AC only works on Max AC setting.. anyone run unti this?

bretthays said:

I got this truck a couple of months ago in the winter and never tried the AC before I installed the 7” Cluster and 8.4 UAQ upgrade, so I don’t know if the problem existed prior to that.

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MRFREEZE57 said:

You need to put a set of gauges on the system to see what is happening.

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crash68 said:

The 8.4 UAQ might be what's causing the problem, you might have to do the ATC mod so the system works correctly.
I bet @Mpgrimm2 would know if this is the situation and he would be the one to talk to about the wiring harnesses needed to do the ATC mod. It's a temperature and humidity sensor that needs to be added then enabled with AlfaOBD.

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bretthays said:

I installed the new hvac module that came with the UAQ. I got it from 4thgenmods. I thought the humid and temperature sensor was only needed for the automatic temperature control? I don't have that.

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crash68 said:

The 8.4 UAQ might be what's causing the problem, you might have to do the ATC mod so the system works correctly.
I bet @Mpgrimm2 would know if this is the situation and he would be the one to talk to about the wiring harnesses needed to do the ATC mod. It's a temperature and humidity sensor that needs to be added then enabled with AlfaOBD.

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Mpgrimm2 said:

Yep. Known issue with the 4c upgrade.

You will need to add the needed ATC hardware. ... Either with my universal add-on set or replace 4th gens 8.4 harness set with mine ... Not much price difference between the 2 options.

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bretthays said:

So I can retain my same bezel and controls or do I have to replace that as well?

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crash68 said:

You don't need to change the bezel, as the Auto button is available on screen. I changed the bezel on mine about a year after I did the ATC mod because I found an inexpensive one in the classified section of the forum. I swapped in an 8.4 UAQ a couple of months before I changed the bezel. It is nice to have the bezel with the Auto button though.

My truck was already had the 7 spd fan. You do need the humidity sensor on the windshield but the dash solar sensor is optional.

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bretthays said:

What does the dash solar sensor do?

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crash68 said:

Doesn't seem to effect operation of the HVAC system, but what's strange is the Dual Climate trucks came with the dual solar sensor where as the truck without came with a single solar sensor that is for the headlights.

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bretthays said:

So I can retain my same bezel and controls or do I have to replace that as well? I couldn't find the universal add-on harness on the web site, I found the sensors and I also found your full 8.4 harness with single zone ATC... unless this is it "ATC Pt2 Humidity Sensor Add-on Harness (7spd Trucks)" but that is only the humidity sensor.

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