A/C question for all those HVAC gurus

[Cadi Cat]

All A/C systems are equipped with what is most knowingly called a 'Thermal Expansion Valve', correct? What ever it's called in a typical passenger car, would a new valve, or if applicable a simple adjustment to it allow for colder air since it controls the refridgerant flow to the evaporator? My A/C system is fully charged working properly and comfortably cold but would like to get a little bit more cold air flowing into the car. Would doing something like this (if possible) provide positive results without destroying my system with a small simple tweak?

[ewill3rd]

No and No.

Not all cars use TXV's to control cooling, some use orifice tubes.

TXVs are not adjustable, they are set to as close to freezing as possible and sealed. If you put it below the freezing point then the evaporator begins to ice up and the system stops working.
You can only cool air so much, using recirculation mode can greatly increase cooling capabilies but the systems are limited to the laws of physics.
This stuff was figured out like 30 years ago pretty much, believe me if they could do it, they would.

[R-Caddy]

If you find other glitches in you HVAC system operation, check out the control panel itself.

[TitanCTS]

Be sure there is no leaks in the system and the proper amount of refrigerant and oil is injected into the car. Our cars take alot of refrigerant for the size of the system it has. I had to replace the high side service port on my car because it slowly leaked out refrigerant over a long period of time until the system stopped working. You might want to consider another recharge but this time have the tech working on the car pull vacuum for at least 45 minutes. That should sufficiently boil off any remaining moisture in the system. If that does not work then you always try a new accumulator also known as receiver/dryer. The coldest the temps will ever reach on any A/C equipped car is 35 degrees. Any colder and things would freeze up. The HVAC system automatically recirculates when the A/C is switched on.

[Cadi Cat]

Originally Posted by R-Caddy

If you find other glitches in you HVAC system operation, check out the control panel itself.

yeah... I considered that. The panel seems to be working fine... to me anyways. But also thought that maybe the inside temp sensor may not be functioning properly? It's not that big of a deal. I'm just trying to find ways to make it a little colder. I'm gonna try blowing compressed air through the coils and see what that does.

[Cadi Cat]

Originally Posted by TitanCTS

Be sure there is no leaks in the system and the proper amount of refrigerant and oil is injected into the car. Our cars take alot of refrigerant for the size of the system it has. I had to replace the high side service port on my car because it slowly leaked out refrigerant over a long period of time until the system stopped working. You might want to consider another recharge but this time have the tech working on the car pull vacuum for at least 45 minutes. That should sufficiently boil off any remaining moisture in the system. If that does not work then you always try a new accumulator also known as receiver/dryer. The coldest the temps will ever reach on any A/C equipped car is 35 degrees. Any colder and things would freeze up. The HVAC system automatically recirculates when the A/C is switched on.

well it's still held its charge from the factory. All i did about 2 weeks ago was add some pag oil and checked how well it was charged and all is good. Does the refridgerant get 'old' and starts to loose its cooling ability? Because i know for darn sure that my a/c does not run at 35 degrees. Maybe 45-50. Does anyone know how cold this system should run?

[ewill3rd]

Getting temps in the 30's would depend on a lot of stuff, not the least of which would be the ambient weather.
Air conditioning can only cool the air a certain amount at a time. I think it is like 6-10 degrees. The recirculation mode lets you keep cooling the air more and more to get it down where it is nice and cool in your car on a hot day.
Ambient temp, humidity, the efficiency of the condensor and fans, and the settings you have the system on can all affect how the system operates.
Ideal conditions are going down the highway in recirc at a nice cruise, you could set the a/c system on max cold recirc and it should get uncomfortably cold after a while.
Driving in traffic on a hot sunny humid day you may never even get the inside air temp down to 60. You aren't driving around in an energy efficient home.
You are letting direct sunlight in, you have vents in the body that allow a lot of heat back into the car, you have lots of accessories like the radio generating heat.... etc.

Don't start throwing things at your car because it doesn't work the way you think it should.
Adding too much oil can actually degrade system performance and even damage components like the compressor if you go overboard.
The only way to check the system charge is to evacuate it and weigh the refrigerant, and recharge it with the specified weight.
You can play with gage readings to get the operating pressures inside a certain window but depending on the weather it could vary.

I still haven't really seen any indication that something is really wrong with your system.
I'd hate to see you mess it up trying to get it to work better.

[Cadi Cat]

Originally Posted by ewill3rd

Getting temps in the 30's would depend on a lot of stuff, not the least of which would be the ambient weather.
Air conditioning can only cool the air a certain amount at a time. I think it is like 6-10 degrees. The recirculation mode lets you keep cooling the air more and more to get it down where it is nice and cool in your car on a hot day.
Ambient temp, humidity, the efficiency of the condensor and fans, and the settings you have the system on can all affect how the system operates.
Ideal conditions are going down the highway in recirc at a nice cruise, you could set the a/c system on max cold recirc and it should get uncomfortably cold after a while.
Driving in traffic on a hot sunny humid day you may never even get the inside air temp down to 60. You aren't driving around in an energy efficient home.
You are letting direct sunlight in, you have vents in the body that allow a lot of heat back into the car, you have lots of accessories like the radio generating heat.... etc.

Don't start throwing things at your car because it doesn't work the way you think it should.
Adding too much oil can actually degrade system performance and even damage components like the compressor if you go overboard.
The only way to check the system charge is to evacuate it and weigh the refrigerant, and recharge it with the specified weight.
You can play with gage readings to get the operating pressures inside a certain window but depending on the weather it could vary.

I still haven't really seen any indication that something is really wrong with your system.
I'd hate to see you mess it up trying to get it to work better.

Nothing really wrong with my system I was just curious and asking for suggestions. And I thank you. My recirculation mode fogs up my windshield with the a/c on. I've tried that once to see if it would help because it just makes sense. But it just fogs up.

[TitanCTS]

The refrigerant does not get old as you would think. Over time depending on how much you use it. The system will accumulate enough moisture to degrade performance. You can't jus add PAG oil when the system is fully charged. PAG oil can only be added when there is no pressure in the system and it must be vacuumed. If you want to, recover the system, Vacuum it for 45 minutes. Add 35mls of PAG oil, Fill it up with .95Kg of refrigerant and you should be able to have consistent 35-40 degrees out of the vents on the lowest temp settings. The system automatically recirculates when the A/C is switched on. Pushing the Recirc button does not do anything when the A/C is on.

If you want, buy a cheap UV flashlight from autozone and go over your a/c system to be sure that no refrigerant is leaking, be sure your drain holes in the HVAC box is clear of debris. Make sure no trash is entering the pollen filter that could eventually clog the evap drains. If your windshield is fogging up it could be a good indication of excessive moisture in the evap box not properly draining.

[ewill3rd]

There are ways to inject oil in a charged system, but as I indicated before you need to be sure you have a reason to add it. Don't just put it in unless you know some has leaked out somewhere.

The UV light is a great idea to find possible leaks but you would have an indication that it is low, and it would have to have tracer dye in it.
GM puts tracer dye in all production cars now, but didn't years ago it has to be added to a '98. Once it is in there, it is in there.

Again it doesn't really sound like anything is wrong.