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Compresser A6 to S6 upgrade

HammerWerfer on Fri March 26, 2010 11:44 PM User is offline

Year: 1984
Make: Chevy
Model: C-20
Engine Size: 6.2l
Refrigerant Type: R12 -> R134a
Country of Origin: United States

FOLKS – Project on my 1984 Chevy C-20 Pickup with 6.2l diesel. Current A-6 compressor was running very heavy last season – Heavy enough to drag down the diesel. Tore 3 clutch hubs off the compressor.

Time to upgrade.

I am going to convert to R-134a. I will replace the factory tube and fin condenser with the Delco 15-6960 Parallel Flow condenser. The compressor will be replaced with the CoolPro S6, using BVA 100 POE oil. New accumulator, of course.

Set of instructions I have for the condenser states to reduce the amount of refrigerant used by about 3/4 lb (RPO C60)

At this point, Do I follow the 80% of R12 rule, reducing the oil inserted by an ounce? And which O-Tube should I use: Factory white 70 or the Ford blue 67 ? Anything else I should consider?

Thanks for the help.


iceman2555 on Sat March 27, 2010 4:39 PM User is offlineView users profile

First and foremost, there is not such 'rule' as quoted.....the system takes as much as it takes. However, some of the items listed on your 'repair' list will probably lead to a very short lived compressor. New condensers often will include a statement of adding or reducing refrigerant. 3/4 lb, 12 oz is a serious undercharge issue.
This compressor is nothing is simply a denso 10pa body with attachments to use in place of an A6. Personally, I feel the A6 was a better compressor, esp for your truck.
However, that being said, the most direct avenue to a failed compressor is undercharging a system. This process decreases the amount of lubricant available for the compressor. The A6 did not have this has a 'sump' and maintains lubricant.
First, insure that the system is thoroughly clean...flush..flush...flush....and stay away from oil based or solvent (mineral spirits) based flush chemicals. Also, stay away from ZEP products...the chemicals can be very dangerous to use (highly flammable) and result in serious compressor failures if residuals are left in the system.
Blowing air thru a evap or condenser is not an indication of a merely indicates that air flow thru. This does not necessarily mean that refrigerant will also flow with the correct flow rate.
Flush and clean the system.
Add your lube....3 oz to the suction side of the compressor. Add the remainder to the inlet side of the accumulator.
Evacuate the this for about 30-45 minutes.
Recharging for this system may present a challenge. Several parts that account for the correct charge amount have been changed. Although the compressors are approximately the same internal sizes. The condenser is the questionable part.
Enough refrigerant will have to be added until the evaporator 'floods' matter what that amount is...and no matter what pressures are encountered. Try this, MAX COOL, HIGH BLOWER, DOORS OPEN, ENGINE @ IDLE. Introduce as much refrigerant into the system as possible prior to engaging the compressor. Using the compressor as a means to 'draw' refrigerant into the system is a very good method to cause internal compressor damage due to lack of lubricant flow.
If possible use warm water and can immersion as a means to pre charge the system. Warm water...not more than 100 degrees.
When using this that the low side charging valve ( manifold/gauge) is open. Then place the refrigerant can into the water. Placing the can in water that is too warm/hot and the valve closed may result in serious pressures within the refrigerant can and could result in possible can explosion.....this result is possible damage to surrounding human tissue.
Start the engine...allow the vehicle to reach normal operating temp...engage the compressor and add refrigerant until the inlet and outlet temps of the evap are the same or very close to the same temperature. Once this occurs the system is approaching the correct charge rate. Allow the vehicle to operate for app 7-10 minutes, this allows for the system to stabilize......then recheck the evap inlet and outlet temps. These temps should be equal...or within 3-5 degrees of each other. When this occurs, the system is correctly charged....if a high side pressure problem is encountered....address the cooling system performance not remove refrigerant to adjust operational pressures. Insure that the engine cooling fans/radiator or operating as designed.
There is no need to change orifice tubes....the GM unit will work well with the system...if the system is correctly serviced.

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