AC Recharge Help
07-23-2010, 04:01 PM
#1
Rennlist Member
Thread Starter
AC Recharge Help
My 1990 no longer blows cool air, and I'd like to top up the R-12. I have the R-12,
and a set of Robinair Guages. My understanding is that you warm up the car,keep it at 2000 R.p.m., AC on, temperature to Blue dot, fan on high. Hook up to the low side on the compressor. Does anyone know what pressure indicates that the Freon is low, and what pressure indicates full? There is no site gauge. so other than pressure,how do you know when it's full. I also have a 4oz.(113 gram) can of R-12/oil. Should this be added also? How much?
The total system holds 930 grams. I was thinking, that I would add 1 can (340 grams), and see if it starts to cool.
Any help from someone who's done this would be appreciated.
Thanks
and a set of Robinair Guages. My understanding is that you warm up the car,keep it at 2000 R.p.m., AC on, temperature to Blue dot, fan on high. Hook up to the low side on the compressor. Does anyone know what pressure indicates that the Freon is low, and what pressure indicates full? There is no site gauge. so other than pressure,how do you know when it's full. I also have a 4oz.(113 gram) can of R-12/oil. Should this be added also? How much?
The total system holds 930 grams. I was thinking, that I would add 1 can (340 grams), and see if it starts to cool.
Any help from someone who's done this would be appreciated.
Thanks
07-24-2010, 07:51 AM
#2
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Hi Steven,
If your AC is not cooling you may be short on refrigerant.
When the gauge manifold is connected to the refrigerant compressor ports, (Blue service hose to the low pressure suction side port-large tube) (red service hose to the high pressure side discharge port-small tube) and then the AC compressor engaged.
The low pressure blue gauge should indicate the pressure/temperature of the evaporator coil and the red gauge will indicate pressure/temperature of the condensor coil.
If the pressure is below zero kPa/Psi (atmosphere) on the blue gauge you have a problem in that the system is drawing in atmospheric air/moisture from the leak site and that there is little to no refrigerant in the system.
The leak site will sometimes be obvious by the small amount of oily/dirt residue generally found on fittings and joins.
If the system pressure is below atmosphere you must find the leak site and repair the problem, could be simple... loose compression fitting, could be bad... hole in the condensor, compressor shaft seal, leak at the AX valve on the evaporator coil (this is the first part on the assembly line and the rest of the 911 is built around it
)
After repairing the leak site, pressure test the system with dry nitrogen and refrigerant and leak test with a sniffer.
Replace the refrigerant liquid receiver/drier before going any further, then evacuate the refrigerant circuit with a evacuation pump before adding refrigerant. Evacuation is very important, do not refill without evacuation!
There should'nt be a need to refill with oil unless you can physically see a large amount of leaked oil.
If the suction pressure is above atmosphere when the engine is running and the compressor is engaged then the leak is probably smaller and topping the system up will improve the cooling.
A good sign that the refrigerant charge is fine is that the larger tube on the compressor is sweating after a few moments of operation. You could probably aim for about 5 - 10 dgrees C on the gauge when topping up the system.
Remember to operate the AC system with the recirculation button activated.
Hope this helps...
If your AC is not cooling you may be short on refrigerant.
When the gauge manifold is connected to the refrigerant compressor ports, (Blue service hose to the low pressure suction side port-large tube) (red service hose to the high pressure side discharge port-small tube) and then the AC compressor engaged.
The low pressure blue gauge should indicate the pressure/temperature of the evaporator coil and the red gauge will indicate pressure/temperature of the condensor coil.
If the pressure is below zero kPa/Psi (atmosphere) on the blue gauge you have a problem in that the system is drawing in atmospheric air/moisture from the leak site and that there is little to no refrigerant in the system.
The leak site will sometimes be obvious by the small amount of oily/dirt residue generally found on fittings and joins.
If the system pressure is below atmosphere you must find the leak site and repair the problem, could be simple... loose compression fitting, could be bad... hole in the condensor, compressor shaft seal, leak at the AX valve on the evaporator coil (this is the first part on the assembly line and the rest of the 911 is built around it
) After repairing the leak site, pressure test the system with dry nitrogen and refrigerant and leak test with a sniffer.
Replace the refrigerant liquid receiver/drier before going any further, then evacuate the refrigerant circuit with a evacuation pump before adding refrigerant. Evacuation is very important, do not refill without evacuation!
There should'nt be a need to refill with oil unless you can physically see a large amount of leaked oil.
If the suction pressure is above atmosphere when the engine is running and the compressor is engaged then the leak is probably smaller and topping the system up will improve the cooling.
A good sign that the refrigerant charge is fine is that the larger tube on the compressor is sweating after a few moments of operation. You could probably aim for about 5 - 10 dgrees C on the gauge when topping up the system.
Remember to operate the AC system with the recirculation button activated.
Hope this helps...
07-26-2010, 06:27 AM
#4
Rennlist Member
Thread Starter
Thanks for the info. Frank964.
mojorizing, I pulled the driver's side front wheel and inner liner, but could not find the site glass.
Is it obvious? Do you have a pic?
Thanks
mojorizing, I pulled the driver's side front wheel and inner liner, but could not find the site glass.
Is it obvious? Do you have a pic?
Thanks
07-26-2010, 08:19 AM
#5
Burning Brakes
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My OE bare aluminum drier had a site glass, the aftermarket black one that replaced it did not. When I had a chemical engineer buddy of mine help me refill my system with R12 about 10 years ago he brought out text books with AC curve charts, made note of the air temperature and humidity and tried to teach me about terms like dew point, things way above my head. The system still blows cold but I wonder if just monitoring the vent temperature for a minimum value, while adding R12 would have worked.
Bill
Bill
07-26-2010, 01:20 PM
#6
Rennlist Member
Sight glass isn't obvious. It's integral to the dryer, at the top where the tubing connections are located.
There are pressure/temp charts that give you a range on the correct amount of refrigerant in the system.
There are pressure/temp charts that give you a range on the correct amount of refrigerant in the system.
07-30-2010, 10:37 AM
#7
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Thread Starter
Thanks to those here and on Pelican who provided me with information about undercharging my AC.
Basically, I just charged until I got a low side pressure of 30-35 PSI, and a high side pressure of around 140 psi. System was around 1/2 full. Now blowing very cold air.
Basically, I just charged until I got a low side pressure of 30-35 PSI, and a high side pressure of around 140 psi. System was around 1/2 full. Now blowing very cold air.
