2014 Versa - AC inop
Old AC compressor locked up and threw the belt. Installed new compressor and belt.
When I press the AC button, I can hear the AC compressor engage. It is a momentary button, when I release it, the ac compressor shuts down. Gauges show the compressor is functioning when I do this. If I hold the button, it stays on. The LED on the button never illuminates.
I cross checked the pressure sensor value to the gauges, using a chart that I found in SI. THe pressures are correct.
I then put the pico on the Thermo Amplifier. Yellow and black give me power and ground…Orange is the signal. Last week I had a very erratic, lets call it noise, on this signal…So I ordered one from Nissan and installed it today. AC still inop. Now the scope shows 0v on the signal wire, orange. Unplugged, this orange wire shows a steady B+ voltage. As soon as I plug it in, it goes down to 0v.
SI is kind of ambiguous about this sensor. One page says at one temp this amplifier will open the circuit, another page says this amplifier should produce a 12v square wave about every 10ms. What is the correct function of this part?
LiveData shows the switch being pressed, but it won't stay on. I suspect it has a bad BCM, but no concrete proof. LiveData shows correct pressure pids.
This system is kind of funky because the way the compressor gets controlled: Control head --→Thermo Amp--→BCM--→Pressur Sensor--→ECM--→Compressor Relay--→Compressor
Anybody have any ideas on why this won't stay powered up?
Sounds like you need a/c control head. If it will work when holding the button in.
THat was my thought too, but this is a momentary button. There is not latching mechanism. Also, the LED on this button is lit directly by the BCM, not the control head. That makes me think for 1 reason or another, the BCM does not want the AC on.
does the system have a evap temp sensor? If you read the description of operation it states that the front control is what submits the request to the bcm, bcm sends request to pcm , pcm sends request to ipdm e/r. ipdm e/r turns on the relay. temp sensor could cancel it out if in defauly
Yes I tested the evap temp sensor. Nissan calls it a Thermo Amplifier.
Sounds like the button latch is bad from being pushed to had too many times.
My bad it is a momentary button, that leads to the BCM not completing the command. Look at all the reporting devices for an anomaly such as an evap temp sensor reading -?? degrees or a sun load sensor way off. There is something inhibiting the initial command to operate.
The evap temp sensor is what Nissan calls a Thermo Amplifier. Some of SI says it's is an open/closed switch, some of SI says it outputs a PWM to the BCM. Old, and new output 0V flat line on the scope.