2011 Tahoe AC Cuts Out

[Jon Miles]

I am turning to the experts here because I'm banging my head against the wall with the ac system in the truck.
Some backstory:
Had an ac leak at the rear evaporator (no surprise with the age of the truck).
Replaced the rear lines and evaporator = leak gone.
Had the system recharged to spec'd pressures - still no leak.
Replaced the high pressure sensor, ac compressor relay, ambient temp sensor and the evap temp sensor.
Intermittent cooling persisted so I pulled the relay and jumped it. Compressor comes on and stays on so I replaced the relay.
AC runs cold for 15 mins or so after start up and then goes warm. Occasionally, it will come back on but it didn't seem to have method to its madness.
Until I noticed that when the volts drop off to 12~ at highway speeds, that is when the ac compressor kicks off and the air goes to ambient temp from the vents.

My troubleshooting mind points me to the compressor clutch but I really wanted to see what you all thought...

Thanks in advance.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally help you with your question; however, other members on this Forum that are much more knowledgeable than me in this area will chime in.

 

[j91z28d1]

is it an automatic ac or a manual?

it's hard to do anything with a automatic ac without a good scanner you can see the ac request from the ecm

 

[swathdiver]

I am turning to the experts here because I'm banging my head against the wall with the ac system in the truck.
Some backstory:
Had an ac leak at the rear evaporator (no surprise with the age of the truck).
Replaced the rear lines and evaporator = leak gone.
Had the system recharged to spec'd pressures - still no leak.
Replaced the high pressure sensor, ac compressor relay, ambient temp sensor and the evap temp sensor.
Intermittent cooling persisted so I pulled the relay and jumped it. Compressor comes on and stays on so I replaced the relay.
AC runs cold for 15 mins or so after start up and then goes warm. Occasionally, it will come back on but it didn't seem to have method to its madness.
Until I noticed that when the volts drop off to 12~ at highway speeds, that is when the ac compressor kicks off and the air goes to ambient temp from the vents.

My troubleshooting mind points me to the compressor clutch but I really wanted to see what you all thought...

Thanks in advance.

Welcome to the forum Jon. Do you know anyone with a bi-directional scan tool like a Snap-On or Tech-2? They can see any internal trouble codes for this and or the reasons why the compressor kicks off and a lot of other things for diagnosis. We have a Tech-2 owner's map where you can see if anyone on here lives near you that has one.

@91RS @rockola1971

 

[mikez71]

Intermittent cooling persisted so I pulled the relay and jumped it. Compressor comes on and stays on so I replaced the relay.
AC runs cold for 15 mins or so after start up and then goes warm. Occasionally, it will come back on but it didn't seem to have method to its madness.
Until I noticed that when the volts drop off to 12~ at highway speeds, that is when the ac compressor kicks off and the air goes to ambient temp from the vents.

Does the A/C kick off with relay jumped at highway speed (voltage)?

There is a setting in hptuners "airflow system minimum voltage" which happens to be set at 12.0 volts...

 

[OR VietVet]

"Until I noticed that when the volts drop off to 12~ at highway speeds, that is when the ac compressor kicks off and the air goes to ambient temp from the vents.

My troubleshooting mind points me to the compressor clutch but I really wanted to see what you all thought..."

Voltage drops to 12 volts where? The clutch needs correct voltage to work and if is loosing that voltage, then the clutch will not engage and if you replace the clutch, you still have the voltage problem. What are the pressures in the system when it is working? System may be freezing up. I am unsure that all your info is complete. Not accusing, just stating uncertainty. Why did you not replace the orifice and the accumulator? How long on the vacuum pump?

 

[Jon Miles]

is it an automatic ac or a manual?

it's hard to do anything with a automatic ac without a good scanner you can see the ac request from the ecm

j9 - It's an auto ac system but I hardly use the feature, just run it manual.
Agreed - A buddy has a Snap-On scanner. I'll try and hook up with him later this week.

 

[Jon Miles]

Does the A/C kick off with relay jumped at highway speed (voltage)?

There is a setting in hptuners "airflow system minimum voltage" which happens to be set at 12.0 volts...

Mike, the short answer is no, it does not cut out. Did exactly that last week when it was 90 degrees. 45 mins into an hour drive, the airflow through the vents slowed down drastically. Pulled over, popped the hood and the dryer was frosted over. Pulled the jumper wire and replaced the relay. Airflow improved and the air was frigid from the vents.

 

[Jon Miles]

"Until I noticed that when the volts drop off to 12~ at highway speeds, that is when the ac compressor kicks off and the air goes to ambient temp from the vents.

My troubleshooting mind points me to the compressor clutch but I really wanted to see what you all thought..."

Voltage drops to 12 volts where? The clutch needs correct voltage to work and if is loosing that voltage, then the clutch will not engage and if you replace the clutch, you still have the voltage problem. What are the pressures in the system when it is working? System may be freezing up. I am unsure that all your info is complete. Not accusing, just stating uncertainty. Why did you not replace the orifice and the accumulator? How long on the vacuum pump?

OR - Sorry for the lack of info and appreciate you chiming in...At the volt gauge on the dash, I did not put a volt meter to the compressor as yet. When functioning, the low is 35psi +/- and the high is 175-190.
I had the system evacuated before I replaced the rear lines and evaporator. I did replace the orifice tube at that time - forgot to mention that replacement. Left the accumulator alone.
When I took it back to be refilled, it was on the vacuum for about an hour.

 

[Jon Miles]

Welcome to the forum Jon. Do you know anyone with a bi-directional scan tool like a Snap-On or Tech-2? They can see any internal trouble codes for this and or the reasons why the compressor kicks off and a lot of other things for diagnosis. We have a Tech-2 owner's map where you can see if anyone on here lives near you that has one.

@91RS @rockola1971

Thanks Swath.
I've been lurking for awhile but this is my first post...the amount of knowledge here is impressive and I value that greatly!
Yes, a friend has a Snap-On scan tool. Hoping to get over to see him in the next few days.