I have factory AC in my 64 (it was long ago converted to r134). I had it charged a few summers ago and it was working back then. Currently though when I pull the AC **** in the cockpit, I cannot feel the compressor clutch kick in. I have 2 questions for you experts:

1 - if the refrigeramnt has leaked out of the system, will this prevent the compressor from kicking on or would something else be causing this?

2 - I am pretty handy mechanically, but I have little working knowledge of AC systems. I do have the shop and assembly manual - is troubleshooting these systems something a novice could undertake, or is this a job best left for a pro?

How would you guys approach this?
Thanks
Tim

 

Unless something special has been done to your system, the compressor will run whether it has refrigerant in it or not. You do not want to run it with no/low refrigerant..........it will quickly heat up and can damage itself. A minute or two is not a problem, but running 10-15 minutes without a refrigerant charge is.

If you are low on refrigerant (or it all has leaked out) the compressor will not have a load, and you may not feel it kick in. Have a helper check this as you try to start and stop the compressor. It is easy to see if the clutch energizes. Alternately, you could also use a multimeter or a 12 volt bulb to see if the compressor clutch is getting power.

The Chevrolet Service manual (especially for 1965-66-67 years has EXCELLENT information. It will help you tremendously.

To quickly see if you have refrigerant in the system, use a small screwdriver or wooden matchstick and push on one of the Schraeder valves. If you hear gas escaping, you at least have some refrigerant. If all is silent, you have completely lost the charge. Next, get a set of refrigerant gages and manifold assembly and hook it up to the low and high pressure Schraeder connections. Blue to low pressure side and red to high pressure side. Then run the compressor for about 1 minute and report what you see.

We can help guide you through this.

Larry

 

Thanks Larry - that sounds like a good place to start - I will need to pick up a set of gauges, so it may be a few days before I can report my findings.
Tim

 

If you have an AC car, you will need a set of gages to monitor performance and charge refrigerant. Get a good set, as they can (will) last most of your lifetime with proper care.

Determine the type of connections you have to make sure things will fit. Do you still have the old style R12 fittings (probably) or did the previous owner change them out to R134a type (like Federal law states ) ??

If you know someone in the HVAC business, perhaps he will let you borrow a set of gages, or will come over and assist.

Larry

 

I believe they are r134a type - at least that is what the previous service station that charged it years ago told me. Not only was he a reliable honest mechanic, but he owned a 65 with factory air that he restored himself - too bad he retired and moved away. I don't know anyone else personally that is local to me, so I'm motivated to learn about this and I'm ready to get myself a set of gauges - I have some NAPA dealers close to home as well as a harbor freight.
Before I go there - I am assuming I need a vacuum pump as well?
Tim

 

Tim:

You will probably need a vacuum pump sometime in the future, so yes, eventually buying one is a good idea.

But you may not need it for your car this time.....depends on whether you have some refrigerant or have no refrigerant left in the system. I would probably wait until you verify the condition of your refrigernant charge.

A good place for both buying equipment and getting good advice is the air conditioning forum at www.autoacforum.com I highly recommend you visit this site. There is an active forum, a section on frequently asked questions, etc., and a section to purchase equipment including a Section 609 AC license for buying refrigerants (which you don't need if you stay with 134a)

Larry

 

Larry - or any others who can chime in - good news of sorts - I must have just had a loose wire as the compressor clutch is now working - I removed the connector to test it and I get 12.2 volts when the AC **** is pulled out and no volts when pushed in - when I reconnected the connector, the AC clutch engages each and every time. I confirmed I have r134a connectors - they look like a quick disconnect = with no external threads. When I push in on the red connector, I could hear a faint hiss - so I assume that means there is some pressure. When I push in on the blue I heard nothing. This was done with the engine off. With the engine running, I could not hear any hissing - could have been drowned out by the engine noise though.
Next Step? Get some gauges hooked up and report back ?
Should I try charging the system?
Tim

 

Start with gauges, tell us what the Low/High pressures are with the engine running and the A/C on.

1. Close the valves on the gauges to prevent R134 loss
2. Connect the hose from the red gauge to the "high" connector - which is associated with the hose running to the front of the car
3. Connect the hose from the blue gauge to the "low" connector - which is associated with the hose running towards the firewall
4. Start the car
5. Turn on the A/C
6. Note the gauge readings
7. Report back

Info on recharging your system (with R12) is here http://forums.corvetteforum.com/c1-a...placement.html

I do know know the correct gauge readings for a fully charged R134 system.

 

Jeff and Larry - Ok - bought a set of gauges and hooked them up per your instructions (which matched the instructions that came with the gauges). The needles never moved - I reread the instructions and checked all my connections and repeated - still did not move -
see photo



what next? - does this mean my system is empty?
Tim

 

I'm going to defer to Larry for a more detailed response, but yes your system is effectively empty. The reason it is empty is the question. Larry can provide better guidance than I on your forward plan.

 

Jeff - my wife reminded me tonight that the system never worked after we had a Connecticut Corvette repair shop work on our car a few years ago. They did a multitude of work unrelated to the AC - new motor mounts, spark plugs, wires, water pump, etc. The car went into their shop originally for a broken valve spring and, well, one thing led to another. The work they did above was first rate - the car has run great since, but now I wonder if they disconnected something and did not tell me and drained the system. I read through some of yours and Merchons posts about various AC topics and it looks like I should as a minimum replace the dryer. Any other help would be appreciated. I'm going to reread my 64 shop manual supplement section on the AC again to better understand things while I wait for your replies.
Thanks
Tim

 

What needs to be changed on a 1964 factory air condition to use the new refrigeramnt?

 

First thing you need to do is take the wires off the high-low switch and put a jumper wire in it`s place to by pass the switch. This should get the compressor to come on.When the compressor comes on you can see if it is cooling.If it cools, you need a new hi-low pressure switch.
If it doesn`t cool you are probably low on refrigarant. If the compressor does not come on with the switch jumped, See if you have 12 volts at the compressor.
Hope this helps.
Later
Tony

 

NOW you can go out and buy a vacuum pump.

Tim:

The first thing you need to do now is to find and repair the leak. It could be a compressor seal (likely), an o-ring, or a failure of some hose or metal component. I use a combination of a soap solution to find the bigger leaks, and a refrigerant leak detector for the smaller leaks.

The conversion to 134a could also have created some issues if not done correctly.......so we will need to consider that as well. What components (if any) were changed or likely changed during the conversion?? Hoses?? O-rings?? What refrigerant oil was used?? I think you get the picture.

I would first get a couple cans of R134a and using your new gage manifold, add some 134a to the system until the pressure is about 50 psig or a bit higher. You can add through BOTH the red and blue lines at this point.....it doesn't matter. Don't worry about air in the system. After doing this, use the soap solution (or buy a commercial HVAC leak test solution) and check each and every connection for leaks. Listen for any large leaks....but check everything you can.

I use a TEK-MATE electronic leak detector as well, but I am sure you don't have one of these. Cost is about $150. Without one, you will not be able to find a small compressor seal leak or a leak in the evaporator. But we can try and get around that.

Go ahead and buy a GOOD vacuum pump and also a new receiver/drier. We will replace the receiver/drier AFTER we locate and fix the leak.

A year or two ago, I had an old/original o-ring start leaking......which depressured my system. An easy fix.....but my point is that o-rings can go bad, and o-rings for R12 and R134a are different. If yours were not changed to the green color (HNBR rubber) they could be the problem. If your hoses are newer, but not the barrier-type needed for 134a, the refrigerant could be slow leaking through the hose wall. R12 refrigerant oil will coat the old rubber hoses and prevent this, but if the hoses are new (and non-barrier type) and 134a is installed, this could be the problem. So soap check the hoses and hose walls as well.

Let's start with this, and then go on from there. If you can't find a leak, then we will pull a deep vacuum on the system (with your new vacuum pump) and see if the vacuum holds. This will determine next steps.

Larry

 

Are you sure about this? There is no low-pressure cutout to protect the compressor?

 

If we are discussing C2 Corvettes, the answer is YES I am certain.

If we are discussing more modern automotive AC compressors, then the answer is different. I am not certain when this change began....but can find out if needed.

Larry

 

No need to do that. It's amazing to me that even the early units had no low pressure protection for the compressor!

 

Around 1977-78, GM switched over to the CCOT type of system. CCOT stands for cycling compressor-orifice tube. The older STV/POA/VIR system was discontinued

To cycle the compressor, a low pressure switch was introduced into the circuit, which caused the compressor to cycle off at a low evaporator pressure of around 28 psig. The compressor would start back up (energize) when the pressure got up to around 35 psig or so. This cycling action protected the compressor and acted like the STV/POA valve to prevent evaporator core freeze-ups due to low evaporator pressure. This design is pretty much the standard today.

A few manufacturers may have (or did) add a specific low pressure cutout switch to the compressor to protect it. I don't have info on this without further study. But this was JUST TO PROTECT THE COMPRESSOR FROM DAMAGE. Some home units (compressors) have this feature.

Now in the early 1970's, GM and others did add a HIGH PRESSURE and/or HIGH TEMPERATURE switch to the compressor to shutdown the compressor and prevent the compressor safety valve from blowing, and help protect the compressor from damage. It was called a SUPERHEAT SWITCH.

Larry

 

Tony:

This switch is not on the C2 cars. They started using this type of design in the late 1970's. Maybe your not old enough to remember this.

Back in 1964-67, you had a **** with a cable attached. When you pulled the cable it activated a switch under the dash on the evaporator housing. This switch energized the compressor. It was either ON or OFF depending on where you positioned the cable.

Larry

 

Thanks Larry - sounds like a plan - I already picked up 2 - 12oz cans or r134a - would that be enough for this test?

Tim