79vetter

New Compressor, Evaporator, Accumulaltor, Flushed condenser, New Main Line, O-Rings and Orifice. Vacummed 3 hours and held vacuum fine. Oil and dye added. Compressor rotated.

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: 47-Low 40- High
@1500 Rpm 35-Low 45-High

Vent temp with doors and Windows closed: 54 Degrees

Questions:

I was expecting something like 40 Degrees Vent temp., not 53 (at 1500rpm)
Why is my High Side so Low? I did install the orifice.

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

Paul L

I don't have an answer to your question but I am curious. What led you to expect 40*F at the dash vents with an ambient temp of 96*F? I have read that a 25-35* differential is normal. But you may have other sources.

'75

Are you sure you don't have both gauges on the low side? Those pressures don't make sense. Also there should be a site glass on the right fender near the pressure switch. Are you seeing bubbles when the system is on and stable?

79vetter

My '79 doesn't have a sight glass..I am assuming that the high side port is on the hose manifold at the compressor.

'75

This should be the port for the hi side
http://www.zip-corvette.com/ProductD...GR-SR&CTitle=&

Or this one depending on earl or late
http://www.zip-corvette.com/ProductD...GR-SR&CTitle=&

my 76 ray

The charts that came with my gauges say the low pressure should be 50-55 psi at 95 degrees ambient and the high side should be 275-300 psi. These are general guidelines and you should follow the manufacturers specs if you have them. Then there is another chart that says that if both the low and high sides have pressures lower than the spec, you need to add refrigerant.

OOPS. I just realized you have R12. The above applies to R134A.

TimAT

Is the orifice tube in the correct direction? Just asking. It can be installed backwards.

AzMotorhead

If you can take a pic & show us how you have the gauges hooked up.
I'm betting you have 2 low pressure ports

mds3013

'75 has he correct pic. for the high side port. Your high side port will be a smaller diameter than the low side port. You will need an adapter to hook a standard size hose to it. There are two low side ports on your car, one at the back of the compressor and one on the dryer. The sight glass on my '77 is very small and is next to the high side port. Your '79 may not have one. mike...

79vetter

I saw that port underneath the fender lip but I didn't know that is the high side port. My main hose has a port on the manifold where it connects to the back of the compressor...Perhaps that is just another Low side port?

mds3013

As far as air temps. do this. Drive car in the early morning before the sun heats everything up. Take outside ambient temp. while driving. Then turn on "Vent" full cold and note temp. at center grills, again while driving. Note delta T/differance in two temps. This will tell you if your heater shut off valve is closing off water flow through heater core. I run a manual shut off valve as my vac. valve will leak through about 10* of temp. rise. Then turn on A/C, ck. temp. on normal setting and temp. on "MAX" setting again at center grills. This will tell the guys how the system is performing. mike...

79vetter

Thanks for the pics and replies. I'll get ahold of an adapter and re-check those pressures.
I too run with a man. shutoff valve to the heater core.

centralcalvette

Something is up with your pressures, Hi side should be much higher, low side could be a little lower, vent temps ??? depends on other issues, may be ok, could be a little lower. Heater shut off, how is your fan? condensor CLEAN, did you evacuate the system with a vacuum pump before charging? Did you get any air in the system (purge charge lines ?) Do you have a max or recirculate setting ? Prev poster is correct, ac will only cool approx 30F, 95F ambient air, coming over your 200f hood gets the air hot just to start, that's why we have recirc.

oldboat

Check that the hand valve on the high side pressure gage is closed.

noonie

All factory r12 systems came with a sight glass. You wouldn't be the first to miss it.
Sounds like you're a very little shy of refrigerant, but very close.
Measure your outlet evaporator pipe temp at the housing, should be in the low 30's and cold and sweating all the way to the compressor.
If you get connected on the high side you should be seeing pressures just below 200 @ 95°

79vetter

Since my A/C Gauge set has the R134 quick disconnect attachments, can I just screw on a r134 retro fitting onto the high side port - and then just use the quick-disconnect fitting ?

noonie

If you have a 134 gauge set then use the adapters on the original fittings.
High side gets the red 16mm adapter, low side the blue 13mm
Make sure they are correct.