NO AC and all temps read negative 39 or 40 degrees

[David Hartsoe]

Dealership says compressor is bad and wants 1400$ to replace it. Snapon scan tool says all HVAC readings are negative 39 or negative 40 degrees. 

 

I suspect there is an HVAC control module that needs replaced but need help diagnosing. 

[Bash74]

If your scan tool isn't detecting a bad module then there probably isn't one or your scan tool doesn't have that capability. If that's the case try and get access to one that can access the modules..

[CrawlSlow]

When adjusting to heat, do you get heat? Does the circulation/fresh air work? When adjust fan speed from low to max, does it make a difference? If all these works then it's your AC system having issue. Troubleshoot your AC system.

[David Hartsoe]

Windshield temp says 32 degrees when it's 85 outside. Shows interior duct temperatures of -40 degrees. It gets cool in the truck but not cold. Heat works fantastic. It's dual zone the.p if it matters. 

 

Head pressure looks to be correct. Line going into firewall is cold and dripping. Compressor kicks on just fine. 

[CrawlSlow]

Sounds like your compressor is working okay. Have you measure the temp at the vent to see what temp you get coming out? 

 

Also is the passenger temp in sync with the driver side?

[David Hartsoe]

Temp coming out the vent is in the 60's, scan tool says reading out of some of the vents is negative 40 degrees. 

 

[CrawlSlow]

Check your AC pressure on both high and low side?

[Ianf]

Sounds like a temp sensor is faulty somewhere. i.e. ambient temp sensor.

 

[rlcole321]

Sound's like a sensor problem, may have to purchase a detailed schematic of the auto-air system to see how many sensors there are and locate them and test them individually.