ST165, what sensor controls fan?

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ST165, what sensor controls fan?

Postby UtahSleeper » Sun Jul 26, 2015 6:00 pm

So, simple question.

Is it the temp sensor at the bottom of the radiator that controls the fan?
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Re: ST165, what sensor controls fan?

Postby zaluss » Sun Jul 26, 2015 6:55 pm

UtahSleeper wrote:So, simple question.

Is it the temp sensor at the bottom of the radiator that controls the fan?


That sensor will determine when to engage the fan depending on the temperature of the coolant. If the sensor is disconnected, the fan will always engage (even with the engine off, ignition set to ON).
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Re: ST165, what sensor controls fan?

Postby Awesome-Trac » Sun Jul 26, 2015 11:02 pm

So a bad sensor will cause the same symptoms correct cause mine stays on with just the ignition on
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Re: ST165, what sensor controls fan?

Postby zaluss » Mon Jul 27, 2015 3:02 am

Awesome-Trac wrote:So a bad sensor will cause the same symptoms correct cause mine stays on with just the ignition on


I believe so as a Toyota fail safe.
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Re: ST165, what sensor controls fan?

Postby underscore » Mon Jul 27, 2015 4:10 am

Yep, bad sensor or broken wire will hold the fan on.
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Re: ST165, what sensor controls fan?

Postby UtahSleeper » Mon Jul 27, 2015 3:23 pm

Thanks, just wanted to verify. My fan stays on and I am about to replace my radiator. Would rather replace the sensor while I am doing this.
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Re: ST165, what sensor controls fan?

Postby UtahSleeper » Mon Aug 10, 2015 2:20 pm

Well, I replaced my sensor and the fan is still on all the time.

I will try and check the wiring, but could it potentially be a relay?
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Re: ST165, what sensor controls fan?

Postby zaluss » Mon Aug 10, 2015 4:32 pm

UtahSleeper wrote:Well, I replaced my sensor and the fan is still on all the time.

I will try and check the wiring, but could it potentially be a relay?


If the AC has been removed from the car, that will trigger the fans to go as well. You'll need to connect a sensor on the firewall (or short it) to stop this from happening.

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Re: ST165, what sensor controls fan?

Postby UtahSleeper » Mon Aug 10, 2015 7:26 pm

I did not know this. Thanks I may try this or just reconnect the wires to the ac compressor and see if it fixes.

I plan on eventually trying to get the 215 compressor hooked into the stock pieces, so I left it installed on the block.

Is shorting it as easy as just jumping the plug with a wire?
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Re: ST165, what sensor controls fan?

Postby RedCelicaTRD » Mon Aug 10, 2015 8:29 pm

Compressor wires shouldn't matter. It's the pressure switch on the a/c lines up by the firewall that you will need to make sure is plugged in.

When I had a fan that was stuck on, it was caused by a broken wire by the fuse box.
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Re: ST165, what sensor controls fan?

Postby UtahSleeper » Tue Aug 11, 2015 1:57 am

RedCelicaTRD wrote:Compressor wires shouldn't matter. It's the pressure switch on the a/c lines up by the firewall that you will need to make sure is plugged in.


Can you just jump the connector or does it need the switch? PO removed all the lines and such, so there is no switch to be had. :/
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Re: ST165, what sensor controls fan?

Postby alltracman78 » Tue Aug 11, 2015 2:28 am

You can jump the connector. That's all the switch does [it disconnects the "jumper" if the pressure is to high].
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Re: ST165, what sensor controls fan?

Postby RedCelicaTRD » Tue Aug 11, 2015 12:36 pm

There is a factory jumper for the ST185 so I assume the ST165 has one also. They have been discontinued, but if you can find a car without A/C in the junkyard it might have the factory jumper still on the harness.
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