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Username Post: Frost on A/C lines        (Topic#345488)
68Cam 
Member
Posts: 51

Loc: Des Moines, IA
Reg: 05-29-04
06-17-17 08:24 PM - Post#2696304    

I have 72 Chevelle all orig A/C sys including the R12. Expansion & POA valves. I cleaned the inlet screen to the Exp vlv, flushed the line from the Receiver Drier to the Exp Vlv, Replaced the Rec/Dri
& added 1 oz min oil to it. Evacuated for 1 1/2 hrs, charged with 3.75 lbs of R12. Now the Exp vlv, the line entering the Evap, & the small oil line exiting the Evap are all frosted over & no cool air at the vents. Static pressure after charging, but before starting system = 104 lbs. both sides.
While sys is running: Lo = 17 lbs, Hi= 115 lbs.
Any idea what the problem is? Thanks



 
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bobb 
Super Senior Member
Posts: 5308
bobb
Loc: paradise
Reg: 09-05-03
06-19-17 09:59 PM - Post#2696671    
    In response to 68Cam

blend door?

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
68Cam 
Member
Posts: 51

Loc: Des Moines, IA
Reg: 05-29-04
06-20-17 09:58 AM - Post#2696751    
    In response to bobb

Thank You for your reply. I appreciate both of your suggestions. 1. I have prayed about it. 2. The blend doors definitely have a problem, but in the past, my recollection is that the cold air just blew out of the floor vent instead of the dash vents. This is frosting up & blowing ambient air, within seconds after starting the engine, before the engine has time to heat up the coolant. The expansion valve was not clogged when I had it off, but I'm going to check it again. I'm leaning toward a restriction in the Evaporator (which I'm going to check) or the wrong shrader valve in the POA. I went to an Air Cond class taught by an expert named Dennis Husband, who was flown from Texas to Des Moines, IA to teach on A/C. He said It's important to have a shrader valve that releases at 9 lbs pressure in the POA. I have not been able to find pressure specs on shrader valves though. My old AC Delco A/C parts book says that part # 15-513 is for the POA & another parts book says 15-1119 is for a drier (which would not apply to a 72 Chevelle, because there is no port on the drier) When I try to buy 15-513, I'm told that it is obsolete & 15-1119 is the new #. Can anyone clarify specs on valve cores? Various part #s look the same, but there must be differences about them? Thanks for any help!



 
68Cam 
Member
Posts: 51

Loc: Des Moines, IA
Reg: 05-29-04
06-25-17 01:16 PM - Post#2697437    
    In response to 68Cam

Success at last. When I disassembled the a/c sys again, I found that a small amount of new desiccant mud was in the inlet screen to the Exp Valve. Even though I could blow through this without any restriction, I think this was the problem. Even though I had flushed the line from the Cond to the Exp vlv the 1st time, I did it again & back flushed the Condenser. The flush fluid from the Cond was dirty, but no debris came out. I also blew back on the Evap - nothing came out. Even though the sys was only run about 5 min the 1st time, the sys was open for a while working on it the 2nd time, so I ordered another new Receiver - Drier. I added an ounce of oil to the cond, rec-dri, evap & 2 oz to the compressor (because I could not get a dip stick wet). Now there are not frosted lines, the air is very cold & the pressures look better. I still can not find 3 parts: 1. The screen in the Exp Vlv (orig AC Delco # 15-512 (so I've cleaned out the orig one & re-used it. 2. The low tension valve core or (shrader valve) AC Delco # 15-513 that screws into the POA where the oil line from the Evap connects (so I reused it too, because it's tension was much weaker than the 15-1119 that is suppose to replace it). 3. The O rings that fit in 2 places in the POA. One is on the oil line mentioned in No. 2 above, the other is the line that comes from the Exp vlv. The orig AC Delco # is 15-3153 & the GM # is 12307177. Here again, I am given a NAPA replacement # of 407204, but the diameter of this rubber is too thick. When I installed one, it cut it. The 15-3153 has 3/64" thick rubber and Napa's 407204 has 1/16" thick Green rubber. Hope this helps others. If anybody comes up with parts solutions on these 3 parts, please share. Thanks for the forum.



 
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