Model: Grand National
Engine Size: 3.8 tur
Refrigerant Type: 134a conver
Ambient Temp: 88
Pressure Low: 35
Pressure High: 250
Country of Origin: United States
I decided to get my a/c operational again after being down with a compressor failure for 5 years. My orifice tube was covered with garbage so I knew the entire system needed cleaning. I removed every component and flushed them numerous times until I got no debris coming out. I reassembled with new compressor, accumulator, orifice tube, seals everywhere and added 8oz of ester oil prior to starting the system. I cycled the compressor by hand at least 10 revolutions to circulate to new oil. I drew the system down to 30" Hg for and hour and let it sit overnight. It held perfectly. the next day it was 88*F and I began adding 134a after jumpering the pressure switch. Each time I added a can, I was careful to purge the lines of air before adding the freon. Around can #3 the line after the orifice tube going into the evaporator began frosting heavily. I gave up not long after with the low side at 35 and high at 250. At no time did I every start seeing a hint of cold air out the dash vents. They remained at a constant 100* the entire time. I am going to review the factory manuals today to understand how the ducts and passages are actuated, but I'm feeling like my issue is at the orifice tube. Would a blockage completely prevent any cold air from coming out the vents?? Any insight is appreciated.
Was evaporator flushed while still in car? If so, how do you know the flushing agent is completely out of it?
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
The evaporator was removed from the car and flushed multiple times until particles were gone, then blown out with compressed air.
Your pressures do not indicate OT blockage, they look good. I think it is in the blend door and or heater controls. You can block off (pinch off w/ vice grips) one of the heater hoses and see if vent temps drop.
I was surprised today driving the car home from a car show. It was 91*F outside and pretty hot in the car, I had the windows down and wanted to get some air thru the vents. For the heck of it I selected Normal AC. I was astonished when cold air started coming out the vents! It actually read 70* at the vent. I didn't run it long since I knew I didn't have a full charge of 134a. So why did I not get ANY cold air the other day and now I have working a/c? BTW, they was no frosting of the line after the orifice tube today.
Better air flow over the factory tube and fin condenser.
? what did you use to flush your system? I have a locked up comp that I am considering DIY but don't have a flush system
I continued to add freon to the system and drove the car again. At 92*F I got 36 on the low side and 260 on the high side. My vent temps got down to 40* while driving. I was certainly comfortable and an improvement, but I am hoping I can get it lower. At this point, I have added about three cans total of 134a. What if any cautions should I be concerned with at this point? Where is a safe stopping point as far as adding freon?
a safe stopping point is to measure the in and out tubes of the evap. Should be close to the samr temps.
Hi Tim; For a car that was converted, those(40 degree) temps @92 ambient outside air are incredible! My advice(and others here I'm sure will agree) enjoy it as is, don't push it further,you have done well!!
Edited: Sun June 13, 2010 at 9:58 PM by fonebone
This is a Ã¢ÂÂGÃ¢ÂÂ body car and has two vacuum lines the feed into the cab of the car. One is a grey or black for main vacuum and the other may appear to be a pink that feeds to the hot water shut off valve. Make sure that these are in good working order, Also since you did a 134a conversion did you switch or adjust the low pressure cycling switch? The OEM condenser is a 10mm tube-n-fin style that will need extra cooling by adding an electric fan or changing to a PFC.
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