Decided to mess around with the AC on my car today. It's to hot to drive above 80 or so currently.
I had a recharge kit with the Guage laying around so I put it on, was low. Won't take anything more than about 32 or so psi. Compressor definitely kicks on. But the air isnt cold cold. Ill check the actual temp another time.
First question. Since it maxed at 32, and i didn't evacuate the system. Could I need to have it all pulled out before refilling?
Second- since I don't have any plans of chasing down actuators. I dont care where the cold air comes from. Should I have it recharged by a pro before bothering with the blend door?

 

Not a lot to go on from your description. It sounds like your system had not lost its entire charge because your compressor was running and pulled in R134a from a can. How many ounces were in your recharge kit? It is tough to do diagnostics if you dont start with a correctly charged system. An undercharged system will have poor air outlet temperature but an overcharged system will too.

 

Without a real set of manifold gauges it's really hard to guess at what is happening inside the system. Best advice is to either buy a set of gauges and report back, or bring it to a shop to have the system properly evacuated, leak tested, repaired, and charged.

 

Kind of what I was figuring. Naturally I would have loved a viola moment. But at least this way I know the compressor will kick on.
thanks

 

You can always rent a set of gauges at most auto parts stores.

 

I wouldn't know what to do with them. I think this is a job for someone else.

 

OK - So first off - I'll agree with everyone else that the proper way to charge the system is by refrigerant weight, and having a set of manifold gauges so you can see both high side and low side pressures is important to know what's going on....

BUT - with a R134a system - a lot can be deduced by knowing the low side pressure.

So - CMC76 - what was the ambient temp, and what was the low side pressure that you were reading ???

 

It was about 89 degrees, very high humidity. Low side pressure was about 32 -34 psi

 

So - assuming that the pressure gauge reading is accurate - it looks like the low side pressure is low (see below). There are multiple possible causes - and this is where knowing high side pressure would be helpful - but if it were me - I'd try adding some more R134a to try to get the low side pressure up to about 50 psi (@ ~90 degrees), and see if that helps. If it does help - you almost certainly have a leak in the system - and you will need to figure out where it's leaking. The way a pro does that is they inject a bit of UV dye into the system, then run the car with A/C on for a while, and then look at the engine compartment with a black light - the leak is normally pretty obvious. You may get lucky and the leak is just a bad "O"-Ring - but to repair that you have to change the "O"-Ring - evacuate the system, and recharge.... .



Temperature Low Side Pressure High Side Pressure

in oF in oC in psi in kPa in psi in kPa
65 18 25 – 35 172 – 241 135 – 155 931 – 1069
70 21 35 – 40 241 – 276 145 – 160 1000 – 1103
75 24 35 – 40 241 – 310 150 – 170 1034 – 1172
80 27 40 – 50 276 – 345 175 – 210 1207 – 1448
85 29 45 – 55 310 – 379 225 – 250 1551 – 1724
90 32 45 – 55 310 – 379 250 – 270 1724 – 1862
95 35 50 – 55 345 – 379 275 – 300 1896 – 2068
100 38 50 – 55 345 – 379 315 – 325 2172 – 2241
105 41 50 – 55 345 – 379 330 – 335 2275 – 2310
110 43 50 – 55 345 – 379 340 – 345 2344 – 2379


Based on the readings from the pressure gauges, you can further diagnose the problem with the help of the following table.

Low Side Pres High Side Pres Diagnosis

Within range Within range No problem. AC is working fine.
Low Low Refrigerant is Low. Add some refrigerant.
Low High Possible Blockage in Expansion Valve or Orifice Tube.
High Low Problem with Compressor. Service or Replacement.
High High Refrigerant Overload. Vent extra R134a.

 

Appreciate the information. I'll see what I can find out

 

You have said this is something you are not comfortable working on yourself and that is very understandable. You have a system that runs and is able to freeze up your evaporator on a summer day. That can be a good thing because it suggests your compressor is working. I do want to caution you about just adding charge if you do not know what to look for. In your first post you explained that you used a recharge kit. I have seen various weights of R134a so you may or may not have already overcharged your system. Since your system pulled in charge we know it was not empty. Continuing to add and add charge beyond the 26 or 28 ounce charge can lead to compressor and performance problems.

Too much charge will increase the high side pressure. This makes the compressor work harder. It can also lead to cycling the compressor on and off with the high side pressure setting (about 400psi) which is not the type of duty this variable displacement compressor is designed to do.

Too much charge will increase the amount of liquid refrigerant that exits the evaporator and enters the accumulator dehydrator. It is normal for the accumulator to be partially filled with liquid and the rest is gas. Its job is to separate out the gas, store the liquid, return oil to the compressor, and not allow liquid refrigerant to flow to the compressor. Too much charge will fill the accumulator to the point where it allows liquid to flow to the compressor. Pumping liquid refrigerant is bad for compressor life.

 

The best way is to recover and evacuate the the system, then weigh in fresh refrigerant, with the drum already on scale and zeroed or called tare, in garage so wind doesn’t blow jug around and get you weight that keeps jumping around.

Used to be HVAC/Refrigeration service tech, not anymore professionally, but have all the tools needed, scales proper R134a refrigerant gauges just for my/friends family cars.

The fact you know exact capacity makes it easy to just weigh it in, and know it’s right.

It’s going to be cheaper to take it to ac shop and have them evacuate and weigh in fresh refrigerant, they can even add dye.

Cheaper than buying scale, gauges, vacuum pump etc.

However if you are playing around with several cars it might be worth it to buy the tools.

For me it got to be a pain, everyone wants their A/C fixed free, and people come out of the woodwork wanting free labor and free refrigerant, so maybe keep it a secret.