Page 1 of 2

2014 GMC Sierra not cooling well

Posted: Tue Jul 07, 2020 7:56 pm
by robmaxfli
Howdy,

As the title states I am not getting nice cold air out of the vents. I measured vent temps and they are almost 70 degrees. On a 93 Degree day here in Texas.
Today I decided to evacuate the system, pull a vacuum that held , and then recharge to the correct amount of 21oz. Vent temps are still @ 70 degrees (85 degrees outside). The Low side pressure is 35 and High side is 192. The AC line going to evaporator is cold to the touch and sweating.
I'm not sure where to go from here and would appreciate any suggestions. :)

Re: 2014 GMC Sierra not cooling well

Posted: Wed Jul 08, 2020 2:08 am
by Dougflas
Have you blocked off the heater core to see if you have a reheat problem? Are the blend doors functioning properly? Leave the refrigeration system alone until you have checked for a reheat from the heater core.

Re: 2014 GMC Sierra not cooling well

Posted: Wed Jul 08, 2020 2:30 pm
by robmaxfli
I'm not familiar with a heater core reheat. But I will bypass the core tonight to see if it improves the AC.
thanks

Re: 2014 GMC Sierra not cooling well

Posted: Wed Jul 08, 2020 5:01 pm
by B52bombardier1
Could also be a blend door "air valve" mixing problem in the dash - heater air mixing with cold air.

Rick

Re: 2014 GMC Sierra not cooling well

Posted: Thu Jul 09, 2020 5:03 am
by Dougflas
reheat means the air flow is going thru the heater core. Easiest thing to do is eliminate the heater core. ( Yes, by-pass it)

Re: 2014 GMC Sierra not cooling well

Posted: Thu Jul 09, 2020 10:36 am
by robmaxfli
just in case this helps anyone, I was able to achieve 43 degrees out the vents after i bypassed the heater core. its 90 degrees outside here. I'm thinking about leaving it this way for the summer :)

Re: 2014 GMC Sierra not cooling well

Posted: Thu Jul 09, 2020 11:08 am
by Dougflas
You might try an internet search on the blend door on the Sierra. Common problem. With the heater by-passed for the summer, your defroster will not work.

Re: 2014 GMC Sierra not cooling well

Posted: Thu Jul 09, 2020 11:33 am
by Al9
AC alone with no reheat still has a demisting effect though. Especially if kept in top shape. Just adjust the blower fan to a lower speed if you feel too cold.

Re: 2014 GMC Sierra not cooling well

Posted: Thu Jul 09, 2020 1:24 pm
by robmaxfli
Dougflas wrote:You might try an internet search on the blend door on the Sierra. Common problem. With the heater by-passed for the summer, your defroster will not work.


I've done lots of searching for blend door on the Sierra and the common problem that people have is for those with dual zone climate. For example "the pass. side is cold but the driver side is warm" or vice-versa. Mine does not have dual zone and is the same temp out of all of the vents. I just reinstalled the heater core hoses and tested again. Nice warm 72 degrees vent temp.
If i rotate the temp knob over from cold to hot it will blow semi-hot out of the vents. Using the heater alone is deep hot.

Re: 2014 GMC Sierra not cooling well

Posted: Thu Jul 09, 2020 1:29 pm
by Al9
robmaxfli wrote:"the pass. side is cold but the driver side is warm"

This is also a typical sign of a seriously starved evaporator.