I have an 86 Camaro and have replaced every part of my A/C system with NEW parts except for a rebuilt compressor. The vent temps are are 80 degrees and both high and low side pressures are high. Trying to diagnose I have checked and replaced the orifice tube a couple of times 1 white and 1 blue one. The blue tube gave about 5 psi lower pressures. I blew through all the parts with 134a and didn't find a restriction. I felt like the system might have uncompressible stuff inside like water/air since both pressures were high so I replaced the dryer and orifice tube again and got the same results.
Here are my specs.

Label says 2.25 lbs R12 -- I added 80% of 134a 28ozs.
8 ozs PAG 150
Vacuumed for 30 min at 29 mmhg
Heater hose pinched off.

750 RPM
Low side pressure 48 psi
High side pressure 260 psi
Evaporator exit temp 63 degrees
Condenser inlet temp 130 degrees
Condenser outlet temp 103 degrees
Vent temp 80 degrees

1250 RPM
Low side pressure 34 degrees
High side pressure 305 degrees
Vent temp 75 degrees

1250 RPM Wetted down the condenser
Low side pressure 30 psi
High side pressure 205 psi
Vent temp 90 degrees

Any suggestions would be greatly appreciated. I have been working on this for a week and am about ready to take it to someone else.

 

You should have good cooling with those pressures, IF the capacity is correct. I recall the original capacity in this era being around 3.25lbs.

The pressure drop with water is to be expected, particularly if the fan clutch is not excellent when running 134a.

 

We have 2 86 Camaro's and they both say 2.25 lbs of R12. Less refrigerant had no better cooling and more resulted in even higher pressures.
I forgot to mention that I have an electric fan and a new radiator also.
The ambient air temp was 80 degrees.

 

I'm out of ideas then. I did not realize any N.A. designed GM product had a capacity that small in that era.

 

Did you adjust the on/off low pressure cycle switch down a few lbs..? there is a flat head screw u turn to do this. if i remember correctly, r12 is factory set at 25lbs and r134 works best around 21lbs, switch is on side of dryer, pop cover, turn screw counterclockwise approx 1/4 turn.. check with gauges



I used the ford blue orifice tube when I converted my '86..

 

 

hell, I would just vent the 134a until the pressure switch activates.. I remember having to let some out when I did mine.. otherwise ?????

 

Bypass the heater core temporarily to make sure your cold air isn't miking with the heater core, can you hear the blend door close? Also adjust the low pressure counterclockise further not to exceed 3 turns, are your radiator fans coming on when the A/C is switched on?

 

I have pinched off the heater hose to eliminate that possibility. The low pressure switch was adjusted to 22 psi years ago when I converted to 134a.
An instant read thermometer was much more accurate and stable for temperature measurements.
I am 100% sure the orifice tube is in the correct direction and there is only one. This last time in installed a variable orifice tube.
Re-circulation door was not opening to the recirculation position. It is now open and the vent temp has dropped to 50 degrees.

Here are the new conditions:

Across the front of the condenser the temp was 142 on one side and 120 on the other.

Ran for 10 min.
Ambient air temp 74
Inside car temp 74


1250 RPM
low side pressure 28 psi
high side pressure 260 psi
evaporator tube in temp 38 degrees
evaporator tube out temp 36 degrees
condenser tube in temp 192 degrees
condenser tube out temp 120 degrees

I know it is cooler today and getting the recirculation door open made a big change. I still feel like the pressures are too high and the inside temp is not low enough. I think I will try to adjust the refrigerant level down first and see if I get any major change.
Thank you all for your help,
Steve

 

I worked on a system in a TPI swapped 1987 Firebird just yesterday in 95*F ambient temps with 41% humidity. Dual LT1 cooling fans screaming. Car has a large transmission cooler mounted in front of the condenser. The car has a LT4 Hotcam and idle is 950 rpm in Park/Neutral, 800 rpm in drive. I charged with R152A using a factory white orifice tube. Low side pressure stayed around 35-40 psi at idle. High side was 230 psi. Vent temps hit 40*F at idle. Cycling switch is adjusted to cutout at 24 psi right as the evaporator and accumulator start to frost over. At 2,000 rpm, the low side pressure drops low enough to cycle the clutch approximately every 20-30 seconds. High side pressure leveled off at 260 psi. At idle the compressor discharge was 160*F, the condenser outlet 110*F, the evaporator outlet and accumulator outlet 35*F. Accumulator was insulated with a GM accumulator blanket from a newer truck. The suction side line is also insulated with foam plumbing insulation. Insulating the suction side makes a big difference in head pressure readings by keeping engine compartment heat out of the cold side of the system. I took the car for a drive after charging the system and after a few miles you could practically hang meat inside it.

 

What kind of cooling fan do you have electric or clutch?
What does the low side line or the drier feel like when it is on?they should be cold and sweating.

 

Your pressures look pretty much in the ballpark. Probably not a refrigeration system problem as such.

You have some sort of air control door malfunction, or that sort of thing.

I'd be looking at the evap housing if it was mine, where it goes above the exhaust manifold. With age and heat, that material turns to dark brown burnt-looking dust and just crumbles. When I pulled that piece off my my 83 back in the 90s, it already had a hole in it about half the size of the evap itself in it where the old stuff had disappeared and fallen out. Fixed it with fiberglass. Wouldn't hurt to rivet some sort of heat shield over it, just sheet aluminum or something, with a small gap between the hosuing and the exhaust.