Intermittent A/C?

[jrobie79]

So I have a strange problem with my AC that I've never really experienced with any other cases l vehicles before. 2011 Escalade and the AC works intermittently. Typically when I first start my truck up in the morning the AC works fine, blows cold air like I've been used to for the past 5 years, however after about 10-20 minutes it just stops blowing cold air, it's not quite ambient temperature but it's nowhere cold enough to keep me cool. If I shut the car off and run into a store or something, it repeats this behavior, but the cold doesn't last as long this time.

Would this happen if it was low on refrigerant? My other cars wouldn't get cold at all onelce the refrigerant got below whatever minimum threshold it needed ll to be at, never intermittently. Obviously if it's low there's a leak somewhere, so before I open the system, and have to replace the drier/fix the leak/vacuum it out, I was wondering if it might be a sensor or switch that triggers the compressor? Could the compressor clutch be the issue, that once everything warms up and expands it no longer works as it should?

Thanks

 

[Doubeleive]

I would check the inside ambient air temperature sensor's and blend door actuator before proceeding to messing with the ac pump
there is one sensor right above the driver's head in the headliner being yours is a escalade you will see 2 little speaker looking things, one is the temp sensor, the other is the bose anc mic, then in the rear passenger headliner will be the 2nd temp sensor. the hot/cold blend door is under the glove box panel closest to the blower motor.

if the temp sensor is going goofy it could be giving a false reading and adjusting the temp on it's own.

if you reach back and feel the rear ac with your hand and compare it to front and if the rear is still cold then it's a good bet the sensor is going out or the blend actuator is or both. the sensor over you head is for the front the one in the rear passenger side is for the rear.

 

[jrobie79]

Is there a diagnostic procedure to verify correct operation of the blend door? Or any pin resistance values to ohm out the temp sensor?

I would check the inside ambient air temperature sensor's and blend door actuator before proceeding to messing with the ac pump
there is one sensor right above the driver's head in the headliner being yours is a escalade you will see 2 little speaker looking things, one is the temp sensor, the other is the bose anc mic, then in the rear passenger headliner will be the 2nd temp sensor. the hot/cold blend door is under the glove box panel closest to the blower motor.

if the temp sensor is going goofy it could be giving a false reading and adjusting the temp on it's own.

if you reach back and feel the rear ac with your hand and compare it to front and if the rear is still cold then it's a good bet the sensor is going out or the blend actuator is or both. the sensor over you head is for the front the one in the rear passenger side is for the rear.

 

[Doubeleive]

Is there a diagnostic procedure to verify correct operation of the blend door? Or any pin resistance values to ohm out the temp sensor?

@PNW VietVet or @swathdiver may have the temperature sensor diagnostic ohm's
correct troubleshooting would require a tool like the tech2 to verify blendoor operation and the desired-vs-actual temperatures
the ambient sensor's are only around $25 online and easy to replace
without a tech2 it's probably easier to manually check as I suggested with your hand or a thermometer front-vs-rear temps that's a dead giveaway if the front gets warmer and the rear stays cooler.
you can visually watch the blend door under the glove box and if you see it moving on it's own towards warm then that is also a giveaway that the temp sensor is not operating properly, if the blend door does not move at all and you still get warm air then you may have other ac pump issue's

**one thing to note is the purpose of the ambient air sensor is to keep the temp at the desired temperature so the blend door moving without you adjusting anything could be normal but not if it is obviously way off.

 

[gooffeyguy]

May also be the coil (or something) freezing up.

My 2001 with manual hvac controls will start blowing ambient air after about two hours when on road trips. After stopping to get gas or eat there would be a big puddle of water under it and the AC blows cold again.

Sent from my SM-G930V using Tapatalk

 

[jrobie79]

I have a tech 2, I'll do a little research on that, thanks a ton!

@PNW VietVet or @swathdiver may have the temperature sensor diagnostic ohm's
correct troubleshooting would require a tool like the tech2 to verify blendoor operation and the desired-vs-actual temperatures
the ambient sensor's are only around $25 online and easy to replace
without a tech2 it's probably easier to manually check as I suggested with your hand or a thermometer front-vs-rear temps that's a dead giveaway if the front gets warmer and the rear stays cooler.

 

[Doubeleive]

use your tech2 and scan for any BCM code's if there is a error detected it will show on the tech2 and will point you right to the problem (just do a full module scan)
you will be looking for things like feedback error codes.

 

[drakon543]

I've experienced a slightly similar problem when a vehicle just needed a proper recharge also. if you have never had the system charged before its 10 years old. you will periodically lose some refrigerant over the years. typically with a system with a leak you will lose it much faster so it will just work or not work. a system that just needs to be recharged can be sitting right at the minimum so after a few minutes of operation the pressure can fluctuate with the pump cycling and will trigger the low level sensor and it wont reset until the vehicle is shut off and restarted. a short run in and out of the store will still have part of the system charged so it will stop working faster.

 

[swathdiver]

So I have a strange problem with my AC that I've never really experienced with any other cases l vehicles before. 2011 Escalade and the AC works intermittently. Typically when I first start my truck up in the morning the AC works fine, blows cold air like I've been used to for the past 5 years, however after about 10-20 minutes it just stops blowing cold air, it's not quite ambient temperature but it's nowhere cold enough to keep me cool. If I shut the car off and run into a store or something, it repeats this behavior, but the cold doesn't last as long this time.

Would this happen if it was low on refrigerant? My other cars wouldn't get cold at all onelce the refrigerant got below whatever minimum threshold it needed ll to be at, never intermittently. Obviously if it's low there's a leak somewhere, so before I open the system, and have to replace the drier/fix the leak/vacuum it out, I was wondering if it might be a sensor or switch that triggers the compressor? Could the compressor clutch be the issue, that once everything warms up and expands it no longer works as it should?

Thanks

It's probably low on refrigerant. Using your Tech-2, you can pull up the pressure on the engine side and compare it with a chart to see if it's within spec. In the BCM area, you can change the temps and manually control the actuators and of course check their counts, desired versus actual, same for the temps. Always pull the codes first.

To check clutch operation, simply see if it's engaged or not. You can hear it click on and off and look down into the engine bay to verify the same.

 

[Trippers99hoe]

My new to me Tahoe acted just like this ,it was the evaporator temp sensor.
The dealership put it on a Tech 2 to diagnose and I replaced the sensor at home.

They said the evap temp sensor was stuck t 24deg and was telling the A/C system it was to cold.
The sensor was $15.87 GM GENUINE 1551267 @Rock auto

 

[jrobie79]

They said the evap temp sensor was stuck t 24deg and was telling the A/C system it was to cold.
The sensor was $15.87 GM GENUINE 1551267 @Rock auto

Where is that sensor installed? I know theres a pressure sensor on the high pressure like in the engine bay

 

[Trippers99hoe]

Mounted to evaporator core ,the wire for it comes out of heater a/c box behind the glovebox directly below the passenger air bag


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[jrobie79]

Great thanks, I wish I knew how to use my tech2 to it's full capabilities to help with this. There's no codes, but I couldn't seem to find out what that sensor or the pressure sensor were giving for readings

 

[Trippers99hoe]

I don't have a tech 2,but somewhere in there you can see all the temps.
I bet somebody here will help you through it.

 

[Foggy]

If your temps etc are reading "normal" ... then it could just be an old fashioned
mechanical issue.
Make sure your electric fans are kicking ON
Check to make sure you don't have any debris like a plastic bag covering the condensor/radiator areas
Make sure your AC belt isn't vibrating/flopping/worn: it is a "stretch to fit" belt and
can be worn out without any normal signs

 

[rockola1971]

May also be the coil (or something) freezing up.

My 2001 with manual hvac controls will start blowing ambient air after about two hours when on road trips. After stopping to get gas or eat there would be a big puddle of water under it and the AC blows cold again.

Sent from my SM-G930V using Tapatalk

Evaporator Coil freezing up is a symptom of a problem, not the problem. The cause is low refrigerant or severely restricted airflow across evaporator coil. Low refrigerant and low airflow causes coil to get below 32 deg and humidity in vehicle freezes on contact which is your ice buildup. Shutoff a/c and it starts melting. This applies to all A/C and Refrigeration systems, especially your central air at home. Keep those filters changed out as needed at home!

 

[gooffeyguy]

Evaporator Coil freezing up is a symptom of a problem, not the problem. The cause is low refrigerant or severely restricted airflow across evaporator coil. Low refrigerant and low airflow causes coil to get below 32 deg and humidity in vehicle freezes on contact which is your ice buildup. Shutoff a/c and it starts melting. This applies to all A/C and Refrigeration systems, especially your central air at home. Keep those filters changed out as needed at home!

It's fully charged, so not sure what exactly the problem is with it. But like I said, it takes a while for it to do it, like when on a road trip and you've been driving for a couple hours with the AC on.

A few years ago my home AC coil would freeze up due to a bad txv valve.

 

[rockola1971]

It's fully charged, so not sure what exactly the problem is with it. But like I said, it takes a while for it to do it, like when on a road trip and you've been driving for a couple hours with the AC on.

A few years ago my home AC coil would freeze up due to a bad txv valve.

A bad Epansion (TXV) valve could cause your problems also. Yours should be located behind the evaporator coil near the firewall. A total blast to get to.

 

[LRD_V8R]

Check refrigerant pressures first. This is a common symptom of low refrigerant. As the system runs, the low side pressure will drop during certain events (like hitting the gas). If it gets too low (typically around 20-25 PSI), it will cut off the compressor until the pressure climbs back up to the minimum threshold to turn on (either in the 40 or 50 PSI range). I prefer to check this using actual gauges and then working from there. If you have a tech 2, you can compare what the PCM is seeing to what the gauges actually read. this can tell you quickly if one of the sensors is failing.

Then there are more insane scenarios where the contacts in the connector from the wiring harness to the compressor connector are corroded, causing intermittent cycling of the compressor. That one took a minute to solve.

 

[Foggy]

My 94 step side has this issue too for the last several years.. I've replaced every component except
the evap core - the entire dash has to be removed and still bust up the air box too ...
So when the airflow thru the vents starts to decline and not be so cold, I just turn off the compressor but keep the system on for a couple of miles. Then air starts to flow better
and I turn back on the compressor and get cold again for period of time.
Remember in these years of GM, if you have it on Max/Recirculate (which you should once cooled down)
the compressor will still run even though the AC light is turned off

I just live with it since my 94 is my toy now. I'm sure the evap core is full of 28 years of
shit so it freezes up easily