Air Conditioning

[michael Sciarra]

Maybe someone knows a bit about this subject - just went through the archives and could not relaly find the information I need. Here goes. I have a 72 with air ( is is probably not the factory compressor). The unit is a radial type about 8 " in diamter and 4 or so in width. The system worked poorly since I bought the car about 5 years ago, but it DID WORK. It would loose the charge in about a year and a half. Last month I tore out the blower fan and motor and replaced the motor but not before I cleaned the evaporator core of about 20 years of crud. Inspected my work with a bore scope and sealed her up. Fan velocity increased to 15 MPH from 8.

Also, all baffles work properly and no heat comes out any vents if the system is on Air Conditioning modes.

Off to the garage: Had them replace the dehydrator, Sucked down to 28 mmhg for 40 minutes, and shoved 2.2 pounds of R12, leak detect, and compressor oil into her.

Result: No good. The POA valve gets a good amount of frost on it as does the cpaillary oil tube coming out of it. The lines do not feel cold going into or out of the evaporator. Ok, the input seems 'chilly'. In any event the cooling is minimum. My question is, How much does the system require in pounds? IE: is it 3#s? And, if you only put in 2.2 ( as they insisted) would this cause almost no cooling? I am no expert. I did however install (including the right fender diverter - built that with mirrors - never really did see 'it' !) a factory air conditioning system in a 72 with no air about 25 years ago. I also remember replacing the POA valve.... Any help would be apreciated. michael sciarra

[Jack H.]

Re: Air Conditioning

(1) Original fill for your car's system was 3.25 lb of R12.

(2) But, this was with the factory original A-6 compressor vs. the R-4 compressor you have. Might be a minor difference due to the specific cylinder capacity of the R-4.

(3) You should be able to tell when the system's full by using the sight glass on the receiver/dryer (presuming you haven't replaced it with one of the modern, 'improved' dryers without a sight glass). If you have, you'll have to go from the Chassis Service manual's table for high side/low side system pressure.

(4) The POA should NOT be frosting over! It should get cold to the touch, but then regulate refigerant flow through the system to throttle back and thwart evaporator freeze-up.

[michael Sciarra]

air conditioning

Thank you Jack for the information. - spoke to the owner of AC specialties ( in my area) and he said basically the same thing and yes, I replaced the dehydrator with an 'improved version' - no sight glass AND, woe is me, there is no high side schrader!. But I do know exactly how much the other shop has already put in - 2.2 pounds.

He also said the POA can freeze up if there is not enough pressure in the system to let it open up wide to begin with so although he makes no promises, he believes the thing will open when the right amount of charge is in - do you agree with this thinking? best regards, michael sciarra

[Jim T.]

Re: Air Conditioning

Michael there is a small screen in system that could be stopped up. Your system will have to have the R12 evacuated to open the system and clean or replace the screen in the valve. It is very easy to do by disconnecting a line and removing the screen. New ones used to be available at a well stocked parts stores. This procedure is listed in the service manual.