I have a 1971 442 I recently purchased, when trying to turn on the AC, the compressor clutch will engage for a second and then stop. The heater and all other vent controls work but no cold air. I have a CSM but am not good with AC and trying to read the diagnostic section cant really tell where to start with a compressor cycling off quickly. The compressor seems to be the original Frigidaire R12 compressor. My question is in this situation what would be the first step in diagnosing the issue? Again not really good at AC systems any help would be appreciated. (attached below are some pictures of my compressor, evaporator, condenser ect.

 

Attach a set of gauges. That should be first. Establish you have Freon in the system, and how much.

 

Your car has been converted to a Clutch Cycling Orifice Tube system, which is what that aftermarket assembly with the switch and blue cap is next to the evaporator box. The massive A6 compressor wasn't originally designed for cycling operation, though GM did use it as such in the late 1970s before replacing it with the R4 compressor. In any case, that pressure switch will disable the clutch if the pressure in the system is too low. I suspect this is your problem. The freon needs to be topped off.

 

X2, probably low on refrigerant. Are there any labels to indicate a conversion from R12 to 134a? The blue cap on the low pressure port may indicate a conversion has been done. It is very important to know before charging and not to mix the gases.

 

I guarantee that it was converted to R134 when that CCOT conversion kit was installed. The low pressure fitting will be a 134 fitting.

 

Is the 134a fitting different from the R12? Is there any other way to be sure if it has been converted? Unfortunately I cant contact the previous owner to see if it has been converted

 

Yes, which is why I said that above.

 

Utilizing the above logic, I can *assume* that the AC on my 71 442 has not been converted and is old style R12. Thank you

 

The adapter under the black cap indicates it was converted.

 

Thought so, but was thrown off by the lack of a blue cap.

 

^^^This! Yours doesn't have the CCOT conversion, but it is still running R134.

 

As always, thank you SB and JP, been under your tutelage for quite some time, and very appreciative

 

Is that fitting what is also called a shrader valve? I've done battle with the A/C on my '69 for almost 9 years (wouldn't hold an R134 charge after getting the original compressor overhauled) until just recently when an A/C guy told me my original valve was leaking and needed to be changed. Changing it and also the high pressure valve just behind the compressor (red cover) has made the difference so far. Mine has the "CCOT conversion kit".

Randy C.
'68 4-4-2 convertible
'69 4-4-2 convertible

 

To The OP, your ac system needs to be hooked up to a set of ac gauges, I’ll bet the system is empty due to a leak, but maybe just low on R134, either way the low and high pressures will determine what you need to do next. Please don’t add refrigerant until you checkout the system.

 

Yes that is a Schrader valve.

 

The Schrader valve is inside the fitting. It's just a tire valve.

 

Im waiting on a set of gauges. Asuming my freon is low what psi range would indicate that and if adding 134 back through a manifold gauge how do you know how much to add? Most everything I read is how many ounces to add to an empty system but what if its not empty and just low? Thanks.

 

There are tons of utube videos you can watch, and many how to’s online…
The ac system is a closed system, so if the system is low you need to find the leak and repair, just adding refrigerant is a losing battle.
Question, did your ac work recently?

 

The car is new to me and sat for a long time. I tapped the the schrader valve real quick and there is pressure in the system. So I guess I should extract the system, pull vacuum see if it holds and go from there? How many ounces is recomended for thar compressor?

 

The piece in the center is the core, the core threads into the valve body. Although similar in concept to tire valves, there are specific valve body and valve cores made for AC, they shouldn't be interchanged.

 

Your ac system originally held 4# of R-12, the conversion to R-134 quantity is about 48oz..

 

Any feedback on this guys methodology. Ordering a good gauge set today. Thanks

 

You can borrow (FREE) a gauge set from Autozone. That's what I have done. I do have a separate evacuating pump but those are very inexpensive @ HF.

 

Thanks VC that’s good to know

 

I have never been a fan of R134 replacing R12; however, when you could buy a 12- or 14-ounce can of R134 for a dollar or two, I couldn't blame people for converting their systems to R134 from the original R12. Today, a can of R134 is about $10, and people are asking an insane amount of money for R12, so it is still a popular conversion. When I say that R12 was being phased out in favor of R134, I stocked up on R12 and still do a few R12 repairs when necessary for my good friends who want to keep their cars original, "as built". For vehicles with leaks of refrigerant, the only way to stop an older car from leaking R134 is to replace all the refrigerant hoses with a modern product that has "barrier" hose construction. My 1962, which I re-hosed about 4 years ago and serviced/rebuilt, will lose a few ounces over the winter and needs to be topped off every spring. I have used a sniffer to no avail, and I think the only way I'll ever find that leak is if I buy one of the high-tech detectors that can do a better job of sniffing than a drug dog. I use the sight glass method to determine when it has sufficient refrigerant, along with monitoring both the high and low pressures.
If you have a system that is empty, it's best to do a complete service of the unit and do it right the first time, rather than chasing problems during the hot summer months when you need the air conditioning the most. If you don't feel confident in refurbishing or resealing the various parts of your car's air conditioning unit, I highly recommend Classic Air in Tampa, Florida. ( https://www.classicautoair.com/about-us/ )

 

Thank you @Junkman verry informative. I think at this point im going to try and recharge the system and see where that gets me. If it doesn't last long than I will evacuate the system and start from there with trying to find the leak. Thanks again everyone verry helpful.

 

When you do charge the system, make sure you get a can of refrigerant that has the fluorescent dye in it. It will make the leak visible enough for Stevie wonder to find.

 

Have you checked out your system with gauges, if so, what were the static and running pressures? Charge with R134, don’t use a product with stop leak…

 

So I tried charging with just 134 today and it took one 11 ounce clans, the compressor started to cycle on and off staying on for about 3 seconds at a time. When i went to put in the second can it wouldnt take any of it. I bought a gauge set but i need a 90 adapter to connect to the high side with the fittings i have its too close to the inner fender. Not sure what the issue is but im gonna put the gauges to it and see what my high and low readings are.

 

Sounds like it is still low on refrigerant. Wear eye protection, charge with the can upright so it goes into the system as a gas through the low side. Turning the can upside down will introduce a liquid vs a gas and will likely damage the compressor.

 

I’ve never seen the high side on the outside like that, a tight angle fitting might work if there is enough room to attach the fitting, if not you will have to loosen the assembly and move towards the engine side. I may have the fitting, I’ll check next week.

 

These cars have a sight glass in the dryer. It can be seen thru a hole in the radiator support. If I remember correctly, your suppose to run the system while observing the sight glass. Slowly add refrigerant until you don’t see bubbles, then add a 1/2 pound more.

No clue if a 134A conversion would change any of that, or if a cycling switch would create bubbles from the compressor starting/stopping constantly.

 

Matt - Since the AC was converted from R12>R134 (CCOT) hopefully the original drier was replaced when the system was opened (converted). I don't think they produce an R134 drier w/ a sight glass?

 

There is not a R134 specifc drier, and the driers I have used all have sight glasses.

 

R134 is used at 80% of what is called for with R12. The sight glass should have no bubbles and only an occasional "thread" moving through it. The oil in the compressor should be drained, and the proper oil for the R134 refrigerant should be installed. Also, the correct thing to do is to disconnect all the hoses and flush them to remove any old R12 oil. Many shops don't follow all the procedures to correct conversions because they are labor-intensive, and most customers don't want to pay the extra cost. Whenever I service an empty system, I change all the old butyl "O" rings to modern green Viton "O" rings. For these reasons, it is worthwhile to keep the unit at R12 rather than convert it to R134.

 

I looked, but can’t find my 90* adapter. Here’s a pic of my setup with gauges attached. I charge my system without using the R134 fittings.

 

This is a good thread. I just replaced the diaphragm actuator (photo) and vacuum hoses (6) on my '65's HVAC control. They now work properly. System still has pressure, albeit low, and compressor engages. Keeping it R12; 2023, I paid $105 for seven cans. My plan of attack:

1. Measure system pressures.
2. Replace drier.
3. Replace expansion valve. Should I?
4. Evacuate system, confirm it holds ~28" Hg vacuum.
5. Recharge with 3.75-lbs R12.

Thoughts? Do I need to be concerned about oil level?

 

Replace the drier, if the system has been working recently, I wouldn’t replace the expansion valve.

 

System hasn't operated for at least 15 years. I already bought a new drier ($12) and expansion valve ($15).

 

I would replace the expansion valve.