Blown427conv

OK the results are in...low pressure is 30, high press is 75. Acording to the low side gauge it is right on ht elow side of good, the high side is very low though. The high side is way down around 30 with the compressor off, and goes up to 75 with it on. Think the low side stayed fairly consistant on or off. Compressor always runs, and fans do too. OK, what is the general consensus? I though of maybe adding a bit more freon, but waiting for the wisdom of this forumn to guide me.
PS: I did the flasher bypass with the cutting 1 wire and jumping onto the other and it works GREAT!!!!!!!!!!!!!!!! Only cost me about $12 and my turn signals finally work all of the time.

wildbadbill

for most cars (don't think vette is different) with the AC off you should have about 90-100psi on both sides.If it's on than the low drops to about 40's and the high should be around 200.From what you say you're way low on 134A bro.

rebelheart

You are low on freon bud!!!

Jetts4u2

The high side pressure should be way over 200 PSI, so your freon is low. Except, the low side pressure should not be anywhere near 30, the compressor cuts out at 20 PSI, so it should be disengaging the clutch frequently and you should see it. Add more freon and see what happens. My compressor went bad and my orifice tube was still clean, so I wouldn't change it until I knew I had a real problem.

bighank

Used a pair of needle nose vise grips to remove my orfice tube. It was very tight and I thought it would break trying to remove it.
What is the orfice tube remover? What does it look like?
I lubricaed the orfice tube on the new one with refirgerant oil before replacing it. BIGHANK

Blown427conv

Thanks, I'm going to add some freon today and cross my fingers. The compressor never cycles (runs continuously) and the low side gauge is in the blue where it says it should be, albeit right at the bottom. It was the high side reading very low that had me wondering. I'll charge it and post the results this afternoon.

jimcork1

[QUOTE=Blown427conv;1570733844]OK the results are in...low pressure is 30, high press is 75. Acording to the low side gauge it is right on ht elow side of good, the high side is very low though. The high side is way down around 30 with the compressor off, and goes up to 75 with it on. Think the low side stayed fairly consistant on or off. Compressor always runs, and fans do too. OK, what is the general consensus? I though of maybe adding a bit more freon, but waiting for the wisdom of this forumn to guide me.
QUOTE]

Your compressor has failed. (you said it was running full time turning) If it is running continuous and you have 30 psi on the suction with only 70 on the discharge your compressor needs replacing. The orifice tube is not the problem. You can add more freon if you choose and your suction pressure might go up to 34 or so but I doubt the discharge pressure exceeds 80 psi. (I would expect around 250 psi.)

There is an internal failure. Continued running might put more contamination in the system. I would recommend:

1. Replace the compressor with new compressor. ( I stay away from rebuilds due to high failure rate)

2. Replace the receiver dryer and orifice tube then flush the system with refrigerant flush solvent.

3. After flushing and you are sure it is clean replace the orifice tube and dryer (just do a search on ebay under auto parts for orifice tube tool). I highly recommend buying for about $30 the tool to pull the orifice tube. If you break the orifice tube off inside the line with needle nose pliers you will be

Best of luck in your decision.

Blown427conv

Ugh, I didn't want to hear that. What do you think the gauges would look like if the orifice tube were plugged? Do you think the suction would be low and the high side high? What about the POA valve? I saw one listed for this car on the Autozone website? I think it goes in the back of the compressor? Would a Z28 or Trans Am have the same compressor? I can't seem to get Corvette parts locally for some reason, they are non-stocked items here.

jimcork1

If the orifice tube were plugged there would be no flow of liquid freon and the pump/compressor would have very high pressure and possibly vent through the Pop off valve to protect blowing the hosed. I would expect pressures of 350 PSI or higher.

From what I have seen the Z28/TA don't use the same compressor but you could check. I have found a vet compressor NEW spectra Premium for $250 + shipping. Delco new is around $400.

I have only seen a POA valve on my son's 72 454 Corvette but not on a C5. There is a safety high pressure relief on the system though.

Blown427conv

I put nearly 1 full 12oz can of freon in the car and it now cools great. It wouldn't cool on the drivers side at first but I continued to cycle the heat and cool back and forth while waiting for it to get to the full position and now it is ok. It does not stay as cool on the drivers side as the passengers side when idling for a while but when I get moving again it cools right back down. Seems vacuum related to the engine but I'm not sure. When I installed the new engine I added a 4" length of vacuum line at the back of the manifold, but that should't make a difference. It cycles from defrost, to head, to feet, to combo fine. Any ideas on it not staying cool on the drivers side at idle?

rebelheart

Sounds like it may be still a bit low on freon.

byronhunter

I think rebelheart is correct.

bestvettever

Hi, good choice to try first blown427. Now that you have the equiptment, you need to follow the proper procedure to get the charge right. There were posts by plastifan about the proper charge levels that were excellant, and would put the system at optimum levels. In a nutshell you should strive for the following levels.
1, It is best to charge and check levels on the vette at 2000 rpm's, it can be done at 1000, or 1500 accurately, but you have to compensate for the lower rpms, with higher pressures. As the rpm's increase the low side will go lower, and the high side higher.
2, At 2000 rpm's with an 80% relative humidity, and ambient temp at 80 degrees, the low side should be 34psig, and the high side right around 250psig, this should yield at least 50 degrees or lower at the center duct with a thermometer.
If the temp is 90 degrees and the humidity is 80% the low side is 39psig, and the high around 310psig, this should yield 67 or lower at the center duct.
Humidity levels do make slight differences in the optimum read levels, as do temps. But if you get close to those numbers you will have an optimum system.
3, The proper way to make sure you have optimum levels is to evacuate the system, as you don't really know who worked on it before you, and might have let air or moisture, or even the wrong refrigerant in it. Then pull a vacumn of at least 29inches, for a few hours to dry it out, then recharge it being sure to add some proper oil. If it hasn't been disassembled, usually about 4 to 6 ounces of oil will be enough to protect the system. If you suspect a leak, which you should, because refrigerant doesn't wear out it leaks out, a bit of dye added will help you find it.
4, To answer your question about the difference in temps at the driver side duct when idling, this usually means that it is short of refrigerant. The refrigerant enters the evaporator on the passenger side duct and if there is not sufficient refrigerant in the system it does not circulate the entire evaporator before losing some of it's cold. If the difference in temps was happening at all engine speeds, that would usually be an actuator problem.
Hope this helps--Good Luck

Blown427conv

Great advice bestvette, I'll check the pressures as you suggested today. I did think about evacuating and reservicing it, I have the equipment available, just have to buy the freon and oil. Might just add some depending on what the gauges show though and see how that does. It was over 100 degrees yesterday when I added the can and the gauges were right at the top of the safe color at idle. Not sure what the pressure was though but will definately check it at 2000RPM today.

lucky131969

PM sent.

Bill Curlee

With a 75 PSI high side pressure, that tells me that the compressor is bypassing high side pressure. Theres a bypass valve built into the back of the compressor. With the low charge that valve may have been malfunctioning and when you added R-134, it may have allowed that by-pass valve to work properly again. NO WAY will adding 12 oz of fluid raise the high side pressure that much by it self. If it were that low, the low side would have been out of spec to. Measure the system pressures on BOTH the high and LOW side with the proper enviormental factors and HVAC parameters and see what you get.

BC

Blown427conv

I added more freon bringing both high and low side gauges to the top of the safe zone on the gauges and now I have cold air on the drivers side as well as the passengers side, even at idle. When I checked the pressure with the engine at 1500RPM both readings were low before I added more, so it definately makes a difference servicing the system at idle vs 1500RPM. I found that I have a small leak at the low side Schrader valve that I can't stop. The valve is tight in there and I tried popping it a couple of times to get it to seat with no luck. I put the cap on tight, but I will have to evac the system to replace it. At least I know the system is functional. Thanks to everyone for helping me figure this out.