All the O-rings
must be changed as well, lube the o-rings with new oil, I am currently fixing my system

 

since this post has been resurrected ,
does anyone know if there is any information about all the O-rings and gaskets for the entire ac system for a 1990 b350 5.9? haven't been able to find any info.

 

You can get O ring kits with all sorts of sizes. They are usually a green color instead of the black ones on older years. There may be gaskets in there somewhere but I can't think of anythong other than the O rings at the line connections. I think back in the 1960's there may be some but usually just the ring gaskets.

 

I have the O-rings kit that also brings gaskets for what they call the block fittings , but my issue is that the system was played with before so I don't trust what's there.

 

I can see your point, I think there should be stickey on 134 conversions. This is for all R12 vehicles not just one model. I'm sure these questions were brought up else where on this forum. I know I see them in the first gen ram section. I did a search and didn't find anything. If anybody gets bored have a look in the tech archives. A lot it is worthless because the pic's are not available links no good etc. But some interesting stuff there. I was going to bring this up in the site issues and suggestions section but never did. But R12 to 134A conversion info is readily available via Google search:
Converting a vehicle's R12 A/C system to R134a involves replacing the service ports with R134a-compatible quick-connects, flushing the system to remove R12 mineral oil, replacing the receiver/dryer, adding the correct R134a-compatible PAG oil, and recharging with the appropriate R134a quantity. Simply adding R134a to an R12 system will not work because R134a requires different oil, operates at higher pressures, and can leak through older rubber hoses and seals designed for R12.

Why a Conversion is Necessary

• Oil incompatibility:
  R12 systems use mineral oil, which is not compatible with R134a and will cause the new refrigerant to fail.

• Pressure differences:
  R134a operates at higher pressures than R12, requiring modifications to the system's components to handle these pressures.

• Material compatibility:
  R12 has larger molecules than R134a, so older rubber hoses and seals will leak R134a.

• Fitting differences:
  R12 uses threaded service ports, while R134a requires quick-disconnect fittings.

Steps for Conversion

• 1. Recover R12:
  Safely recover the existing R12 refrigerant using a licensed professional with proper equipment.

• 2. Replace Service Ports:
  Install R134a quick-connect fittings on the high and low-side ports to accept R134a gauges and hoses.

• 3. Flush the System:
  Flush the entire system with a suitable flush solvent to remove all traces of R12 and its mineral oil.

• 4. Replace the Receiver/Dryer:
  The receiver/dryer should always be replaced during a conversion.

• 5. Convert or Replace Major Components:

• Compressor: A larger displacement compressor is needed for R134a systems, so replacement may be required.

• Condenser: R134a systems require a larger or more efficient condenser to dissipate the higher heat load compared to R12 systems.

•  

• 6. Install Barrier Hoses:
  Replace all rubber hoses with new "barrier" hoses that are specifically designed to prevent R134a leaks.

• 7. Vacuum the System:
  After all modifications, evacuate the system using a vacuum pump to remove all moisture and air.

• 8. Add R134a Oil:
  Add the appropriate type and amount of synthetic PAG oil for R134a systems.

• 9. Charge with R134a:
  Use a scale and a conversion chart to add the correct weight of R134a refrigerant. A common guideline is to use about 75% to 85% of the original R12 charge weight.