Rep Power: 0

Just finished the repair and I'm very disappointed with the results... it's 96 outside and I could only get the vent temperature to 78. At 2000 RPM the high side read 350 PSI and the low side read 35 PSI. I added 23 ounces of freon...

I doubt that's how it's supposed to work...I was parked the whole time if that matters though. I know the airflow should help it.

 
Rep Power: 519

You got maybe a 20 degree drop. It's working a little, but not efficiently. Or the heat is still on.
Actually, just plugging the numbers into a calculator, it says this could be acceptable vent temperature for a random condition near this.

Off the top of my head, the high side pressure looks high. But I don't know enough about what went on to say that yet.


You say 78 vent and 96 ambient.
What is the humidity?
What is the air temp at the blower intake--inside the car, with recirculate on?

IS the condensor fan running? Is it running fast and moving a lot of air, not wimpy at all? Correct direction?

HOW did you measure the freon charge? My first thought is it is overcharged.
Other factors that I am not aware of may be in play too.


Feel the suction line coming out of the firewall. Cold? What is the temp there?
What is the temps of the condensor inlet and temp of the outlet lines? How much temp drop is the condensor giving?

Is the heater core water valve turning off completely when the temp is set at max cold?

Are you using recirculate?

Did you evacuate the system for any length of time prior to charging it? Leftover air in the system takes up valuable space.

Is the condensor aftermarket? Does it have the same volume and design as the original?

 
Rep Power: 0

Well the system suddenly stopped working tonight. I was on my way home, and I tried switching from recirculated to fresh air. It didn't cool off much, so I switched back to recirculation. It didn't cool at all then, and I started hearing the compressor belt lightly chirping.


As for the questions I'm able to answer:
This week we have a somewhat steady humidity around 54%.
I don't have the intake temp, but I had previously held the thermometer close to me and read 80 degrees inside.
The condenser fan was running. It's mounted on the engine side and was pulling air towards the engine. It was pulling a fairly large amount of air.
I charged the freon by weight. I added what weighed 23 ounces.
The condenser is aftermarket. Its design seems to be identical to the original condenser, except that the bolts weren't aligned 100% perfect.
Lastly, I evacuated the system for an hour and a half before charging. I left the vacuum alone for an hour and it stayed stable at -27 inches of mercury. The vacuum failed to reach the 75 microns it was rated at.

ADDITION: A few other noteworthy things. The 350 PSI high side and 35 PSI low side were at 2000 rpm, not 1500. At 1500 the low side read too high (I don't have the exact number). Also, my dad was inside during the charge. He said it continually got colder while I was adding the first can. During the second can it never changed though. It neither cooled any more nor warmed up any. It has the old belt on, as I didn't feel comfortable removing the engine mount for it. I changed out the old alternator belt, and it's tensioned correctly. The system was cooling 29 degrees while driving 50+ mph (recirculated). I used both a suction side and liquid line filter.

 
Rep Power: 519

Ummm. It quit? What happened, and what does it do NOW? What pressures does it give now? Did the compressor crap?

It sounded overcharged before.
A non-OEM condensor could have a smaller capacity, and that would make the total system requirement less than original if it did. It could also make efficiency suffer if the condensor holds less...

Is the expansion valve new?



I use feel a lot during AC work.
There needs to be a significant temp drop between the inlet and outlet of the condensor. An easy 40-50 degrees drop, but that depends on other conditions too.

The liquid line should be the same temp from the cond. outlet all the way to the expansion valve. If there is a big temp drop through the drier or your filter(s), then there is a restriction that shouldn't be there. Fix that.
The temp of the line OUT of the evaporator (expansion valve, suction line to the compressor) should sweat and be cold if there is enough freon going through the evaporator.



I'm really not sure what to tell you at this point.
See what you have and start there?

 
Rep Power: 0

Well it turns out all is not lost -- except a lot of freon. When I went to inspect it this morning, it began blowing out its coolish air. I gathered some more info for you (all done stationary):

I started out in 78* outside. The fan blew 60* with recirculation on.
The low pressure side had 45 PSI. The high pressure side had 125 PSI.
The low pressure hose was 60*, and the high pressure hose was 84* by the valves.
The condenser hose was about the outside temperature where it left (by feel). I couldn't get good contact to measure input/output.
The evaporator input measured 85* (bad contact) and the output measured 59* (~the same as in the car).
The temperature was 80* outside after these twenty minutes. The entire low pressure hose was covered in water (good sign).

According to our weather forecast, humidity is 52% and the dew point is 60*.


Now...for why it lost this huge amount of pressure and quit working last night. I know there's a high pressure sensor on the drier, so maybe that forced the system to shut down. Also, there's no good explanation I can think of for the insane leak. It held a vacuum for about an hour...This leads me to guess that maybe the high pressure relief on the compressor released it? I expected to hear a machine gun sound if it did...but the system has been running smooth and quiet. Is there a chance that my probably-overtightened O-rings held under vacuum then shot it out under pressure?

 
Rep Power: 519

Where did it vent (what area or component)? Are there any big oil stains around any of the fittings, seals, or the relief valve?

What were you doing when it vented?

I don't remember if that car has both a pressure cutoff switch and a pressure relief valve. A valve would vent around 450-500 psi. The cutoff switch should have shut it off a little bit lower than that.

You need to figure out WHERE it lost the freon at. It sure could have popped an O ring or something.

Is the expansion valve new?


You listed a bunch of temps now AFTER it burped some freon out.
Need pressure readings at the same time.


Found this... General principles:
FOR AUTO AIR CONDITIONING R134a SYSTEMS:
At IDLE - Condenser inlet temp 170 to 180, Condenser Outlet temp 135 to 150 (usually a 30 to 40 degree drop in temperature across the Condenser), Evaporator Outlet temp 45 to 55, Compressor Suction temp 60 to 70 (usually a 15 to 20 degree drop in temperature from the evaporator outlet to compressor suction port). With the engine IDLING, you want to adjust the charge so the line at the Compressor suction port is about 10 to 20 degrees WARMER than the Evaporator Outlet pipe, and with the engine running at 1500 to 1800 rpm, you want the line at the Compressor suction port to be about 2 to 10 degrees WARMER than the Evaporator Outlet pipe.
At 1500 RPM - Condenser inlet temp 190 to 200, Condenser Outlet temp 135 to 155 (usually a 40 to 60 degree drop in temperature across the Condenser), Evaporator Outlet temp 45 to 55, Compressor Suction temp 55 to 60 (usually a 7 to 12 degree drop in temperature from the evaporator outlet to compressor suction port).
At 90 degrees ambient, for R134a systems, look for about 200- 220 Pressures on the high side and about 25-30 Pressures on the low side at idle, and at 1,500 RPM look for about 220- 230 Pressures on the high side and about 20-27 Pressures on the low side.

The next line says to watch it cycle at a certain pressure, yours won't. Yours does not cycle on pressures. It cycles on evaporator temperature. (IIRC, didn't look)

Anyway, this is where I found that http://www.schnitzer.net/dana/ac_temp_basics.html

 
Rep Power: 0

I included pressures there. It was 45 PSI low and 125 PSI high (from 35 and 350).

The system has both -- the high pressure cutoff switch is on the drier, and the pressure relief valve is on the compressor. Thus far I haven't been able to spot any oil stains (and I was driving when it vented).

The expansion valve is new -- I wasn't 100% sure about its installation. The old one was crimped hard and forced into a clip. Crimping it seemed like a bad idea, as it would probably damage the sensor. I left it uncrimped but managed to squeeze it into the clip and taped it tight with the original tar-based tape.
It has good contact, but only as good as two cylinders would get. I would have used electrical tape -- but it seemed like too harsh of an environment inside for it (in case these details matter here).

There's also a good chance the system is high on oil -- The compressor said it came with 130 mL of oil, so I double checked it by draining extremely thoroughly. Only 115 mL came out, and there were some minor spills during installation, so I added 20 mL extra. Maybe some was trapped somewhere hidden in the compressor? I had drained the evaporator and replaced every other component during the installation. I changed all but 4 extremely clean lines. (high pressure valve line, and the low pressure lines)

Would overtightened O-rings hold a vacuum but then spill out at high pressure? I went by feel because I have the wrong-sized torque wrench and I've never seen a tool for torquing where two pipes meet.

 
Rep Power: 519

Ok, duh, pressures were there, I can't read.

TXV (Thermal Expansion Valve)...Its job is to regulate freon flow into the evaporator, based on outlet pipe temperature.
The bulb is supposed to be firmly clamped against the outlet pipe, so the bulb actually has to become the same temperature as the evaporator outlet pipe. (I know there isn't a lot of direct contact between 2 round tubes, so it needs to be clamped tight.)
The bulb-pipe connection is supposed to be wrapped in asphalt tape (or DUM-DUM?) to insulate it from any possible warm air in the evap housing. (black tape would melt off).
If it isn't all proper, that could cause false freon flow regulation into the evap core--and therefore false temperature regulation.

That capillary tube to the bulb must not be kinked or bent, that would kill operation of the TXV. Smooth bends are a must.


The AC thermostat sensor probe (thermocouple) is supposed to be in a certain place and depth in the core of the evap. Sticking it in randomly could make the system (clutch) cycle at the wrong temps.


The high pressure relief valve should probably be replaced now that it has popped open, according to my info. It could now open at too low pressure and vent when it isn't supposed to. (ASSuming that is what let the freon out!)


Yes, the amount of oil in the system is critical. C&P:
If there’s too little oil in the system, the
A/C compressor can make noise or possibly fail. If
there’s too much oil in the system, the system’s
cooling capacity is reduced.

Sounds like you now have (had?) 150mL of oil in it. (Maybe less, now that it vented some pressure off.)

O rings on these don't normally rely on torque to seal. Torque only holds the fitting together. (Maybe I am not thinking of the same fittings you are, IDK.)



CSB: I have seen strange stuff over the years, not just O ring problems. I saw a chunk of aluminum AC pipe on a 6th gen that had been rubbed through after a crash, but had a flap of metal covering the hole. It held vacuum great but leaked like hell under any pressure. The flap was acting like a check valve.






What I would probably do: Once you get this corrected and back to a place where you can charge it, start off with too little freon (like 16oz.) Run it, watch pressures and let it stabilize temps. (use a thermometer in the dash vents) Add one oz at a time, watch vent temp for several minutes after each additional ounce. Stop when it gets cold LOL.

 
Rep Power: 0

I've finished installing every part last week and took it to a shop yesterday. They vacuumed the system and added freon. A/C blows old now <3 Thanks

 
Rep Power: 519

Great.
Now go over to michael3n's house and fix his car.

Thx.






LOL