HVAC compressor

Maynard Technician Elmira, Ontario Posted   Latest  
2011 Toyota Sienna LE 3.5L (2GRFE) 6-spd (U660F)—5TDKK3DC7BS110133
A/C Compressor Will Not Engage

With System fully charged compressor will not engage. Lots of reading and tsb suggesting "flow sensor" to be an issue on these platforms, we are intending to replace compressor due to faulty "flow sensor" which is built into compressor. However, I would appreciate some second opinions if I can get them. I cannot engage compressor when commanding on with biodirectional control. Manually supplying power to compressor clutch will engage clutch. Flow sensor reads constant 3.65v, tsb suggests compressor will not be commanded on with anything less than 3.7v. Compared to another van of same year and system, system in idle state flow sensor reads 4.02v and when A/C is running it will drop down to 2.5V.

So my questions, if this flow sensor is keeping compressor permission off due to it being .05 v too low, will this also over ride the biodirectional command from scantool? And the other question to anyone with experience on these. Is this slightly low voltage reason to believe it will not engage compressor?

Further information, we tested for shorts to power and ground in flow sensor harness back to A/C amplifier. Also when flow sensor is unplugged value on scantool goes to 5V. When manually testing harness with sensor unplugged it is observed 2 wires have 5V and 1 ground. I was not able to determine which is 5v supply and which is sensor wire to artificially supply a 4V signal.

Thanks for reading

Albin Diagnostician
Leavenworth, Washington
Albin Default

What kind of vehicle are you working on? A VIn number would also be helpful.

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Scott Manager
Claremont, California
Scott Default

Albin, we’ve edited his post and added the vehicle after he supplied us with the VIN. In the future we plan on making editing possible so we can help folks get the proper in place when seeking advise and or support.

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Joe Technician
Roanoke Rapids, North Carolina
Joe Default

I could be over loo It. New site and all. What type vehicle and year?

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Maynard Technician
Elmira, Ontario
Maynard Update

O rats sorry guys, I thought I wrote model in somewhere. Guess not, danng. 2011 Toyota sienna

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Maynard Technician
Elmira, Ontario
Maynard Default

3.5L Manual A/C

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Craig Technician
White House, Tennessee
Craig Default

I had a 13 Rav4 with the same issue. Showing a 3.50v at idle and the compressor wouldn't come on. I could manually turn it on with the scan tool. If its less than 3.7 the computer thinks that there is already flow and it won't activate the flow sensor. I've had several of these give me issues. The signal to the compressor is ac signal if I'm not mistaken so you will have to monitor it with a

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Maynard Technician
Elmira, Ontario
Maynard Default

Ok thanks Craig, I guess we will see tomorrow if the clutch will actually engage again with the new compressor. From your info i am sure the permission will be granted, I am just curious now yet if there will be some problem in the clutch circuit.

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Maynard Technician
Elmira, Ontario
Maynard Update

One for the record. We installed a new compressor today, (which in turn means new flow sensor) Sensor reads 4.19v with compressor off. And of all things compressor now turns on fine.... flow sensor is at 1V with compressor in operation. I suppose this value will actually be variable in different conditions due to the compressor being variable displacement, and its job is to report "flow"

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Jim Curriculum Developer
Frederick, Maryland
Jim Default

The first capture is the startup of a 2012 Camry that shows this system. It was shut off on the left and the evaporator temperature was climbing. The flow sensor was above 3.75 volts. When the system is commanded on the flow sensor drops to about 1.5 with the regulator control current just over half an amp. As the evaporator cools down and the pressure increases the flow rate is reduced. The

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William Diagnostician
Ashland, Virginia
William Default

Not much in AllData on the flow sensor. Spec says 10kOhms or higher. No voltage specs.

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