A/C snowflake flashing after powering down due to blown coolant line and over - heating

[intothewoodsigo]

I blew a heater core line and my 07 Denali went into safe mode and powered down the AC because of overheating. Now when I try to use my a/c the snowflake just flashes 3x and is non functioning. I read somewhere while I was waiting for a tow that it has to be reset somehow but can't find the post now that I need it working lol. El

 

[swathdiver]

I blew a heater core line and my 07 Denali went into safe mode and powered down the AC because of overheating. Now when I try to use my a/c the snowflake just flashes 3x and is non functioning. I read somewhere while I was waiting for a tow that it has to be reset somehow but can't find the post now that I need it working lol. El

Was the truck repaired when you tried to use the AC again? Not aware of a reset for something like that.

 

[intothewoodsigo]

Was the truck repaired when you tried to use the AC again? Not aware of a reset for something like that.

Yes, I had the line and coolant replaced and dash reset so there's no A/C type warnings. Everything works as it should except the A/C button (and recirc button) they both flash 3x when pressed and shut off

 

[Geotrash]

Yes, I had the line and coolant replaced and dash reset so there's no A/C type warnings. Everything works as it should except the A/C button (and recirc button) they both flash 3x when pressed and shut off

The only documented calibration (relearn) procedures are for when either the HVAC control module itself is replaced or one of the actuators are replaced. But since neither of those apply to you, I suspect something else is going on. If it helps, the following conditions must be met in order for the A/C compressor clutch to turn ON if they are not all met and an A/C request is made the LED on the A/C switch will flash:

Ambient air temperature above 7°C (45°F)
A/C low pressure switch signal circuit is grounded
A/C refrigerant pressure sensor parameter is less than 2957 kPa (429 psi)
PCM receives an A/C request from the HVAC control module
Engine coolant temperature (ECT) is less than 121°C (250°F)
The engine rpm is more than 550 RPM
The throttle position is less than 100 percent

It's possible (likely?) that's you're working with 2 unrelated problems and that the A/C quit working purely by coincidence. But I would first check to make sure they didn't knock any of the connectors loose near the accumulator on the firewall (that big aluminum can near the heater hoses) or the sensors in the lines coming from it. If all connections are good, then it's time to break out a set of A/C system gauges to read the actual pressures in the system. If you don't feel comfortable doing that, then I would take it to a local indy shop that gets good reviews.

 

[Geotrash]

All the same, here are the documented relearn procedures from the service manual:

Actuator Recalibration

When replacing the HVAC control module it will be necessary to allow the HVAC control module to perform a calibration process. When installing the HVAC control module be sure to perform the following:

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

1. Place the ignition switch to the OFF position.
2. Disconnect the scan tool.
3. Install the HVAC control module.
4. Connect all previously disconnected components.
5. Start the vehicle.
6. Wait 40 seconds for the HVAC control module to self-calibrate.
7. Verify that no DTCs have set as current DTCs.

When replacing the HVAC actuator it will be necessary to allow the HVAC control module to perform a calibration process. When installing the HVAC actuator be sure to perform one of the following:

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

Preferred Method (w/Scan Tool)

1. Clear all DTCs.
2. Place the ignition switch in the OFF position.
3. Install the HVAC actuator.
4. Connect all previously disconnected components.
5. Start the vehicle.
6. With the scan tool, initiate the Motor Re-calibration feature of the Heating and Air Conditioning Special Functions menu.
7. Verify that no DTCs have set as current DTCs.

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

Alternate Method (w/o Scan Tool)

1. Clear all DTCs.
2. Place the ignition switch to the OFF position.
3. Install the HVAC actuator.
4. Connect all previously disconnected components.
5. Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
6. Install the HVAC/ECAS fuse.
7. Start the vehicle.
8. Wait 40 seconds for the HVAC control module to self-calibrate.
9. Verify that no DTCs have set as current DTCs.

 

[swathdiver]

Yes, I had the line and coolant replaced and dash reset so there's no A/C type warnings. Everything works as it should except the A/C button (and recirc button) they both flash 3x when pressed and shut off

I suspect that either something was left disconnected (like a pressure switch) or the system was not charged properly with refrigerant and or oil. A bi-directional scan tool can see the internal codes for why the light flashes and perform diagnostics. Take it back to the people who did the repair.

 

[intothewoodsigo]

Thank you !

 

[intothewoodsigo]

The only documented calibration (relearn) procedures are for when either the HVAC control module itself is replaced or one of the actuators are replaced. But since neither of those apply to you, I suspect something else is going on. If it helps, the following conditions must be met in order for the A/C compressor clutch to turn ON if they are not all met and an A/C request is made the LED on the A/C switch will flash:

Ambient air temperature above 7°C (45°F)
A/C low pressure switch signal circuit is grounded
A/C refrigerant pressure sensor parameter is less than 2957 kPa (429 psi)
PCM receives an A/C request from the HVAC control module
Engine coolant temperature (ECT) is less than 121°C (250°F)
The engine rpm is more than 550 RPM
The throttle position is less than 100 percent

It's possible (likely?) that's you're working with 2 unrelated problems and that the A/C quit working purely by coincidence. But I would first check to make sure they didn't knock any of the connectors loose near the accumulator on the firewall (that big aluminum can near the heater hoses) or the sensors in the lines coming from it. If all connections are good, then it's time to break out a set of A/C system gauges to read the actual pressures in the system. If you don't feel comfortable doing that, then I would take it to a local indy shop that gets good reviews.

 

[intothewoodsigo]

I posted what the dash said when truck overheated which is why I thought it was related to the overheat. I'll have mu mechanic check out what you mentioned as I've already checked the easy stuff with no luck . Thanks !

 

[intothewoodsigo]

I posted what the dash said when truck overheated which is why I thought it was related to the overheat. I'll have mu mechanic check out what you mentioned as I've already checked the easy stuff with no luck . Thanks !

It was winter so I didn't have the AC on when it did this **

 

[swathdiver]

I missed the overheat part somehow! If this happened after the heater core replacement, definitely take it back and have them check their work.

 

[intothewoodsigo]

I missed the overheat part somehow! If this happened after the heater core replacement, definitely take it back and have them check their work.

It was the line that was replaced...I have an appt so hopefully an easy fix.

 

[j91z28d1]

have all the dtc cleared just incase. I thru a belt on my c6 at the track and didn't notice till the car freaked out, said stuff on the dash like that. after putting the belt on and refilling. I borrowed a scanner and there was a few codes dealing with over heating. reduce power., ac stuff like that. I cleared them all and everything worked.


the reset ac post you probably saw was one I found searching once. my wife was driving and said she couldn't use the ac cause it just flashed at her 3 times everytime she tried to turn it on. lucky for me it worked after cycling the key off and back on. but I did search here.
the fix for most people seemed to be take the battery cables off, wait about 5 mins. and then touch the two cables to each other for a bit, that will fully drain any remaining power stored in any caps in the system. then hook them back up. I think you wait a certain amount of time, or click the key forward but don't start it for a bit? something like that. if you Google tahoe flashing ac button it comes up and directs you to posts on this site if I'm remembering correctly.

 

[j91z28d1]

A/C light blinks 3 times and won't engage or turn on

Need some help. My battery died two days ago, and I replaced the battery, ever since my A/C won't engage or turn on. A/C was working before dead battery I have a 00 GMC Yukon XL SLT with automatic climate control with rear climate control. I have removed all the HVAC &AC fuses and relay's...

www.tahoeyukonforum.com

 

[intothewoodsigo]

have all the dtc cleared just incase. I thru a belt on my c6 at the track and didn't notice till the car freaked out, said stuff on the dash like that. after putting the belt on and refilling. I borrowed a scanner and there was a few codes dealing with over heating. reduce power., ac stuff like that. I cleared them all and everything worked.


the reset ac post you probably saw was one I found searching once. my wife was driving and said she couldn't use the ac cause it just flashed at her 3 times everytime she tried to turn it on. lucky for me it worked after cycling the key off and back on. but I did search here.
the fix for most people seemed to be take the battery cables off, wait about 5 mins. and then touch the two cables to each other for a bit, that will fully drain any remaining power stored in any caps in the system. then hook them back up. I think you wait a certain amount of time, or click the key forward but don't start it for a bit? something like that. if you Google tahoe flashing ac button it comes up and directs you to posts on this site if I'm remembering correctly.

Went through the computer systems with my mechanic today and it's showing very low pressure for the ac system so likely a fluke it has issues after the overheat lol.. thanks for the advice, he's going to try and track down what is likely a leak and get it fixed up for me next week.

 

[Geotrash]

Thanks for following up!

 

[intothewoodsigo]

I'm a but worried about how pricey of a fix it may be but with three rotties and 2 kids going on adventures in the summer I really appreciated my Cold AC.. has anyone had any luck with with the sealant and top up kits??

 

[Geotrash]

I'm a but worried about how pricey of a fix it may be but with three rotties and 2 kids going on adventures in the summer I really appreciated my Cold AC.. has anyone had any luck with with the sealant and top up kits??

The most likely source of a leak on these is in the Schrader valves in the high and low pressure service ports. Super simple to check for a leak (just remove the black plastic caps and spray with soapy water, as long as there is still pressure in the system). If a leak is found, the shop will properly evacuate the system, replace the valves, draw down a vacuum, and recharge it with the right amount of r134a, by weight. Shouldn't be more than $200 total.

In fact, if you have the system serviced at all, ask them to replace those Schrader valves before they do it.