Another ac charging problem
 

Sorry for posting another AC charging problem. Yes, I have read most of the AC threads that have previously posted, but, that being said, I may have missed something. Car is an 89 3.2 Carrera. Evacuated the system for several hours, left overnight and still had same vacuum as night before. Gauges on, car started, freon attached, removed air in freon line and opened up the low pressure side. Freon seemed to get in system but could get only maybe 4-5 ounces in. The low side pressure was high, about 100 when charging. When looked at the low and high, freon closed, about 20 low and 100 high. I then went to see if I had an expansion valve and I did, except, it was for a 928. Any ideas, other than the expansion valve. The system did previously work but was leaking on the compressor seal and replaced with a user compressor from a PP person. So I guess it could be the expansion valve or the compressor. Any help will be appreciated. Steve

:confused:

High side / low side differential indicates compressor is working. If it was toast pressures would be close to each other.

Not trying to be a stinker, but are you absolutely sure you used the equipment correctly when pulling the vacuum/evacuation? Intent of the question is to make sure the path was open into the system.

When you say "Opened up the low pressure side" that means the gauge knobs, right? To allow freon to flow into the blue hose? R12 is your refrigerant? If R134, then there are also knobs at the compressor fittings. Just being cautious - not flippant.

Expansion valves are cheap and if you do that, throw on a new R/D.

You can also check the R12 sight glass. Just a few ounces in should show it pretty empty. If you are seeing bubbles, you probably have more than just a few ounces in there.

~20 low should be drawing refrigerant from the supply tank....unless its empty?

Your system is still undercharged. Make sure you warm up the fren can because when the can freezes, tha vapor will not come out of the can. I usually just get a bucket of water and immerse the freon can to warm it up.

From a fully evacuated system, with the engine off, it is faster to charge the first can in liquid on the high side with the can in inverted position, then close the high side charging valve, let the system low and high side pressures stabilize, then charge the remaining freon by vapor or gas on the low side charging valve with the can in upright position with the engine and compressor running.

CAUTION, EXTREME CAUTION.

DO NOT "WARM" A CAN/TANK OF REFRIGERANT>

WARMING the can/tank/container beyond typical sumer ambient temperature can be DANGEROUS. They are not rated to contain the level of pressure which might result with "warming" them.

Just because frost forms on the outside of the can does not mean that refrigerant is not flowing, in fact the exact opposite is the case.

If you have a propane powered grill then take note of the frost line on the tank as you use up the propane gas, same effect with those refrigernat "cans".

Just because the can freezes certainly does not mean the gas is frozen! There should not be any water to freeze in the system.

:confused:

Jusr use tap water. There is no harm in that. I have been working on commercial and residential and mobile a/c systems for a long time.

+1 Bob and wwest.

Is this R12 or 134a? Just to double check (since I didn't see it mentioned), you had engine running (ideally 1500-2000 rpm), decklid down (resting on hoses) a/c fan and a/c temp control both set to max, yes?

"CAUTION, EXTREME CAUTION.

DO NOT "WARM" A CAN/TANK OF REFRIGERANT>

WARMING the can/tank/container beyond typical summer ambient temperature can be DANGEROUS. They are not rated to contain the level of pressure which might result with "warming" them."



BS, unless your summer ambient is 125 degrees F or greater.


Amazon.com: Robinair 10994 300-Watt Heater Blanket for Refrigerant Tank: Automotive

Steve911T - Um hello - you going to respond or let us speculate??????

To all, thank you for your replies. It was 92 degrees out so I did not have to heat the freon and it is 134A. I think my main problem is that the system is unknown. System was updated some time ago and when I bought the car, the wire to the compressor was disconnected. The fan up front in the hood to blow the air over the front condensor did not work (replaced) and the original compressor was leaking freon around the main seal. As I said, compressor replaced with a used one. The Dryer was replaced with a new one. As far as evacuating the system, it was evacuated with all the correct knobs open, low side. It did hold vacuum overnight. Any way, as I said, the main problem is not knowing what is good and what is bad. The expansion valve looks to be original so that needs to be replaced, the compressor seems to be good, so I will try again in about a week with a new EV. One thing that did bother me was that there was oil in the lines that dripped out after I had removed the gauges. I did put the correct amount of ester oil in the system per the Haynes manual. Steve

Bob, sorry for the delay but the digust factor was pretty high. I also bought a brand new 6500 BTU AC (at a yard sale) for my workshop/garage area and installed it. Yes, that worked fine. I am getting sick of working in 85-95 degree temps. Steve

Evacuation should be done through both the low and high sides. Only close the high side valve on the A/C gauge manifold when you begin charging with refrigerant. Are you using a 2-stage mechanical vacuum pump? The venturi type that uses compressed air will not achieve a sufficiently low pressure vacuum. 911's should be evacuated for at least three hours with the car sitting in the sun if possible. Prior to shutting down the vacuum pump, are you closing the valve on the vacuum pump? If not, vacuum pump oil can be pulled into the A/C gauge manifold and hoses. Expansion valves (TXV) are rather dependable. Before replacing the TXV, I would make sure you truly have all the air out of the system. If you do replace the TXV be sure and put the "Prestite" (tar-like insulating compound) back into place.

Can you explain why?
Does the existing oil get pulled out in the evac process?
<-- Still learning about a/c. Thanks.

Jim, Thanks for the reply. I will go to Autozone and buy for one day their two stage vacuum pump. They have a policy that if you buy it, you can return it, in other words, it is a free rental. I did use a one stage pump and I left it evacuating for 3 hours, closed off the vacuum before removing it. I will wait and replace the expansion valve when I get it from Pelican. Still not sure why the wrong Valve was sent, weird. Steve

To remove the water from the system; 911 systems have a lot of internal surface area that water is attached. Low pressure is required to boil off and mobilize the water so it can be pumped out. The higher the temperature the higher the pressure this will start to occur. This phenomena occurs at low pressure levels that the Bourdon tube mechanical gauges used by DIY persons can't measure so to better ensure it is happening leave the system evacuating for long times.

A combination of the low vapor pressure of the oil and the placement of charging ports minimizes the loss of the system refrigerant oil during evacuation.

"I will go to Autozone and buy for one day their two stage vacuum pump."

If this is one of the "loaner" pumps, buy some new, fresh vacuum pump oil and replace the oil.

JIm, good idea, I have a 24 ounces, should be enough. Steve

No sweat. I was a grumpy bast*rd yesterday. Sinus on top of allergies. My apologies.

Sounds like things are underway.

The A/C will operate at the most efficient cabin cooling level running with the LOWEST blower setting that does not result in the compressor clutch cycling off to prevent freeze-up. Keeps the evaporator at the COLDEST possible temperature. Mine has an indicator light on the A/C control "panel" that is only on when the clutch is engaged.

Lowest setting also results in best human comfort.