Gen2 A/C Sensor Troubleshooting guide (help needed)

I would like to have a thread dedicated to troubleshooting the Climate Control sensors on any Gen 2 Volvo VNL/VT/VHD etc.

My truck is a 2008 Volvo VT880

I have 2 Climate Control Units. BEHR C9106 P#20549634 & a MAHLE R2659007 P#21326144

Both of these units seem to be functioning identically so I don't think its the Climate Control Module that is the issue.

I'll update this post so hopefully in the future when people troubleshot a/c issues they can come here to get a basic breakdown and some basic steps to rule out sensors.

I work best with pictures, below I'll post a diagram I did to map out the pins on the back of the Climate Control Module.
I have questions about some of them which are in the photo.

Also linking a picture of the two wiring diagrams I was able to locate for the Climate Control.

If you can answer any of the questions please do so I can update my picture with good info on each pin.

My hope is to be able to use a multimeter right in those pins to test sensors or detect other potential issues, but I need to know what each pin does or what it should be reading when the truck is not running and the ignition is on.





Some things I have tried is to see if I could get continuity between the wire going into the Climate Control Module and the one going into the sensor, I could only get the A/C clutch positive to show a direct connection to the CCM.

As always, any help is appreciated. I'm doing this thread because I've searched high and low of existing threads and nobody seems to have a good all around thread on this.

 

Helped greatly Snail.
A few things I immediately gleaned was with the sensor ranges.

GB6 must be the low side sensor, it reads resistance by looking at the return voltage - specifications indicate the voltage has to be between .8v to 4.5v.

Evap sensor is the same, return voltage cannot exceed 3.1v for GB19 - doesn't really say how many ohms of resistance one could expect from the sensor at room temperature to make checking it with a multi meter easy.

One thing I did not see is what is the exact voltage and amperage the Control Unit sends to the sensors, I have a testing station I could mimic those inputs, apply them to the sensor and measure return voltage. I know it sends 5v but at what rate?

 

not getting a signal to the compressor to turn on from the Control Unit. Figure its a sensor. Its always something, I've had horrible luck with A/C so its just a matter of time before something else goes wrong.

Should probably go ahead and buy a automatic recovery and charge machine at this point.