Automotive Air Conditioning Information Forum (Archives)

79vetter on Wed July 20, 2011 3:25 PM

Year: 1979
Make: Chevy
Model: Corvette
Engine Size: 350
Refrigerant Type: R12
Ambient Temp: 96
Pressure Low: 47
Pressure High: 49
Country of Origin: United States

I finally charged with 48 Oz of R12 Underneath Shaded Carport - 96Deg. Ambient Temp.

Static Pressures 98-Low 100- High
At Idle - A/C on Max High 47-Low 49- High
@1500Rpm 35-Low 45-High

Vent temp with doors and Windows closed: 54 Degrees

Questions:

I was expecting something like 40Degrees Vent temp., not 53 (at 1500rpm)
Why is my High Side so Low? My A/C belt is a little loose and needs tightening.

... My Accumulator feels cold - as well as the line to the Compressor (which is new).
Any advice is appreciated.

Rob

Edited: Wed July 20, 2011 at 3:55 PM by 79vetter

HECAT on Wed July 20, 2011 3:55 PM

No OT?

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TRB on Wed July 20, 2011 3:57 PM

I was tihink the same thing.

Karl call me.

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79vetter on Wed July 20, 2011 4:50 PM

Yes - there is an Orifice tube installed

spongebob on Wed July 20, 2011 6:00 PM

where would a OT go?? and without it the high side wouldnt be low...would it?

79vetter on Wed July 20, 2011 8:29 PM

Anyone else have some advice?

TRB on Wed July 20, 2011 9:34 PM

So it was installed the proper direction?

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79vetter on Wed July 20, 2011 9:49 PM

Yes- pretty sure. It just pushes down into the Evap tube - until it seats correct? I'm aware that one end specifically goes down first.
Let's say that this is Ok - what are some other possibilities for such a low High side pressure?

Edited: Wed July 20, 2011 at 10:13 PM by 79vetter

bohica2xo on Wed July 20, 2011 10:17 PM

I don't see how it is possible to have a high side pressure below the static pressure with 48 ounces in the system. In fact, the static number looks low for that ambient when you add underhood heat.

I would suspect a hose / coupling / check valve / schrader issue. Or simply a bad high side gauge. Try a different gauge set if you can.

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.

spongebob on Wed July 20, 2011 11:05 PM

try the low side on the high side to see if the gauge is Ok!

not that it matters but is it a L-48 or L-82??

Edited: Wed July 20, 2011 at 11:06 PM by spongebob

JJM on Thu July 21, 2011 12:43 AM

I agree too that the static pressure does appear too low for ambient, which leads me to believe the gauges are no good, or the R-12 is suspect. Where was the R-12 sourced from?

Is the system all stock? Did the OT go in very easily, or was it snug? What kind of OT did you use?

Was the system plumbed properly?

Any frosting on the high side, including the condenser? Do you have an IR thermometer or thermocouple to measure the condenser inlet and outlet temperatures?

Joe

79vetter on Thu July 21, 2011 7:24 PM

Sorry Guys, I had a high side port hidden under the fender lip. Here are my new results with it now connected:

Ambient: 103
Static: Low- 98 High 100
Idle: Low -42 High 240
@1500rpm Low 30 High 250

Still getting vent temps in the 60s. Any thoughts?

thanks

Edited: Thu July 21, 2011 at 7:29 PM by 79vetter

bohica2xo on Thu July 21, 2011 8:34 PM

Looks like a blend door issue or re-heating.

Refrigerant loop pressures are good for that ambient.

-------------------------
"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.

JJM on Fri July 22, 2011 12:54 AM

Yup, clamp off the heater hoses for 15 minutes and see if vent temps improve. If they do, you found your problem.

Also, is the evaporator inlet and outlet temperatures the same, or the outlet slightly colder than the inlet?

Joe