Automotive Air Conditioning Information Forum (Archives)

Provided by www.ACkits.com

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

'82 Chev C20 R134 Conversion

mrdap on Wed May 13, 2009 2:55 AM User is offline

Year: 1982
Make: Chevrolet
Model: C20
Engine Size: 454
Refrigerant Type: R134
Ambient Temp: 100
Pressure Low: TBD
Pressure High: TBD
Country of Origin: United States

Hello to All,

I appreciate all the help I received on this forum for my '89 Blazer. Now I have some new questions for the group on my '89 C20.

Ambient conditions: I live in Tucson, AZ. Normal is 100% low humidity, can get up to 107 to 115 in summer.
Evaporator, condenser, aluminum tube all flushed and blown dry.
New compressor (A6)
New hose assy (AC Delco)
New accumulator (AC Delco)
New retrofit cycling switch (FJC #3225)
Ester oil
Using R134 (original was R12)
Factory GM Chevrolet service manual calls for 3 lbs 12 oz (or 60 oz of R12) (capacity on sticker on evap case is unreadable)

Questions:

1. How much R134 should I use?
I have read anywhere from (start at 70% of R12 and add one ounce at a time untill optimum performance is achieved", to "use 85%", to "use 90%"

2. How much oil do I use total?
The instructions in the factory GM Chevrolet service manual are confusing. However, both the manual and the sticker on the compressor call for 10 oz compressor capacity. Is that 10 oz for the compressor plus x oz of oil for each component per the manual (see pic)?

'82 C20 Factory Manual

Or 10 oz total capacity for the system?

3. Which orifice tube should I use for best performance in desert conditions?
I have the following (new) tubes on hand:
GM white 15-5151/3033879
Ford Blue FJC #3016 (I have read that this improves performanance in GM systems retrofitted to R134 because of the smaller orifice)
Extreme duty (105 deg+) Smart VOV (variable) AC Delco 15-50122/19189843

I thank you in advance for taking the time to read all of this and answer my questions.

Regards,

DAP

Edited: Wed May 13, 2009 at 2:56 AM by mrdap

iceman2555 on Wed May 13, 2009 9:55 AM User is offlineView users profile

First suggestion would be to recharge the system with R12. The system was designed for this refrigerant and will offer the best performance with R12.

Fortunately this vehicle is one of the 'easier' units to do. The grill size/condenser size offer a maximum of condenser cooling. The lack of condenser cooling is a major factor in poor retro fit performance.

A personal prerogative is to use a Double End-Capped PAG 150. The viscosity of this lube is much closer to the OE spec'd for this unit. Years ago, we played with various orifices to determine what works best.....the standard GM unit performed as designed. The variables, although sold as magic cure, did not offer the same cooling performance. The use of a smaller orifice (blue Ford) did not produce a significant change in true evap temps. Adjusting cycling points of the LPCO was suggested as a method to enhance cooling. This procedure was later changed by the same people that proposed this adjustment.

The key to AC cooling performance is, of course, the amount of refrigerant within the system. Insure that the system is completely and properly recharged. A recharge rate of 90% should be acceptable in the vehicle. When making determinations, be sure to add for the amount of refrigerant necessary to pre-fill your manifold/ac hoses. Normally about 4 oz. It is assumed that you will be using 'cans' of 134a to recharge the system. This procedure does have it's draw backs, most noticeably knowing exactly how much refrigerant is being introduced into the system.

A good prevent test:
1.) Vehicle in sun (high heat load)
2.) Max Cool (recirculate mode)
3.) High Blower
4.) Doors open (high heat load on evap)
5.) Engine @ idle

Introduce refrigerant into the system until the the inlet of the evap (cool side of orifice tube) and the outlet (prior to the accumulator) are the same temp. Measure these temps and once the temps are equal or within 3-5 degrees of each other the system is properly recharged. The system must stabilize prior to conducting this test. Normal time for a system to stabilize is 5-7 minutes. If the outlet is warmer than the inlet, the system needs additional refrigerant. Adding an ounce or two at a time will work. Once more allow the system to stabilize. Recharging with a recharge machine will allow for a more constant recharge that the use of cans.

One the inlet and outlet are the same temps, the system is properly recharged. Evaluate pressures at this time. If an excessive high side pressure is evident, do not remove refrigerant to lower this pressure. Insure that the engine cooling system is performing as it was designed. Additional cooling fans maybe required to lower these excessive pressures. It is essential that the condenser be cooled properly. This enables complete transition of refrigerant gas to liquid and also has a serious effect on evaporator cooling.

One of the possible downsides of retro fitting an A6 compressor is the possibility of refrigerant leaks around the shaft seal. These compressors are constructed in the manner as they were in the 60's. Seals were not tolerance for 134a and shaft seal leaks may be an issue.

Good luck with your repair

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

TRB on Wed May 13, 2009 10:06 AM User is offlineView users profile

Quote
Originally posted by: iceman2555
One of the possible downsides of retro fitting an A6 compressor is the possibility of refrigerant leaks around the shaft seal. These compressors are constructed in the manner as they were in the 60's. Seals were not tolerance for 134a and shaft seal leaks may be an issue.

Good luck with your repair

We now have the option not to use the old A6 compressors.



-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

mrdap on Wed May 13, 2009 10:12 AM User is offline

Iceman,


Thank you for your reply, and all the detailed info.

A bit more additional info:

I fill from drums of R12 or R134 using a scale (not cans) but I don't have a charging machine.

So even a new Harrison A6 has old style seals which are not compatable with R134?

Also, still need some guidance on the oil capacity. Is the 10 oz of oil compressor capacity or total system capacity?

Thanks

DAP

mrdap on Wed May 13, 2009 10:14 AM User is offline

TRB,

Thanks for that.

Unfortunately, I already have the Harrison A6. Next project I will consider the Hodyon.

DAP

mrdap on Wed May 13, 2009 10:34 AM User is offline

Also,

Is the Double End-Capped PAG 150 compatable with R12 in case I want to go back to that in the future?

And is it compatible with Ester as, even though the system is flushed, it had Ester in it before?

Thanks

iceman2555 on Thu May 14, 2009 9:18 AM User is offlineView users profile

If a good flush was used,the POE's should be removed.
If the system were to be 're converted' back to R12. The lubricant should be flushed from the system and the correct type lube (mineral) reinstalled. This idea that there is a 'true' universal lube lacks validity. The best method to insure a proper operating system is to use the chemicals designed for the system.

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

mrdap on Thu May 14, 2009 9:22 AM User is offline

Thanks for the info so far.

Can anyone comment on system oil capacity?

Thanks

DAP

bohica2xo on Thu May 14, 2009 11:58 AM User is offline

Your system oil capacity should be around 10 ounces. Your manual should say something about finding more than 8 ounces in the compressor to be a possible oil overcharge.

Be sure you add most of the oil to the A6's sump - if it came with oil, you may want to flush it with whatever oil you plan to use in the system.

Now, back in the day the standard "oil level check" was to crack the drain plug on a charged system (this was even in some Frigidaire manuals). If only gas escaped, it was "low on oil".

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

mrdap on Thu May 14, 2009 1:07 PM User is offline

Thanks for that, Bohica

Interesting tip

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.