Since I am totally incapable of actually writing anything down, I have to look this up every time I do a conversion. For those that care, the blue Ford .067" is the:
1989 Ford Crown Vic with 5.0L FI will get you there.
AC Kits 31-50002
Parts America/Kragens/Autozone 46031
Four Seasons (blasphemy!) 38621
I guess you use the blue in place of the GM white when retrofitting? What kind of pressures are you seeing with those smaller o-tubes?
The only retrofits I have done are on the big old GM systems, and I kept the white 0.072 orifice. Getting the evap pressure down to 19 psi was no problem at 1500 rpm, but with the old condenser was seeing 250psi high. At least on my '80 Chev, was only getting mid 20s psi at idle, so not as cold as it could be. It does cycle on the highway, not sure if a smaller orifice would help that or not.
Sounds as if the Chevy is a bit undercharged. One mistake when retro fitting is the use of R12 pressures to determine the complete charge with a retro fitted system. Dropping the charge to obtain a lower evap pressure is not a sound policy for successful completion of a retro recharge. Replacement of the GM orifice with a the smaller Ford unit may actually result in a more serious problem...the possible restriction of refrigerant flow into a possible undercharge evap may result in the loss of lubricant flow back to the accumulator/compressor.
When the retro fit is accomplished correctly and the system is totally recharged, the system should work well with the standard GM orifice. The use of a Ford orifice is often the choice of many...however, many years ago, we tested this approach on a test stand and failed to see significant pressure/temp differences. This goes with the adjustment of the cycling switch. This was initially thought to be the 'magic' for a proper retro...however, this issue was also dismissed and test indicated too little change to actually contribute to a major operational temp/pressure change.
All in all...the best method to insure a proper operational R12 system.....stay with R12. Or make the necessary change to enhance refrigerant cooling....change the condenser to a more efficient unit...and then in most cases the system could be completely recharged to 12 specs with 134a.
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.
Was 3 years ago, but IIRC I ended up charging it to the full R12 amount (3.75lbs) because it was cycling too much. I also adjusted the LP switch to 19 psi, which also helped reduce cycling. But still, on the highway with low blower it would cycle off after about 10 seconds, 5 seconds later back on. Does that seem normal? Cooled beautifully, but with the non-computer engine could certainly feel the A6 engage. Actually, seemed to stop doing that on longer trips when the interior really got fully cooled.
I do know that my poor idle cooling is because of the condenser and fan clutch. Condenser is large, but still the OE tube and fin. Replaced the clutch with an aftermarket, probably time to get that GM part.
Edited: Sun March 30, 2008 at 7:33 PM by mhamilton
On a basic CCOT without variable compressor, cycling is essential when you're running the fan on low and getting good performance from the system. Otherwise the evaporator will frost up.
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