Automotive Air Conditioning Information Forum (Archives)

sjrider on Wed July 21, 2010 11:15 PM

Year: 1993
Make: bmw
Model: 318i
Engine Size: 4 cyl
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 27
Pressure High: 175
Country of Origin: United States

1993 bmw 318i, Just got the car with 135,000 miles and 10 psi on the low side. Sight glass showed no dye in the system. Pulled a vacuum for 1 hour, it held for 30 minutes so I gave it two 12 oz. cans of 134a. At the end of the second can I had 30 deg. at the vents, 85 deg. temp. here now 27 lbs. low side and 175 on the high side at 1500 rpm. The car is supposed to take a little less than three 12 oz. cans. With a vent temp. like that I stopped after the 2nd can, whats up with that?

HECAT on Wed July 21, 2010 11:23 PM

You can actually achieve cool vent temps in certain conditions with a 25-50% undercharge. But you will not achieve proper lubricant migration through the loop. You are starving the compressor for oil. Make sure you put the full charge in.

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sjrider on Wed July 21, 2010 11:29 PM

Thanks for the reply, I'll add the 3rd can. However I did'nt add any oil, should I have?

HECAT on Thu July 22, 2010 7:15 AM

It may have a leak, the refrigerant went somewhere, although it passed a vacuum leak down test. Leaks can allow a little oil to escape, however it is usually minimal. You could add 1 oz to compensate, but that's just a WAG.

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Gordon Shumway on Sun July 25, 2010 11:38 AM

New guy here.
Specific volumes of refrigerant require specific volumes of oil to insure not only proper lubrication but also proper cooling. Excess oil hinders the atomization and condensation of the refrigerant. The only way to know exactly how much oil is in the system is to flush the system thoroughly and replenish with the proper amount and type of oil.

sjrider on Mon July 26, 2010 9:45 PM

Thanks for the help!!!! just found out that my temp. gauge is 10 deg. off it's really 40 deg. coming out the vents.