07 Tahoe does A/C compressor cycle on and off?

[Brandon2489]

What pressure switch did you replace. Low or high? There may be 2. When was the last time the cabin air filter was replaced? I have seen one so dirty it's caused HVAC issues. If it's super dirty/blocked it will stop flow to evaporator and freeze it up. How long does it take for the ac to go back to normal after you shut down? In my experience the evaporator freezes up due to low airflow or an undercharged system. Have you put a set of gauges on it and just let it idle with ac on and see what the pressures do when the ac freezes up? Do you see any condensation dripping on the ground form ac system? If not the drain tube could be clogged and you could have condensation freezing up on the evaporator.

 

[Brandon2489]

If all pressures are good and system is holding pressure and you are sure there is no moisture in the system along with condensation dripping from truck and cabin filter clean then I would check the EVAP temp sensor.

 

[Brandon2489]

Also I looked at some wiring diagrams and I think there is only a low side switch and not a high side. Also looking at other diagrams the EVAP temp sensor or in some vehicles they call it a refrigerant temp sensor talks to the compressor. If the temp switch fails as in reads a super high temp then it will not allow the compressor to turn off.

 

[Brandon2489]

Also these people seem to be pretty knowledgeable on ac systems judging by the 8nfo they post. They may chime in. @Doubeleive @91RS @gpracer1 @PlunkZ71 @Rward @Matthew Jeschke

 

[avalonandl]

Yes

 

[Doubeleive]

recirculation has nothing to do with the hvac pump per sey, that's just a flap that closes and prevents outside warm air from entering the vehicle, if you have the fan turned all the way up and then press the button to activate recirculation you should hear and feel a small boost in the airflow coming out of the vents and it is noticeable provided you are parked, quiet and just sitting there monitoring the air flow. what effect it may have on the hvac pump I do not know. If it does not work then it's likely the actuator is bad and I believe that one is a bit of a pita to get too and replace. you need a tech2 to verify or some other high end 2-way scanner like a snap-on, etc. but if the pump or lines are freezing up that is probably some other issue, it is normal for the lines to get very slightly frosty under the hood or even sweaty depends on the humidity.

on a side note I have been getting a musty smell out of mine at first start up and at wot that it has never done before I might need to get in there and change my retrofit cabin filter, could have something to do with the way BB did the tune also i know there is a option to turn on the fan with the tech2 and dry it out but that would drive my viper alarm system crazy.

 

[Brandon2489]

recirculation has nothing to do with the hvac pump per sey, that's just a flap that closes and prevents outside warm air from entering the vehicle, if you have the fan turned all the way up and then press the button to activate recirculation you should hear and feel a small boost in the airflow coming out of the vents and it is noticeable provided you are parked, quiet and just sitting there monitoring the air flow. what effect it may have on the hvac pump I do not know. If it does not work then it's likely the actuator is bad and I believe that one is a bit of a pita to get too and replace. you need a tech2 to verify or some other high end 2-way scanner like a snap-on, etc. but if the pump or lines are freezing up that is probably some other issue, it is normal for the lines to get very slightly frosty under the hood or even sweaty depends on the humidity.

on a side note I have been getting a musty smell out of mine at first start up and at wot that it has never done before I might need to get in there and change my retrofit cabin filter, could have something to do with the way BB did the tune also i know there is a option to turn on the fan with the tech2 and dry it out but that would drive my viper alarm system crazy.

I have noticed if I go wot with the ac on I get a musty smell also. It's done that as long as I have had it. I believe the compressor shuts off at wot or near it. I believe that's in the owners manual. I will have to double check. I also get it at first start up too. It has been that way before cabin air filter retro and after. As long as it doesn't hang around forever then I'm ok with it.

 

[Doubeleive]

I have noticed if I go wot with the ac on I get a musty smell also. It's done that as long as I have had it. I believe the compressor shuts off at wot or near it. I believe that's in the owners manual. I will have to double check. I also get it at first start up too. It has been that way before cabin air filter retro and after. As long as it doesn't hang around forever then I'm ok with it.

ya mine has never done it until this year, kind of weird, it could be related to my tune from blackbear because i know they play with the hvac to squeeze more power out

 

[Acobrajet321]

I have an 07 Tahoe LTZ with the automatic air conditioning and rear air. I had a problem with the A/C freezing up inside the cabin causing the roaring sound and no air or a bit of warm air coming out. If I would turn off the A/C control for a few minutes and let it thaw out, It would work fine for a little while again. I also knew I had a slight leak at the rear expansion valve. Recharging didnt help the problem.
I was told different things so I replaced the rear expansion valve, the orifice tube in front (none in rear), the accumulator, the low pressure switch on the accumulator, evacuated the system. Checked to make sure I held vacuum, recharged the system and it seems to be working well. Low side pressure is around 45psi and high side is around 160psi. 40degs coming out of vents. fan slows down as cabin cools to set temp and it does not seem to be freezing up anymore.

My question is: on the 07 Tahoe, does the A/C compressor cycle on and off as needed to keep from freezing up? I am trying to get a definitive correct expert answer on this, because I get conflicting information. Some say yes it cycles, some say no it doesnt or only when the inside or outside air button is pressed.
If it is supposed to cycle on and off, what else can prevent that from happening? Is there another pressure switch? I have also changed out the Cabin Climate control module.

Thanks in advance.

Kevin

I had a similar situation in my ‘11. The AC wouldn’t cycle off, evaps would freeze over. Nothing would blow through vents even though fan motor was blasting full strength. I tried resetting vent flaps/recalibrated actuators/etc. Turning off the compressor briefly would solve the problem for a few minutes, then I’d have to do it again once it froze over again. Shop checked pressures/drew down/recharged. Everything ‘worked fine’. What I was doing was essentially ‘cycling’ the compressor myself. Found out eventually it was a bad evaporator temperature sensor. The sensor was ‘telling’ the HVAC computer the evap temp was 189 degrees. So it was always running. Never cycling off because it ‘thought’ it wasn’t getting cold enough
. Sensor is like 12 bucks....but it is mounted inside the air box completely in-accessible without removing the entire airbox...16 hour shop time per manual. Major $$$. I did Replace mine by doing a little cutting/drilling and placing it where the air filter is supposed to go on the accessible side of the evap. Took about 1.5hr total in my garage. You Need to remove airbag and need a dremel, but it’s doable without a major job. Completely fixed my cycling issue. Now it cycles on and off as I would expect it. Hasnt frozen up since. Can send a write up of what I did if you think it might help.

 

[Brandon2489]

ya mine has never done it until this year, kind of weird, it could be related to my tune from blackbear because i know they play with the hvac to squeeze more power oNow that you say that I got a tune about 3 weeks after I got mine so it's very possible the tune has some to do with it.

I had a similar situation in my ‘11. The AC wouldn’t cycle off, evaps would freeze over. Nothing would blow through vents even though fan motor was blasting full strength. I tried resetting vent flaps/recalibrated actuators/etc. Turning off the compressor briefly would solve the problem for a few minutes, then I’d have to do it again once it froze over again. Shop checked pressures/drew down/recharged. Everything ‘worked fine’. What I was doing was essentially ‘cycling’ the compressor myself. Found out eventually it was a bad evaporator temperature sensor. The sensor was ‘telling’ the HVAC computer the evap temp was 189 degrees. So it was always running. Never cycling off because it ‘thought’ it wasn’t getting cold enough
. Sensor is like 12 bucks....but it is mounted inside the air box completely in-accessible without removing the entire airbox...16 hour shop time per manual. Major $$$. I did Replace mine by doing a little cutting/drilling and placing it where the air filter is supposed to go on the accessible side of the evap. Took about 1.5hr total in my garage. You Need to remove airbag and need a dremel, but it’s doable without a major job. Completely fixed my cycling issue. Now it cycles on and off as I would expect it. Hasnt frozen up since. Can send a write up of what I did if you think it might help.

This is right on track with my last post. I suspect this may be the culprit in this case.