A/C not working blows hot air

Good afternoon,

I do not understand your numbers.

First static pressures should be equal with the engine off and almost the same pressure as the outside temperature.

Running, the high side should be 2 times ambient air plus 15%.

The low side should be 25-30 solid no matter the temperature.

Can you recheck those values?

Roy

Okay.

As I stated, yes, the expansion valve and the dryer need to be changed.

There is no compressor control valve.

Roy

No, it would not.

Besides, the expansion valve is not controlled by the compressor.

Roy

Yes, the expansion valve is causing both issues. If the pressures do not equalize, the valve is closed.

Roy

You are welcome.

Always glad to help.

Roy

Hello,

It sounds like the system is over full the high side reading should not be over 325 PSI but to be sure here are two guides to help us find out whats going on.

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

and

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Please run down these guides and report back.

If you saw a/c dye in vents then it is a pretty good thing that your evaporator is shot which will require HVAC unit to come out and probably dash. Have a mechanic check for evaporator leak to verify before doing this as it is a big expense.

Hi fleetwin. Welcome to the forum. The easiest thing to do is find another similar car and see how it compares. According to two Chrysler trainers from many years ago, AC systems are only intended to lower air temperature 20 degrees. The real comfort comes from the removal of the humidity.

Some systems will have a duct temperature of as low as 40 degres which is actually a bad thing. The humidity condenses and collects on the cold evaporator in the heater box. That moisture runs into a drain pan and drips onto the ground. There are mechanical or electronic controls to slow the flow of refrigerant to prevent the evaporator from getting colder than around 40 degrees because that moisture would freeze into a block of ice and block air flow. The symptom would be real good cooling for a few minutes, then no more cold air from the ducts.

One thing you can check for is excessive frost on one of the hoses under the hood near the firewall. A liquid must absorb a lot of heat to turn into a vapor. It is supposed to evaporate in the, ... Uhm, ... Well, ... Evaporator, hence the name of the part. The point of evaporating is where it gets real cold, and you want that to be inside the car. Two things can cause that to occur in the wrong place. First, if there is not enough charge in the system, the liquid will vaporize in the hose leading to the firewall. Where that occurs you will see water condensation on the hose, or more likely, frost. Some water on the hose is normal because the refrigerant will be much colder that outside air, but a lot of frost is not normal.

You were correct in your first post. "Recirculate" is meant to quickly cool the interior by blowing previously-cooled air over the evaporator. This will remove humidity rapidly and is the most effective setting when using higher fan speeds. Once the car is cool, the other settings introduce fresh outside air and expel stale air. There is more work to do so slower fan speeds will allow the system to be more effective. You want the air to move slowly so it will stay in contact with the cold evaporator as long as possible. Also, there is a limit to how much heat can be removed in a given amount of time. At higher fan speeds, more air with more BTUs crosses the fins of the evaporator. When the number of BTUs exceeds the capacity, more are not removed so the air temperature remains higher.

Caradiodoc