Project C4, 85 Corvette

[Steve85]

TL;DR - AC works!



The full story:

I got the lines back Nostalgic and they looked great, perfectly aligned with my marks and ready to install. I started to second guess whether it had actually been converted to R134 since the fittings for the manifold gauges were not 134 sized fittings and there was a mix of black and green o-rings even though the hoses that were on the car when I bought it were clearly aftermarket and 134 compliant. I started poking around some more and found this blue orifice tube. Apparently, converted GM systems work better with the blue "Ford" orifice tube, there would be no other reason to have a blue one in this car.



Feeling better, I went ahead an oiled up the o-rings and installed all the hoses and the accumulator. Since I never removed the other components from the car (condensor, evaporator) and was careful not ever spill the oil out of the compressor or accumulator, I felt pretty confident I didn't need to add much oil. I added about an ounce to the suction side line (big one on top) for a little insurance though. I decided not to flush the system either since everything was removed in working order. 



get out your big boy wrenches



Looks pretty factory!



Installed the r134 fittings.



Installed and ready to be charged. I picked up some manifold gauges and an air operated vacuum pump from HF for less than the price of one hour of labor for someone else to do it. Of course if you get it wrong and nuke your compressor, gonna wish you paid someone.



The process is pretty well documented in various youtube videos. I watched a couple over and over so I could get the process down in my head. At a very high level, it's pretty straight forward, just need to make sure you're square on which valves to open and close and when. There were couple times during this process some refrigerant spit out (purging) so make sure you have gloves and eye protection!

Wall of text process I followed:

1. Connect hi (red) and low (blue) side fittings to car, open valves.
   
2. Connect vac pump to yellow gauge line
   
3. Open valves on manifold
   
4. Connect air line to vac pump to begin evacuation
   
5. Recommendation is 30 minutes, I did 15 since I didn't flush and my compressor was running constantly to run the vac pump.
   
6. Low side gauge should hit 28-29" of vacuum pretty easily indicating a leak free system.
   
7. Close hi and low valves at the manifold and turn off pump.
   
8. Monitor low side gauge for about 15-30 minutes, there should be almost no loss of vacuum, it definitely should not be dropping steadily.
   

If all good with holding vacuum, continue:

1. Leaving all valves as is, remove vac pump from yellow line and connect to a freon can. (You'll need a valve that goes on the can that pierces the top and has a connector to the yellow line)
   
2. With the can pierced and the valve on the can open, slowly loosen the yellow line at the manifold to purge the line of any air. 
   
3. Start car and set to max AC. (I think this typically engages the cooling fan and/or condensor fan to maximize air through the condensor and keeps the system working it's hardest. If you have a mechanical fan or the max AC feature is not wired up yet, use some other fan pointed at the grill, I used my "Blue Blower". It was interesting that the vent temps where 5 degrees cooler at idle when the my blower was running so it definitely has an impact!)
   
4. SLOWLY open the blue valve at the manifold, freon will begin to flow into the system. (My compressor started cycling on but for very short stints, as more freon got in the system, it stayed engaged longer and longer. The pressure on the low side will cycle at like 45 to 55, and as freon is added the range drops)
   
5. It may be necessary to slowly turn the can horizontal on occasion to get the freon to flow into the system. Not a good idea to turn it upside down quickly and flood the system though. Help it, don't force it.
   

To switch cans - 

1. Close blue valve at manifold
   
2. Slowly disconnect yellow line from can valve (I covered with a rag to prevent any residual spray)
   
3. Put the can valve on a new can
   
4. Connect to the yellow line
   
5. Open the can valve
   
6. Purge the yellow line at the manifold again
   
7. To resume charging the system, slowly open the blue valve at the manifold.
   
8. Repeat until you have added the proper amount of freon (for a conversion, you use 80% of the recommended R12. My car calls for 44oz of R12, I put 34oz of r143. It should take 35.2, but I went with 2 11oz cans and a 12 oz can for a close enough. I already had 3 11oz cans, which is why I didn't do 2x12 +11)
   
9. Monitor vent temps and low side pressures. (novice advice here, my high side gauge stayed at 0, not sure why but the system was operating so it had to be something with my valve positions. I was so worried about "DON'T OPEN THE HIGH SIDE" that I didn't mess with it. Also, all those recharge kits in the store ignore the high side.)
   
10. Vent temps should down in the low 40s
    
11. Low side pressure should cycle 30ish to 45ish (Exact pressures depend on a lot of factors but almost every video I've seen and my own experience, is in this range)
    

To stop charging - 

1. Close the valve on the freon can
   
2. Close the valves at the fittings attached to the car
   
3. Close the manifold valves
   
4. Disconnect the valves from the car
   
5. Remove the can from the yellow line (might be some leakage here, use caution)
   
6. Open all the valves on the gauges to purge everything (I really didn't get much, if anything, coming out)
   

That was about it! 

Some tidbits I learned along the way:

• r134 hates being overcharged, too much in the system will reduce performance
  
• A blue orifice valve is a good idea for a GM system converted from r12 to r134, especially if performance is poor at idle/slow speeds.
  
• It's just a process like anything else, not sure why I waited so long.
  
• If rewiring the compressor, it definitely needs a solid ground.
  
• The amount of air being pulled across the condenser has a big impact on system performance. If you've installed a smaller fan, an underdrive pulley (mechanical fan) or anything that would reduce this airflow, it will impact the temps you get from the vents.
  
• This old compressor takes a PAG 150 oil for use in a r134 system. I did see some caution around using PAG in a conversion that it can react with left over chlorine in an old r12 system. Mys system was open so long and previously converted so I went with PAG 150 with UV dye. If you're doing a conversion ona GM car, safest bet is a GM oil designed specifically for this. It's discontinued but still available through Amazon.
  
• If the compressor exploded and spewed it's guts through the system, then flushing is a must! If you don't know why the AC was removed, probably a good idea to flush and see if you get metal particulate. If so, you need a new accumulator and orifice tube at a minimum. Try to flush the heck out of the evaporator and condenser because the freon will just pull it all back to the compressor and explode the new one. A new condenser if fairly cheap, might be advisable insurance.
  

Pics
Gauges showing a good seal after 30 minutes


blower set up



Vent temp progress as I was adding freon







YEEEEESSSS!



sweatin it out



Low side pressure cycling




To do yet:
Compressor is juuuust hitting hood support, so need to cut some of that away
Clean up compressor wiring
Wire max AC setting to cooling fan

Very happy with what I learned along the way, how it turned out so far and looking forward to driving it whenever.

If anyone needs ACsistance or some gauges to borrow, let me know!