I've had this C5 for only 2 months and am trying to get the A/C to blow cold. The low side of the system has good pressure, compressor runs all the time A/C is on, Rad fan runs with compressor, but zero cold air comes from the vents. I am thinking maybe the orifice valve/filter possibly clogged or stuck? I am missing the lower air dam which I know doesn't help, but with the fan running I would think it would cool off some. Any ideas before I have to empty and re-evacuate the system for a valve change? I know a dying compressor will clog the filter, but I think I've heard of the valve sticking closed before on GM cars? Any opinions or suggestions are greatly appreciated.

 

Two questions? Engine running at 1000 rpm. AC on Max fan, Max cool.

1) What is the low side pressure

2) What is the high side pressure

 

I too had poor cooling with seemingly good pressures and a full freon charge. Even cleaned the condenser with some special spray on stuff I got at the AC supply store. Invested $3 for a new reed valve and also a small bottle of GM refrigerent oil. Discharge the system FIRST. Take out the bolt on the line at the passanger fender and remove the expansion reed valve. Mine was REALLY STUCK in the tubing. Finally squirted oil (as it was bone dry) and used some long nose vise grips. The reed valve is plastic or mostly as I remember. I twisted and pulled and PRAYED that it didn't break off. If it breaks and you have to change the rear line you are in for a fun time.
I also added about 4 oz of refrigerant oil (make sure its for R134A not F12) as the system seemed DRY. Lubed the new reed valve with refrigerent oil, reused the O ring as I couldn't find a new one at GM parts wholesaler or otherwise, evacuated the system with an old sealed refrigerator compressor I've been using for years, waited a half hr to make sure vacuum wasn't going down showing a leak, then charged the system. The C5 uses about 1.75 pounds of freon so I used 2 14 oz cans and used a bucket of HOT WATER to get almost all of the freon out of the cans.
Now the system cools like its in Alaska.

Good luck.BIGHANK

 

This can be diagnosed with pressures. To have a full system and restricted flow will show with very high pressures on the high side of the compressor.

 

This simple test will tell us something. With the compressor running, the "Accumulator" should feel "Icey" cold. Does it?

 

Heres where I'm at. The fans don't come on with the AC, the switch lights up and controls work fine on the control panel. (dual zone electric) The compressor comes on and stays on. Low side pressure is good, no high side gauge to check it yet. The fans only run on the slow speed with the engine temp, not the A/C. I figure I'll evacuate and change the reed valve, but would like to get the fans working first. No lines seem to be getting cold under the hood either so thats why I thought the reed valve, or worse, the compressor. Going to try to get a set of gauges to check the high side today. Any ideas on the fan situation? This car is aging me quickly with its quirks.

 

Also I checked the relays with power and all 3 click (big relays) and change resistance. Fuses all good.

 

One more thing, no HVAC codes either.

 

There is a suction and a discharge line running to and from the compressor. One should be cold and comdensating, the other should be warm or hot.

Are you sure the clutch isn't slipping and/or disengaging when you aren't looking?
If the compressor is compressing/turning, it's probably working. if you remove the belt and try to turn it by hand with car off, what does it feel like? If it turns smoothly it's probably ok.

EDIT:

This is your problem. Try this: Run cool water over the condenser. See if that helps the temp inside.

(By fans you mean external fans right? Not inside blower -- that's all working ok?)

 

I'll check again, but I am pretty sure both lines off the compressor are hot. I'm leaning towards the reed valve on this issue. The cooling fans are not coming on with the compressor. They do come on with the engine temp, but on low speed only. I had the car up to 228 degrees and fans ran in slow mode. With AC on, no difference in fan speed. The compressor stays on and does not cycle. Stumped on the fans. I checked the relays with voltage and can hear them click, and all fuses underhood are good. No HVAC codes on DIC either. I thought about the water idea, but I don't think the coolant is circulating since it never cools down even on the open road with plenty of airflow over the condensor. I'm open to any ideas on the fans, thanks in advance.

 

And the high side pressure is?

Reed valves? Are you referring to the ones in the compressor or do you mean the orifice tube. Most a/c have either orifice tube or expansion valve to control the rate of evaporation of the freon.

The only reed valves I know of might be in the compressor depending on design.

 

I was thinking of the filter looking valve in line, someone suggested is at the pass fender junction. They are usually about 4" long I think. This is the one I have seen clogged before on other vehicles, glad to know there are more valves in the system to make this more fun. The inline one is usually pretty cheap and available at under $10 I think. I am most concerned, at the moment, about the lack of fan engagement with the compressor engaged. Need to make it accross town to buy a set of gauges, probably tomorrow. Local parts house tried to gouge me on a set. Any ideas on the fans?

 

 

Check those fuses!!!!

BC

 

Also Harbor Freight was selling decent guages for $39. I bought a set instead of retrofitting my old R12 guages with hi and lo side adapters.BIGHANK

 

I got the fans working by moving relays around and jumping 12 volts to the cool fan 1 relay 1 time. (works now without jumper) Does anyone know exactly where the reed filter/valve is in the cooling lines? There is a union just forward of the firewall on both high and low press, but no other unions, so I'm guessing it is there. Is it on the high (small) pressure line? Neither line is getting cold and the compressor, and rest of the HVAC seem to be working fine. The clutch stays engaged when on and feels good by hand when I rotate it and try to wobble it when off. I never did get a chance to check the high side press, but the low side is good, so unless the compressor is bad inside, it has to be the $3 filter valve thing. Thanks for all of the usefull information on this.

 

Ok, it has to be the Orifice tube or the compressor, anyone know where to find the orifice tube? Is it at the small line at the firewall union? Thanks...

 

Hi, The Orifice Tube, which acts as the expansion valve on this system is located in the evaporator tube where the rear and front tubes are joined by bolts. Also the vette system is a Non Cycling Design, The comp should be running whenever the AC is on. Instructions Below.
++++++++++++++++++++++++++++++++++


Expansion (Orifice) Tube Replacement
Tools Required
J 26549-E Orifice Tube Remover
J 39400-A Halogen Leak Detector
Removal Procedure




Recover the refrigerant from the A/C system. Refer to Refrigerant Recovery and Recharging .
Remove the front evaporator tube to rear evaporator tube retaining bolt.

Important
Cap or tape the open rear evaporator tube immediately to prevent contamination.


Disconnect the front evaporator tube from the rear evaporator tube, discard the O-ring.




Important
Cap or tape the open front evaporator tube immediately.


Using J 26549-E remove the orifice tube.



Inspect the expansion (orifice) tube for the following conditions and clean or replace with a new tube as indicated:
Broken plastic frame; replace the tube
Filter screen (1, 2) torn, damaged or plugged with fine gritty material; replace the tube
Brass orifice tube (3) damaged or plugged; replace the tube
Filter screen (1) coated with metal chips, flakes or slivers; coating may be removed with low pressure shop air and reused if cleaned satisfactorily If reusing the orifice tube, install a new O-ring (4)
Installation Procedure




Remove the cap or tape from the front evaporator tube.
Install the tube (short filter screen outlet side first) fully into the front evaporator tube.



Remove the cap or tape from the rear evaporator tube.
Install new O-rings to the exapansion tube. Refer to O-Ring Replacement



Install the front evaporator tube to the rear evaporator tube.

Notice
Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.


Install the front evaporator tube to rear evaporator tube retaining bolt. Tighten
Tighten the bolt to 25 N·m (18 lb ft).

Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .
Leak test the fittings of the component using J 39400-A .
++++++++++++++++++++++++++++++++++

The orifice tube is located inside the front evaporator tube, the front and rear evaporator tubes join together by a bolted flange, back near the firewall along side the engine. But you are going about trying to fix this problem the wrong way. I'm not criticising, just trying to be helpful. The condition of no cold air in the car does not have to be either the comp, or the orifice. There are other possibilities. Logical diagnosing will save you a lot of headaches. You should have a set of guages to diagnose the problem. Even if you evacuate, flush, and replace the tube, you need both high, and low side guages to properly pull a vacumn before recharging, as the proper way is to pull vacumn from both sides, and then to check both pressures during recharge to evaluate the success of the procedure.
Other posibilities that could cause the same symptoms you are having are, bad control head, bad actuators, or need for actuator recalibration, clogged condenser, bad compressor control valve, improper charge, improper refrigerant, air or moisture in system etc, just to name the most common culprits.
Post the high and low side pressures at 1000, and 2000, rpm's and the ambient temps, and we can help a lot more.
Good Luck

 

OK, you are right on the cooling issue. I was trying to do what I've experienced in the past, but the Corvette is DEFINATELY like no other automobile I've ever worked on. Without this forumn I would still be trying to get the car to start, or still be trying to get a bad engine out of it. I'm praying it is something as simple as the orifice tube since I really really really don't want to take out anything inside the car. I am going to get the A/C gauges now with both high and lows. In the past I've been using only a low side gauge and a vacuum pump with a home made manifold. I have with great success R&Ring the orifice tubes and when necessary, compressors, but the Vette is definately another animal. Thanks for the continued support and I'll post the pressures ASAP.

 

Correct I gave up asking for High side pressure. Without the high side pressure you can't tell if the orifice tube is plugged or the compressor failing.