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
What kind of vehicle are you working on? A VIn number would also be helpful.
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.
I could be over loo It. New site and all.
What type vehicle and year?
O rats sorry guys, I thought I wrote model in somewhere. Guess not, danng. 2011 Toyota sienna
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 scope to see it. I had an 09 Camry that I was able to just buy the flow sensor off ebay, yes I know.. but it was for test purposes for one I was testing at home. The flow sensor was $40 and the new compressor was over $500 from oreilly.
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.
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"
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 second capture shows the data during operation. Notice that when the target temperature is overrun the flow rate decreases (increased voltage value). In complete data you should also see a reduction in command to the displacement solenoid.
The data should look like other feedback systems we are familiar with.