Toyota ac flow sensor

Richard Technician New York Posted   Latest  
Unsolved
HVAC
2013 Toyota Sienna LE 3.5L (2GRFE) 6-spd
B1479
No A/C

Car came in with no A/C verified correct charge level still wont work. Next I scan and find history code B1479. Checked voltage at idle no A/C and it reads 3.6v which is out of range. I have one on order to replace but was curious to see if I could get the voltage to change myself took a magnet right near the the sensor and it works fine for the key cycle. Is this a hall effect sensor? Any theories as to why the magnet worked? 

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Rick Diagnostician
Connecticut
Rick
 

Usually the compressor is not compressing the r134 and the sensor is accurate most likely compressor failure they are a bit pricey

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Maynard Technician
Ontario
Maynard
   

The sensor is mounted to the outside of the case, and there is a flow sensor inside on a little track I think…. Therefore the sensor is kind of reading magnetically through the case anyway. So if you are able to disrupt the magnetic field just far enough with an external magnet to get the sensor within range so the module turns on the compressor…. Now the flow sensor inside moves again and…

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Helpful
Jon Owner/Technician
California
Jon
 

These are usually compressor failures or solenoid failures or a combination of the 2.

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Shaya Mobile Technician
New Jersey
Shaya
 

The failure is that rust builds up under the sensor causing gap, therefore reading lower voltage at off/rest point. The a/c amplifier (aka module) won't command a/c on if voltage is not between around 3.75v-4.2v. Placing a magnet will change voltage like any hall effect (aka magnetic sensor). The trick here is to place a magnet with the right amount of strength and in the right spot to raise the…

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Interesting
Richard Technician
New York
Richard
 

It was either this or I was going to us an op amp and a couple resistors 10k and 750 for mine that was reading 3.6v but either way thank you all for explanation

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Gary Diagnostician
New Jersey
Gary
 

If I'm not mistaken, you go into HVAC module. Use your scanner. You should be able to turn the compressor on using bi-directional control. if it works then that verifies what everybody else has said. The internal pressure sensor goes bad. I have seen some of them replaced. In most cases you just replace compressor.

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Timothy Owner/Technician
Wisconsin
Timothy
 

It's not a pressure sensor, just so you know…

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Gilles Technician
Quebec
Gilles
 

Remove the sensor and clean its housing put a very light coat of dieletric grease reinstall tested you will have a data of 4 volts if your sensor is good

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