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Old 01-07-2018, 12:29 AM   #1
redozc4
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Default A/C help!

Hi all. Have an a/c question about my 1986 Vette.
I have broken what I believe to be the high pressure switch on the a/c line and I need a replacement before I can attempt to resurrect the a/c.
Question is, I want to run R134 gas and I will need the correct switch. Where can I get the correct part and will I need to also replace the low pressure cut off also.
I am in Western Australia and I am Curious if there is a compatible part number in the GM parts stable locally.
When the a/c was working, the airflow from the dash vents was pitiful to say the least, the blower was working feverishly but it seemed to be coming from everywhere except where I wanted it to. It will probably be door seals somewhere but it would be great if someone could narrow down my search so I’m not just stabbing in the dark.
Thanks in advance guys.


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Old 01-07-2018, 10:20 PM   #2
pcolt94
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I would first make sure that the vents are operating proper and the air is coming out where it should. But very likely the evaporator due to age is clogged up restricting air flow.

If you really want to convert to 134, the oil has to be removed and new oil has to be installed for the 134. The evaporator holds oil so if it is plugged up, it should be replaced. That way air flow is increased and the old oil is gone. All the lines have to be cleaned and blown out. The accumulator also has to be replaced. The oil in the compressor has to be removed by turning it upside down. Oil has to be installed in the new evaporator and compressor along with new seals. The pressure switch has to be replaced for the 134 where the cycle point is 22.5 psi.

These are some of the basics and a big job but to do it right that what it takes. There are shortcuts others take however I cannot comment on them. But I would read up on the process. I'm sure others will add their suggestions also.
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Old 01-07-2018, 11:21 PM   #3
Joe C
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recommended reading. I used FJC to retrofit my 85, and seems to have worked out OK - they have a complete parts listing .pdf, on-line. I bought most of my small parts on ebay, including the LP cycling switch. complete retrofit, not cheap, but I was not a big fan of the Walmart, $39 conversion in a can method - although some have had success.



to retrofit, you will need to flush the system, and change to either PAG oil or ester. ester is compatible with R12 and R134a, and that's the route I went. you will also need a new accumulator/dryer. I replaced my compressor due to a bearing failure - this triggered the conversion. FWIW, I have center duct temps as low as 40°F during the florida summers. BTW, when the wife tells you to turn down the AC because she's too cold, you know you've done something right!

Last edited by Joe C; 01-08-2018 at 06:57 AM.
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Old 01-08-2018, 03:03 AM   #4
xrav22
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I agree I used ester oil and I noticed I was loosing pressure to the vents because around the new heater core/ firewall the area needs sealed. Also where the tubes go into the evaporator.
I used some weatherstrip sealant to seal them u can check them. I converted to 134 and just replaced the high pressure switch with a standard one. I used a retro 134 kit from Ecklers Corvette.

Last edited by xrav22; 01-08-2018 at 03:06 AM.
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Old 01-08-2018, 05:44 AM   #5
The Thomas J
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I guess this thread explains why my recently converted AC is not ice cold. I just replaced the Compressor, seals and and blower control module. The shop may have replaced the high-pressure switch too. I have to check. I roast in that car in the summer. It causes me not to drive it. Once the temperature get's past the low 80's it's just not enjoyable to be in.
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Old 01-08-2018, 09:58 AM   #6
Kevova
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GM uses PAG oil. The restrofit book is a good idea.
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Old 01-08-2018, 10:34 AM   #7
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Quote:
Originally Posted by The Thomas J View Post
I guess this thread explains why my recently converted AC is not ice cold. I just replaced the Compressor, seals and and blower control module. The shop may have replaced the high-pressure switch too. I have to check. I roast in that car in the summer. It causes me not to drive it. Once the temperature get's past the low 80's it's just not enjoyable to be in.
The 134 is not as efficient in a system designed for r12. Your shop may have also decided to run at lower pressures because of your old hoses too. When I have done my conversions I go ahead and charge to the same pressures as r12 - a conscious decision since I warrant my own work!

If you have a clear targa top, you might consider applying a sun screen. I did and it made a huge difference in the south Texas heat. I may have the rear hatch area done too.
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Old 01-08-2018, 11:42 AM   #8
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no flames, just another point of view. good reading --

https://griffiths.com/ac-system-help.../r134a-vs-r12/

from that site -

Quote:
Q:Is R134a less efficient than R12?


R134a is NOT less efficient than R12 – Actually R134a is more efficient.

Pound for pound R134a is a more efficient refrigerant than R12, however it runs at higher pressures in some aspects and therefore requires more effective condensing. Whether R134a performs as well as R12 in any given a/c system depends upon system components and the amount of R134a used.

Given two identical vehicles, each with the same weighted amount of refrigerant, the vehicle with the R134a has the “capability” to remove more heat (measured in btu’s) from the vehicle than the same type of vehicle using the same amount of R12.

The most common influences which effect the capability of R134a to perform well are the condenser, in some cases the the superheat setting of the expansion valve or the amount of R134a. Condensers designed to release greater amounts of heat help to expel the greater amount of heat which R134a removes from the car’s interior. And by “matching” the correct amount of R134a to use in a given vehicle, correcting the superheat of the expansion valve (if necessary), you can in some manner nearly balance or match the amount of heat drawn out by the evaporator and released by the condenser.

These efforts to “balance” the system can not be realized if there are problems within the a/c system, such as: poor performing compressor, dirty condenser or poor air flow through the condenser, malfunctioning expansion valve, water or air in the system, improperly operating fresh air or heat input in the climate-air mixing system.
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Old 01-08-2018, 12:02 PM   #9
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Appreciate that Joe C!

I can see now how I would interpret the "less efficient" than r12 comment. The higher pressures needed for r134 would make charging an original r12 system "less efficient" if I were concerned about the whole system handling the higher pressure.

On the two older cars I have done the swap, I cleaned out the system and replaced the major parts as instructed, but couldn't bring myself to charge the system per r134 specs. In the end, I guess the systems were good enough as I really didn't feel much difference. Discharge temps were a bit lower, but in Houston's heat, they worked well for me. And one car was black.
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Old 01-08-2018, 02:16 PM   #10
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Quote:
Originally Posted by The Thomas J View Post
I guess this thread explains why my recently converted AC is not ice cold. I just replaced the Compressor, seals and and blower control module. The shop may have replaced the high-pressure switch too. I have to check. I roast in that car in the summer. It causes me not to drive it. Once the temperature get's past the low 80's it's just not enjoyable to be in.
I would first check the pressures with a set of gauges and see where the pressures and cycling points are. Also how long it takes to cycle on (close) after the cycling switch has opened.

If a wrong orifice tube was used if could affect the pressures as well as the cooling efficiency of the system. If it was not replaced it could be clogged. A clogged accumulator if clogged could also be problem. And from what I understand, if too much oil was used it might not cool efficiently.

Find out all they say was replaced, it should work better that stated.

Last edited by pcolt94; 01-08-2018 at 02:17 PM.
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Old 01-09-2018, 06:53 AM   #11
redozc4
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Well thank you all for the replies, I sure appreciate your time and knowledge.
what is clear is that I will get an A/C technician to have a look and tell me what works and what doesn't work and I will start to compile a parts list from there, I'm pretty sure that by the way the compressor has leaked oil over the years it will be better to get a new one rather than have this rebuilt, I will obviously need both high and low pressure cycle switches as well as a new receiver/dryer.
we'll see where we go from there.
Once again guys, thank you all.
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Old 01-09-2018, 06:57 AM   #12
redozc4
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Default with this West Australian sun and a bald head I have A/C envy!

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Quote:
Originally Posted by Joe C View Post
recommended reading. I used FJC to retrofit my 85, and seems to have worked out OK - they have a complete parts listing .pdf, on-line. I bought most of my small parts on ebay, including the LP cycling switch. complete retrofit, not cheap, but I was not a big fan of the Walmart, $39 conversion in a can method - although some have had success.



to retrofit, you will need to flush the system, and change to either PAG oil or ester. ester is compatible with R12 and R134a, and that's the route I went. you will also need a new accumulator/dryer. I replaced my compressor due to a bearing failure - this triggered the conversion. FWIW, I have center duct temps as low as 40°F during the florida summers. BTW, when the wife tells you to turn down the AC because she's too cold, you know you've done something right!
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Old 01-13-2018, 04:24 PM   #13
ctmccloskey
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I am not an expert on air conditioning but I have upgraded a few of them and filled many.

After purchasing a two-stage vacuum pump (Harbor Freight $75) and following A/C upgrade instructions everything worked in my favor. One important lesson I learned was not use the "Venturi" vacuum pump, it took a lot of air compressor time to get the vacuum you need.

After cleaning the lines and replacing all the seals I could and installing the evaporator on my 1988 C4 I pumped it down to 28 inches I let it sit for a several days and it did not budge. So next I filled it with the proper amount of oil and charged it with R134 and it has worked ever since. It is as cold or colder than the original system was when I bought the car.

One trick I learned many years ago was to clean the condenser once in a while. On Home air conditioning systems the condenser is one of the first things they clean when doing "routine" maintenance. Why wouldn't they clean car condensers like that?

The material they use is called "Coil Cleaner" and is usually a mild acid (phosphoric?) that dissolves the corrosion on the aluminum. This allows the heat to be removed more efficiently. I have found that some car wheel cleaners can cut through the corrosion quickly but keep it away from your cars Paint. On my C4 it is easy to clean the condenser without damaging the paint. Just rinse it down with lots of water when finished.

Getting the heat out of the condenser is a very important stage in air conditioning. Keeping the radiator and condenser clean makes the whole car work better.

Good Luck with getting your A/C system working again!

P.S. I also clean the fins of my radiator very few years the same way.
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