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ac still not blowing cold

blasterx2g on Fri November 30, 2007 12:30 PM User is offlineView users profile

Year: 1972
Make: chevy
Model: mailbu
Engine Size: 307
Refrigerant Type: r12
Ambient Temp: 90
Pressure Low: 32
Pressure High: 80
Country of Origin: United States

Its been months and i still cant get my ac on my 72 chevelle to blow that cold. High and low temps seem ok. The evaporator is sweating and the POA seems to be opening at the rpm that it should. Its blowing 80 air out of the vents and the front of the poa is barely cool. It has the proper oil and freon and most everything is new or rebuilt. Any more ideas on what i should do?

blasterx2g on Fri November 30, 2007 12:32 PM User is offlineView users profile

Sorry...low is around 32 and high is around 180

Dougflas on Fri November 30, 2007 3:19 PM User is offline

with the engine rpm at 1200 to 1500, what are the readings? Is the sight glass clear with no bubbles? Unplug the blower motor and does the low side stay around 30 lbs? Have you clamped off the heater hoses and measured the right hand duct temp? Make sure you have an external fan blowing in front of the grill to get airflow across the condenser.

You may be low on charge as the POA is trying to regulate the low side. I like to see 210 to 225 on the hi side at 90º ambient.
Don't forget that an older vehicle may need to have its ducts/seals replaced...you may be leaking air around the dirverter doors.

Edited: Fri November 30, 2007 at 3:22 PM by Dougflas

NickD on Fri November 30, 2007 4:30 PM User is offline

Besides testing at 1,500 rpm, also nice to know the evaporator inlet and outlet temperatures.

blasterx2g on Fri November 30, 2007 10:26 PM User is offlineView users profile

Almost no bubbles are present. The exact amount (3.75 lbs) are in the system. Ive clamped the heater hoses off. Ducts/seals seem fine. he car is 100% original and been garaged. Have unplugged the blower. As i recall the evaporator starts to freeze up. Evap temps were taken and seem fine.

Dougflas on Sat December 01, 2007 5:40 AM User is offline

when you unplug the blower motor, what does the low side read?? Almost no bubbles is not good. Sight glass needs to be clear at this point. This will ensure you get a full stream into the TXV. I used to charge these systems until the glass showed no bubbles and then add another two oz of R12. This will let the receiver-drier do the other part of its job which is to store refrigerant.

Edited: Sat December 01, 2007 at 5:44 AM by Dougflas

blasterx2g on Sat December 01, 2007 10:33 AM User is offlineView users profile

The system holds 3.75. Wouldnt the system begin to start working with that much in? My other chevelle can be really low before it stops blowing cold. What should the low side read when the blower motor is unpluged? I cant recall what it was.

Dougflas on Sat December 01, 2007 1:33 PM User is offline

low side with blower unplugged with R12 refrigerant should read 28 to 32 with 30 being optimal at sea level.

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