Automotive Air Conditioning Information Forum (Archives)

BG1 on Tue July 20, 2010 10:07 AM

Year: 1990
Make: Chevy
Model: 1/2 ton pick-up
Engine Size: 5.7
Refrigerant Type: r134a
Country of Origin: United States

Is there an adjustment to make when changing over to R134A on a 1990 Chevy truck? I have read that on some there is one that will help make it cool better. Where is it adjusted and how much?

chris142 on Tue July 20, 2010 8:46 PM

I use a yellow orifice tube instead of the stock black one.

CCWKen on Tue July 20, 2010 11:11 PM

Yellow? What size is that?

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Ken Kopsky

Custom Car Works
"Rules are for the guidance of wise men and the obedience of fools."

chris142 on Tue July 20, 2010 11:15 PM

.062 I think.

CCWKen on Tue July 20, 2010 11:19 PM

Ops. Yeah, I found it. .062" is correct. Thanks.

-------------------------
Ken Kopsky

Custom Car Works
"Rules are for the guidance of wise men and the obedience of fools."

BG1 on Wed July 21, 2010 12:30 AM

Is using the yellow orifice the only thing needed to be changed? What does using the yellow one do for it? I thought I had seen where someone mentioned a blue one that is for Fords but I do not remember why.

bohica2xo on Wed July 21, 2010 11:55 AM

Ford Blue is .067 diameter. Ford Red is .062 diameter.

Some people prefer to run the slightly larger blue orifice, especially when retrofitting a GM product that had a white tube.

Any 134a conversion is an experiment. You may wind up changing tubes until you get the performance you think you should have, since the system was never designed for that refrigerant.

The "adjustment" you have been hearing about is the cycling pressure. The cycling switch on CCOT systems needs to be adjusted for 134a, because it has a different P/T curve.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

BG1 on Wed July 21, 2010 7:56 PM

Does anyone know of a part number or the year and make of vehicle the yellow is used on? How is the yellow better than the black? I know some of this is trial and error but if someone has this figured out I do not mind if it helps me out.
I am working on a 1990 Chevy truck and also need to work on my 1976 Pontiac Firebird, I have seen where blue and yellow orifice tubes have been recommended so which color should I use?? Thanks

Edited: Wed July 21, 2010 at 8:49 PM by BG1

BG1 on Fri July 23, 2010 12:25 PM

My truck has the black orifice tube and I want it to cool better, which color orifice tube is going to be the better one to go with.