2018 Suburban AC Intermittently goes hot

Keith Elliston · August 23, 2021

For last 6 mos our suburban will just start blowing hot (~116 degrees) air like the heat is on. Then it will fix itself. Sometimes it will work for weeks at a time and other times switches every time you start it. There’s no leak, and I’ve had some success recalibrating the actuator (pulling fuse). It always fails after turning car off. Ie, we’re never driving with cold air and it just starts blowing hot.

The problem is not isolated to just driver, passenger, front or rear. Either the whole system works perfectly or it blows hot out of every vent. Any ideas what I’m dealing with?

swathdiver · August 23, 2021

2 hours ago, Keith Elliston said:

For last 6 mos our suburban will just start blowing hot (~116 degrees) air like the heat is on. Then it will fix itself. Sometimes it will work for weeks at a time and other times switches every time you start it. There’s no leak, and I’ve had some success recalibrating the actuator (pulling fuse). It always fails after turning car off. Ie, we’re never driving with cold air and it just starts blowing hot.

The problem is not isolated to just driver, passenger, front or rear. Either the whole system works perfectly or it blows hot out of every vent. Any ideas what I’m dealing with?

Low refrigerant. Take it in and have it checked for a leak and if found, fix it, if none is found, they will re-charge to the proper amount. You can do this yourself with a sniffer, vacuum pump and set of gauges.

If you like to diagnose and or fix things yourself, get the MDI with GDS software so you can talk to all of the computer on board the truck. A VXDIAG NANO or something similar will work as well.

Keith Elliston · August 24, 2021

Thx for response but I don’t think that’s accurate. Low refrigerant would start blowing hot and never come back. When AC works it’s perfect. When it’s not, it’s so hot it’s like the heater is on.

swathdiver · August 24, 2021

2 hours ago, Keith Elliston said:

Thx for response but I don’t think that’s accurate. Low refrigerant would start blowing hot and never come back. When AC works it’s perfect. When it’s not, it’s so hot it’s like the heater is on.

Well, it happened to me and that was the fix. To each his own.

KyleMegg · June 25, 2022

On 8/22/2021 at 8:40 PM, Keith Elliston said:

For last 6 mos our suburban will just start blowing hot (~116 degrees) air like the heat is on. Then it will fix itself. Sometimes it will work for weeks at a time and other times switches every time you start it. There’s no leak, and I’ve had some success recalibrating the actuator (pulling fuse). It always fails after turning car off. Ie, we’re never driving with cold air and it just starts blowing hot.

The problem is not isolated to just driver, passenger, front or rear. Either the whole system works perfectly or it blows hot out of every vent. Any ideas what I’m dealing with?

Hey did you ever find out what the problem was with yourt AC ???

The Zip · June 27, 2022

On 6/25/2022 at 12:55 PM, KyleMegg said:

Hey did you ever find out what the problem was with yourt AC ???

This is not a common problem but it happened to me back in 2014. I made a post about, you'll have to look it up. When outside temps rose to 90+, my AC started blowing hot air from all vents. When temps dropped below 90, the AC worked fine. The 90 degree outside temp is a close guestimate plus or minus 5. The dealer diagnosed the problem to be a faulty "AC High Temp Sensor". Replaced the sensor in 2014 and never had the problem again. Now I have to add that temps where I live barely get to 70 year round so if the problem was not fixed I would probably not know day to day. However, I do frequent areas that regularly get in the high 90s or triple digits. I'll be in LA in a couple of days, weather is scheduled for triple digits. Shoot another post and I'll let you know how it went.