look at my Camry. I remembered my first or second car had a similar situation. I repaced the coooling sensor twice and both were no good, so I went to a diferent store to try another one. That one worked, like this Camry. Now the cooling fans work for my Camry. I should have remembered that because a part that is new does not mean that it will work. Thank you all again for your help.
of G. T. Service Center on February 24, 2014
You're right. Good Luck.
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