AC Light Blinking 3x, then nothing

[MarshMarlowe]

2012 Tahoe LS 2WD 98k miles

I know this has probably already been discussed before. I did some searching, and it's a lot to go thru, so I figured I'd try my luck with a new thread

Wife drove the kid to school this morning in 31 degree F air, and tells me the heater isn't working, her driver's side vent was blowing cold, others were blowing hot, and the windshield won't defrost. I went out to check the truck when she returned, and this is what I found -

-The windshield was defrosted. A small portion was not 'defogged"
-All vents were blowing warm
-I can switch between passenger vents and defrost vents, and everything works, and blows air like it should
-The compressor (snowflake) light blinks 3x, then nothing happens

This is not an auto system, it's the basic dual zone with knobs and wheels, all to be manually selected

I tried the manual reset of the system, by holding the snowflake button and the recirc button simultaneously. This did something, but I'm not sure what it really accomplished. The snowflake light will now stay illuminated, but the compressor only kicks on momentarily, then stops, then kicks on for a brief moment, then stops. It continues like this. The compressor doesn't stay on

Background info - the AC was not blowing cold in the summer. We took it to a shop for diagnosis, they found the freon level to be low. The vac'd it and recharged it, and it worked fine for months. They added dye to the system in case it (inevitably) leaks out again

I hear that common leak points are the schraeder valves, and the rear AC unit lines....

Can anyone help me to know where these points are on the compressor / AC system? Will I need to pull the interior panel in cargo bay to assess the rear lines?

Thank you!

 

[Geotrash]

2012 Tahoe LS 2WD 98k miles

I know this has probably already been discussed before. I did some searching, and it's a lot to go thru, so I figured I'd try my luck with a new thread

Wife drove the kid to school this morning in 31 degree F air, and tells me the heater isn't working, her driver's side vent was blowing cold, others were blowing hot, and the windshield won't defrost. I went out to check the truck when she returned, and this is what I found -

-The windshield was defrosted. A small portion was not 'defogged"
-All vents were blowing warm
-I can switch between passenger vents and defrost vents, and everything works, and blows air like it should
-The compressor (snowflake) light blinks 3x, then nothing happens

This is not an auto system, it's the basic dual zone with knobs and wheels, all to be manually selected

I tried the manual reset of the system, by holding the snowflake button and the recirc button simultaneously. This did something, but I'm not sure what it really accomplished. The snowflake light will now stay illuminated, but the compressor only kicks on momentarily, then stops, then kicks on for a brief moment, then stops. It continues like this. The compressor doesn't stay on

Background info - the AC was not blowing cold in the summer. We took it to a shop for diagnosis, they found the freon level to be low. The vac'd it and recharged it, and it worked fine for months. They added dye to the system in case it (inevitably) leaks out again

I hear that common leak points are the schraeder valves, and the rear AC unit lines....

Can anyone help me to know where these points are on the compressor / AC system? Will I need to pull the interior panel in cargo bay to assess the rear lines?

Thank you!

The AC compressor won't engage below 43ºF ambient temp anyway, so the behavior you initially described is normal for 31ºF outside. I wouldn't do anything with the system until it warms up and you can check it for proper operation.

To answer your question though, the Schrader valves are located on and near the accumulator (large aluminum cylinder mounted to the pax side of the firewall). The low pressure Schrader valve is on the accumulator itself and the high pressure one is located on the large line a few inches from the accumulator. The system needs to be properly evacuated and the r134a recovered before you change them, so it's best left to a shop if/when that time comes.

The rear A/C lines enter the passenger compartment just ahead of the pax side rear wheel and there is an evaporator unit and fan back there. I wouldn't suspect those just yet either.

While you wait for warmer temps, check the coolant level in the recovery tank in the engine compartment. If it's low, it will cause the heat to be sporadic.

 

[MarshMarlowe]

The AC compressor won't engage below 43ºF ambient temp anyway, so the behavior you initially described is normal for 31ºF outside. I wouldn't do anything with the system until it warms up and you can check it for proper operation.

To answer your question though, the Schrader valves are located on and near the accumulator (large aluminum cylinder mounted to the pax side of the firewall). The low pressure Schrader valve is on the accumulator itself and the high pressure one is located on the large line a few inches from the accumulator. The system needs to be properly evacuated and the r134a recovered before you change them, so it's best left to a shop if/when that time comes.

The rear A/C lines enter the passenger compartment just ahead of the pax side rear wheel and there is an evaporator unit and fan back there. I wouldn't suspect those just yet either.

While you wait for warmer temps, check the coolant level in the recovery tank in the engine compartment. If it's low, it will cause the heat to be sporadic.

Thank you. I can't help but wonder if the coolant temp was just too low for heat / defrost

Interesting that the compressor won't kick on if it's too cold. How does the system accomplish blowing dry air on the windshield if it's too cold?

 

[Joseph Garcia]

Regarding one area blowing cold and other areas blowing warm, that sounds like perhaps an actuator issue in your heat/cooling ducts. @swathdiver

 

[MarshMarlowe]

Regarding one area blowing cold and other areas blowing warm, that sounds like perhaps an actuator issue in your heat/cooling ducts. @swathdiver

I thought maybe a blend door was the culprit, but I couldn't duplicate the issue later

Wife tells me the blinking snowflake has stopped now. I'm thinking she started the truck, turned the heat all the way up, selected defrost, and set the fan to max. The truck struggles to warm up like that, especially when it's cold. Hoping that's all it was.

I try to tell her to give the truck a chance to make its own heat before you steal all of it for yourself, but what can you do

 

[Charlie207]

If it's below 40*F, or so, the AC & recirc system won't turn on. It's stupid; this is the 1st car I've owned that operates like that.

 

[Geotrash]

If it's below 40*F, or so, the AC & recirc system won't turn on. It's stupid; this is the 1st car I've owned that operates like that.

I suspect that the reason for this is that the compressor sits at the bottom of the A/C system, which makes it prone to "slugging" with oil after sitting for a while. At low temperatures, it's harder to clear the oil from the compressor, making damage when it's first turned on more likely. By preventing it from engaging until a warmer temp, I suspect it reduces the chances of it causing a problem.

 

[Geotrash]

Thank you. I can't help but wonder if the coolant temp was just too low for heat / defrost

Interesting that the compressor won't kick on if it's too cold. How does the system accomplish blowing dry air on the windshield if it's too cold?

It relies on heat when it's cold. Below 45ºF or so the A/C evaporator won't contribute much to drying the air anyway.

 

[Foggy]

Also, with maybe a heating issue.. Always check your coolant level..
If it's even a little low, the heat won't perform normally