What am I doing wrong-AC problems
 

I have removed and replaced all hoses and I added a underbelly condensor and quarter panel condensor with fan and retained the front OEM condensor and fan.Also replaced the receiver/drier and expansion valve.I filled 3 cans of HC12A about 3 weeks ago and it cooled great.I lost the charge do to a leak at the hoses leading to the expansion valve so I fixed that useing copper sealing washers,pulled a vacuum for 2 hours and left it overnight to make sure no leaks and there weren't any so I added 2 cans of refrigerant and nothing,my low side pressures are 70 to 80 and my high side are about 60,do I have a bad expansion valve?I am really pissed right now as I have been working on this since Christmas and it's starting to warm up here,please any ideas are wanted.The car is a 83SC with a Sanden compressor.Thanks

Now I feel like I am in a Twilight Zone episode.After writing my original post I called Charles Fox at Fox Tool and Supply where I purchased my HC12A from and he had a couple of ideas but also suggested just drive the car and the AC will start working so I hopped in the car,turned on the AC and started driving,within 2 minutes the cold air started pouring out of the vents!!! It appears to be working fine,very strange.

Did Fox tell you why it would start working?

What kind of temps are you getting?

I haven't tested the temps with a gauge but it sure feels good.As far as why Fox thought it might start working is apparently the HC12A is thinner/lighter than R12 or R134A,because of this he thought it might take a little while for the expansion valve to start working correctly.At this point I am just going to monitor the temps and hope I have this done so I can move on.

Was the compressor really running (clutch engaged not just the belt turning) when you read those pressures: 70 to 80 psi low side and 60 psi high side? What type of oil do you have in the compressor? Jim

Yes Jim the compressor was running.The oil I am useing is mineral oil for R12.I am going to drive the car to work tomorrow and when I get home will hook the gauges back up and see what kinds of pressures I get with it apparently working.I expect around 30 on the low side and 100 to 125 on the high.

do you have a high/low pressure cut-off switch in the system?

There is one in the drier but I haven't wired it in yet.

Remember, lower low side pressure equates to lower vent temp.

This assumes you're close to proper charge, but in general, I agree. This is why condenser square footage AND airflow across the condenser(s) is crucial.

fuerst, are you using an expansion valve for R12? Those pressures are whacked.

Yes a expansion valve for R12.

When head pressures are less than suction pressure, it may be a restriction in the expansion valve (piece of trash or debris in the valve) or any restriction from the expansion valve to the compressor (like a kinked piece of tubing).