AC grinding/hiss and Warm Air

[MrBalll]

As of a few days my cold air is done for.
When the AC is on every five or so seconds I hear a hiss near passenger floorboard as well as a grinding noise outside. Both noises happen at the same time.

I'm not sure that it's the actuator inside as I never change the temp from what it is set to. I'm sure it's on it's way out as I do hear it grind occasionally.


With the hissing noise does it mean both a leak and a possible bad compressor?



Inside noise starts around 10 seconds. Turn volume up to hear.

Exterior noise is loud enough and there is fan noise, but grinding noise is obvious.

 

[Doubeleive]

that's not really a grinding noise that is the clutch on the ac pump trying to engage the system but likely there is no Freon so its not engaging and shutting back off, I would guess there has been a leak in the system somewhere. I would advise having the a/c system looked at by a shop

 

[MrBalll]

So I went out and bought one of the cheap little ac recharge cans with a gauge and I put a little bit into the system. The gauge shows the system to have 43 psi on the low so that's good.

I checked the air inside and it's coming out about 100 degrees full blast. I noticed the clutch is engaged with no issues starting or stopping when AC is turned on or off. Low line is cool and high is hot.

When I turned on heat it came out at about 120 before I cut it off and it went back down to 100 degrees with AC on.

When I turn it to floor, combo or face I can hear the door moving and the air changes to it's position with no issues.



What is the next thing in line to check at home?

 

[SnowDrifter]

43 psi with ac on or off? High or low side? What does the gauge show when your compressor engages?

 

[MrBalll]

Pressure is 43 with the AC on at the low side.
The gauge showed 100 F with the compressor running. Outside temp was around 95.

The low side line is cold to touch and the high side was hot to the touch so I would guess the compressor is circulating the refrigerant.

 

[MrBalll]

Is there an actuator that cycles between hot and cold I can look at?

 

[SnowDrifter]

Yes but I don't remember the location. There's a hot/cold blend door

 

[MrBalll]

So I tried the HVAC control reset with removing the fuse and all that and it did nothing. I do get colder air in the rear now, but not cold. Front air is still coming out at about 80 degrees on driver and passenger side.

There are way too many blend doors, but I'm wondering if I found the right one. I have the automatic climate control system in my Tahoe.

Would this be the right door?
https://www.summitracing.com/parts/fss-73004

 

[retiredsparky]

You are following a logical path to troubleshoot this. It sounds like you have the dual temp controls for driver and passenger, so there is a blend door for each side. It is possible for both blend door actuators to fail at the same time if there is a failure in the control panel on the dash. The commands for the blend door positions are separate outputs from the controller that vary based on temperature sensors in the duct work. The compressor turns on and off as needed to maintain a certain range of pressures and temperatures in the system.

One disadvantage of an automatic system is that engineers keep adding sensors, actuators and software until they get all the problems solved in the factory. It only takes one failure to mess up the system. There are some independent shops that know quite a bit about these GM systems, because GM seems to have the same list of failures in many of these rigs.

 

[MrBalll]

Going to bump this back up.

Does anyone have a master list of what actuator goes where? From what i can find there are several actuators for the front and rear. I believe my front temp control actuator is bad, but I don't want to order the wrong one and waist too much money. Curious if anyone has a part number reference I'd appreciate it.