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Radiator fan isn't working the way it's supposed to

Tiny
GEORGEOMAR
  • MEMBER
  • 1997 TOYOTA RAV4
  • 142,000 MILES
Radiator fan isn't working the way it's supposed to. I dismantled the compressor, the condenser, and the ac lines. I replaced the alternator belt with a new shorter belt, and car starts and runs. I saved the electrical connector of the R-134 bottle because: When this connector is unplugged from the circuit, the radiator fan, and the condenser fan turn on and stay on when engine is started. But when this R-134 connector is unplugged from the circuit, the fan(s) never turn on. My next step: I took out the fan #3 relay ( this relay is definitely required if the ac system is to be functioning), and nothing changed. I have a hunch that a jumper wire somewhere at the relay box may be all that's needed to remedy the problem. Thanks for your help. If it makes it easier for you to give me instructions, I have access to Alldata. Com for the rav4.
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Wednesday, March 27th, 2013 AT 6:01 AM

15 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
The fan control for cooling system is controlled by the sensor in the bottom of the radiator.

Removing the ac components will not effect the operation of the cooling fan

Roy
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
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You must be saying the ECT switch or sensor? That crossed my mind. But the R134 bottle electrical plug would still have to be connected to rest of circuit ( even if seperated from the bottle (which is my situation)) to keep the fans from being on continually. Are you saying to keep that in the circuit, but replacing the ECT switch would turn fans when temperature reaches 93†Celsius?
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
ASEMASTER6371
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The switch would operate the fans when temp is needed.

Why dont you just remove the switches from the ac lines and plug them in and tie them off

Roy
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
You need to use a jumper across the A/C pressure switch terminals for the system to work correctly.
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
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Could I access the A/C pressure switch from the big ekectrical plug that used to connect to the compressor?
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
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To KHLow2008
I'm not near my car now, but I think I know where the A/C pressure switch is: It's, if I'm not mistaken, accessible from the electrical connector that connects to the R-134 bottle. I'll verify when I get home
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
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  • 15 POSTS
Good morning,
I put a jumper wire across 2 terminals in place of the R134 bottle, this would bypass the A/C pressure switch if I read the schematic correctly: the bypass stops the fans from being turned on continually. But the fans never turn on as well. Does that mean the ECT sensor went bad. ECT sensor is supposed to make fan turn on when temperature reaches 93celcius?
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
KHLOW2008
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Not the ECT. It is the A/C water temperature switch, item # 12 in diagram.

The fan comes on only when the coolant in radiator is hot ehough to turn it on. When starting from cold, it might take between 20 to 45 minutes before the fan starts working, depending on weather?

Is the engine overheating while the fans are not working?
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
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My mistake. But that's the part I was referring to. It's located at the bottom of radiator, next to the lower radiator hose. Is this part still working? Can it be tested? The reason I thought, either the a/c water temperature switch went bad or the circuit requires another bypass, was because the fan used to turn on when the RPM was raised at idle ( before dismantling a/c components).
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
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The engine is not overheating. ( I forgot to answer you Q. In my previous post).
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
KHLOW2008
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Unplugging the fan switch should turn the fan on.

Raising the rpm does not make the fans turn on. Only when temperature of the coolant at bottom of radiator is sufficient to turn the switch off to break the circuit does the the fan starts to work.

If you don't have overheating issues, I don't think there is a problem with th fan circuit. Let the engine run for a longer period of time and if the temperature does not increase to more than 1/2 on gauge, the fan should come on after some time.
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
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Thank you KHLow2008
The fans are switching on! I put in a new A/C water temperature sensor at the lower part of the radiator. I drove the car, then let it idle, and finally the fans turned on for short periods of time. When I tried the same procedure with the old sensor, the fans would always be off. My conclusion is the the old sensor was a "lazy sensor".

Thank you for your advice.
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
KHLOW2008
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You'rer welcome.

Glad to know the problem has been fixed.
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
KENNAD
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Thanks guys this fixed my problem temporarily until I can install a new switch also. Trying to get 500,000 miles before I trade it in.
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Wednesday, May 5th, 2021 AT 9:51 AM
Tiny
KHLOW2008
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You're welcome.
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Wednesday, May 5th, 2021 AT 9:51 AM

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