Need Air Conditioning Help

I have a factory A/C system that I'm trying to get working. I pulled a vacuum on the system and it tested good with no leaks. I left it overnight and it the vacuum gauge didn't move at all so I decided to charge it up. I put in an oil charge first, and then added a can of refrigerant. The compressor started to make noise, felt really hot, and seemed to bog down the idle so I cut the A/C off and am now looking here for ideas about what might be going on with the system and what I should do to get it fixed and working right without noises or problems?

 

They make a solvent for flushing A/C systems. I make an adapter out of a spark plug boot and put a funnel on one end and stretch the other end over the tubes to pour a few ounces onto the condenser, evaporator and the lines. Hold a rag over the outlet end and blow air into the other end and make sure everything is open. It sounds like something is blocked, maybe the expansion valve. Is your dryer/filter new? Something's blocked.

 

Was it a new compressor? Did you put any oil in the compressor directly prior to attaching the hoses?

You'll want more than one can of freon in the system before test running the system. Hardly anything will be pushing the oil around with less than a pound of freon in the system.

 

Everything in the system is new or rebuilt and oil was added to the compressor before it was buttoned up. I've managed to get about 2 & 1/2 cans of freon in the system altogether. Is there a way for me to pinpoint what the problem might be? The compressor squeaking and bogging the engine down is bothersome.

 

You need to put a set of gauges on it to see what your pressures are. Possibly restricted, incorrect charge, incorrect clutch air gap, too much oil, overcharge, etc etc

 

I got the A/C system working on my Buick just last month (A4 unit though), and it did squeak scarily for about 30 seconds before quieting up. However mine compressor was junkyard sourced (blew oil/freon when I removed the lines so assumed it was good) so I wasn't overly surprised and glad when it quieted down.

Definitely get a set of gauges on it, high and low preferrably. R134a requires a bit more pressure than R12 for similar results. I added freon to mine until the high reading was right at the upper specification that the manual called for with R12. It does bog the engine down pretty good at idle if you don't have the solenoid that bumps the idle while the compressor is on.

 

What refrigerant did you use? Gauges are a must. Did you change the txv (refrigerant metering device)? If you put oil in the compressor you shouldn't need more

 

I had a chance today to mess with it a little more. All the gauges I come across are for 134a and I'm using R12 I need to find a set that will do both. I did have a gauge that came with an old recharge kit that is for R12 and reads both low side and high side and ranges from 0 to 400 PSI. Only thing is you can only read one at a time unlike with the manifold gauge sets. I checked the pressure before starting the car and both the low and the high side read 81 PSI. I cranked it up and set it on MAX A/C. At crank up it runs about 2000 RPMs and as it warms up it will settle down to 1000 to 1500 RPMs. The POA valve and the inner line on the compressor both got really cold and had frost forming on them. I reached inside the car and it also was cold. The compressor also didn't seem to bog the engine down or make noise like it did before, but I didn't run it as long today as I did a couple of days ago. Maybe 10 minutes max just to get the pressure readings. Running on MAX A/C the low side read 25 to 35 PSI and the high side read around 200 to 205 PSI. When I shut the A/C off with it running the high side dropped to about 150 PSI and the low side to about 20 to 25 PSI. The only oil I added to the system was a 4 oz oil charge which adds about 2 oz to the system. I did this because it has been a long time since the system has been opened up or charged just as a safeguard.

 

Did you change the txv?

 

I haven't changed the txv, but all components in the system are new or rebuilt. I'm not sure why I would need to change it since I am using chemicals that the system was originally designed to use? Do the pressures give an indication that the expansion valve is the problem?

 

Well it is a metering device...For that high of a head pressure and low on the low side show issues.. Air in the system (did you purge the hose of air after connecting it to the refrigerant container every time a new one was used?) Is air flow across the condensing coil best it can be? That high on the high side is why it made the sounds it did.

 

I didn't purge the hose of air after connecting to the refrigerant every time. Could it be undercharged? Not sure about air flow across the condensing coil or how to test that.

 

I've got an old chart for a four-season air conditioning system and I'm not sure if it is the same but for a temperature of air entering the condenser at 90 degrees the compressor head pressure should be 200-210 at 2000 rpms which is where it is and the evaporator pressure at the POA at sea level is 29.5 psig, 30.0 psig at 1000 feet and increases by 0.5 psig for each 1000 feet in elevation. I look to be right at these numbers. What is indicating that there is an issue? Should I be getting different readings and if so what should they be?

 

Those pressure numbers seem high to me, but its been a long time since I looked at POA and continuous duty A/C system specifications. If the book says that is what they are supposed to be, and you have cold air at the vents, I'd say you are good there. The cooling efficiency will increase going down the road with more air passing through the condensor.

If it's still screeching then you probably have something failing in the compressor, and may want to swap it out before it starts throwing too much trash into the system and require you to replace other parts of the system from contamination. If it didn't make anymore scary noises, I'd say you are done and go enjoy the car.

 

Did that once while charging my Silverado, Sounded like stones in the compressor within a few seconds of opening the valve. Got distracted when a buddy asked me a question. Ruined the comp almost immediately.

 

Yikes, I hope I haven't torn anything up.

 

Had nothing to do with not purging it. There was a bulletin on the Silverados about liquid slugging the compressors, especially after/during a recharge, (idealy, the system should be charged and allowed to equalize before running it). GM made a new re-routed suction line to fix it...

 

When you dint purge the lines of the air it raises the head pressure... Air also mixes in and turns to acid. Temp and pressure charts are useful. I like my head pressure to be in the 100s. The txv. Has a cap tube with a bulb filled with the same freon the AC system was designed to be used with. Hints the reason singe guys have problems using 134a. It doesn't meter correctly. Good luck I hope all continues to be well. An old txv that doest meter right will cause high head pressure.

 

You guys talk about pressures but you don't say what the load is on the system. To fully load the system put all the windows down, open the outside air vent and run the fan on high. That will put a full load on the system. With the windows up and the fan on low, in re-circulate mode the pressures will be at least 50 PSI lower on the high side. Worst case is when you have a car at operating temp, shut it off and let it sit in the sun for 20 minutes and let the interior get to 140 degrees at that point the heat soak under the hood is at max. Put gauges on it, start the car and watch the high side go to 325 psi. The temperature conditions (interior, under hood and outside) will greatly effect the pressures.

 

With the pressures I had of ~ 35 and 205, the windows were down, A/C on, fan on high (not recirc), car idling at 1500-2000 rpms, ambient temp between 80 and 90.