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GTO a/c needs help

Applekrate on Mon June 09, 2008 1:05 AM User is offline

Year: '72
Make: Pontiac
Model: GTO
Engine Size: 455HO
Refrigerant Type: R 12
Pressure Low: 50
Pressure High: 125
Country of Origin: United States


Perhaps someone can advise me on my a/c.

'72 GTO with A 6 comp and r 12. Does not blow cold. Clutch engages, fan works. I do not think it is a heater interference problem.
Sight glass is clear.
At idle low side 50, high side 125. Raise from idle low goes to 30, high stays around 125.
We just put 2 cans of r 12 in it and it still does not blow cold or cool. I realized the system may want another can or so but, I didn't;t want to add any more if I have to open the system.
System seems to hold vacuum well.

Any ideas? Something with the POA or expansion valve perhaps?

Any help appreciated.

Steve in Maricopa, Az

Edited: Mon June 09, 2008 at 1:08 AM by Applekrate

Chick on Mon June 09, 2008 6:45 AM User is offlineView users profile

Was the system empty when you added the two cans? Are you using real R12? what is the outside temp where you are? If you started with an empty system, you need to pull a good vacuum first, charge the correct amount into the vacuum, Do you see any movement in the sightglass at all? Did you ever see movement? Did you change the drier?. Give as much "history" on the system as you can..Hope this helps.

Email: Chick


Freedoms just another word for nothing left to lose

Edited: Mon June 09, 2008 at 6:45 AM by Chick

Applekrate on Mon June 09, 2008 9:53 AM User is offline

Hi Chick-
This was worked on last night in Maricopa so I would guess outside temp at around 85-90.

Yes, system was empty and was pulled down with a vac machine and it held good vaccum.

Yes, real R 12
Did not change the dryer
Did not notice any movement in sight glass.

thank you,


Applekrate on Tue June 10, 2008 11:52 PM User is offline

Hi, I am still looking for any info if anyone has time to reply.....

thanks much,

Dougflas on Wed June 11, 2008 1:31 AM User is offline

You need a full charge to evaluate this system. Full charge is lbs. Your high side is low which should be apparent at the sightglass on the drier. To test the system POA, fill to required charge, run engine at 1200 to 1500 rpm, remove blower motor lead. The low side should hold at 30 PSI.

fonebone on Wed June 11, 2008 1:47 AM User is offline

Hi Applekrate; Sounds like you did everything OK. except- you did not add enough r-12. Your machine should have a label on the compressor or under the hood somewhere stating capacity in lbs. and ounces. Those old systems held over 3 lbs, plus of freon. If you only added 24 ounces, you are way undercharged, hence the poor cooling. Didn't you check before you started working on the system as to how much it held? With those low pressures you are nowhere near full. Keep adding freon slowly,giving it time to adjust pressures, until it's full. DO NOT exceed what the label calls for! Keep you rpm's just above idle to help pull in freon. Put a floor fan in front of the car to keep temps down on the condenser. When adding, watch your temp gage. If your fan clutch is weak, it will not "lock up" the fan as it should to pull in more air. Keep us posted as to results, OK?

Applekrate on Thu June 12, 2008 12:49 PM User is offline

I was exepecting 'some' cooling with 2 cans. no?
Ok, I'll take your advice....I bought 2 cans of R 12 yesterday. I'll put in another can and try it and get back. I wishI lived closer to the site host...I would take it to them for service. I may end up driving over there anyway.
It is nice of them to provide this message board.

Edited: Thu June 12, 2008 at 12:50 PM by Applekrate

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