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Topic: How much 134a in a 79?

in Forum: C3 Cooling and Heating Systems

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How much 134a in a 79? (1/4)
5/30/08 4:32pm

neuroclast
Former Member
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Charleston AFB, SC - USA

Vette(s):
1979 Cream Beige Coupe w/383 & 700R4

Joined: 10/31/2007
Posts: 111

I just finally got my AC installed. Took a lot of work and near $600 total, but it's working. I'm getting ~60 out of the vents though which isn't making me happy. It's also not blowing very hard.

My main question is how much 134a should be in the system? The guys at the shop put 2.5 lbs in, but I really have no idea how much should be in there. Do I need more or less?

On another note, I have heard mention of a blower motor upgrade which supposedly helps out our weak one. Any suggestions on that?

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How much 134a in a 79? (2/4)
5/30/08 5:07pm

my7t1

Lifetime Member
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Dorr, MI - USA

Vette(s):
71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp

Joined: 8/21/2002
Posts: 2581

I don't have a chart handy as to how much R12 yours takes (I'm guessing around 3 lbs.). But if you can find that amount, the formula is

R12 X.9 - .125. In other words 3 lbs. of R12, would be 2.57 134A. Now I feel you have enough to get the system cold. Are your lines cold going into evaporator? If not you have an issue with the under hood plumbing. If so you have an issue with possibly mixing warm air with cold, which is a blend door or control valve problem. I would make sure your control valve is cutting off warm coolant from going through heater. A lot of guy's will put in a manual valve. I'm not sure about blower motor upgrade. If your blowing air out at all It should be well below 60 deg. 40 good 45 acceptable.

______________

Click on images for Before and After pics!

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How much 134a in a 79? (3/4)
5/30/08 5:32pm

neuroclast
Former Member
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Charleston AFB, SC - USA

Vette(s):
1979 Cream Beige Coupe w/383 & 700R4

Joined: 10/31/2007
Posts: 111

Yeah the lines are cold going in. Everything appears to be working, just the air only gets to 60* :\

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How much 134a in a 79? (4/4)
5/30/08 6:21pm

my7t1

Lifetime Member
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Dorr, MI - USA

Vette(s):
71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp

Joined: 8/21/2002
Posts: 2581

I would check your hoses going in and out of your heater. If there's not a difference in temp before and after your control valve, it may be stuck open.

______________

Click on images for Before and After pics!

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