A/C issues on 84 C10 with 5.3 LS

[shortboxin]

I know, I know. A lot of info, but without it you won't know what I'm dealing with. Posted this on another site and it was suggested that I might have too much oil in the system. That appears to not be the case...

Evacuated and charged the A/C system on my 84 C10 and I'm having issues that I've never experienced before on any vehicle. Of course, it's a kluge, so I should've expected to run into some problems. It cools, but no colder than 78° at idle and it's got very high pressures. System was previously converted to R134 with the 305 engine and worked fine until I opened it up last August to swap in my 5.3 LS engine.

Setup:
Aftermarket fans with shroud which turn on when A/C is switched on (not the compressor cycling)
OEM evaporator
OEM condenser
NEW accumulator
NEW Sanden SD7B10 compressor
NEW custom suction and discharge hoses
NEW orifice tube

Blew as much oil as I could out of the evap and condenser since I don't know what was in it. Connected the hoses, but not until I added 6oz of PAG 46 into the system in various locations. Evacuated the system using a vacuum pump from Autozone. Pulled down to 28" of vacuum and left it for an hour.

Started adding R134 with an outdoor temp of 94° and a jumper on my low side switch until I got 12oz into the system. Pressures at that time with clutch engaged:

LOW = 28PSI
HIGH = 160PSI

Added my second can of R134. Low side jumper removed, but clutch was engaged 100% of the time as the pressure was too high for it to ever cycle off. Pressures now at:

LOW = 60PSI
HIGH = 230PSI

Added most of my third can of R134, but quit due to the high pressures. Probably added 8oz or so. This means I only have 32oz of R134 in the system at most. From what I can tell, capacity is 44oz with R12, so it's technically still 20%-25% low... Clutch still engaged 100% of the time. Pressures now at:

LOW = 90PSI
HIGH = 330PSI

Outside temp had climbed while charging and was around 98° by the time I finished. Interior vent temperature at idle is around 78° (give or take a few degrees), so not working too well. Drove the vehicle on surface streets as well as the freeway. Vent temp dropped to around 58°, but still not great considering.

Someone suggested that I might have too much oil in the system, so I opened it up and collected all of the oil that I could. Got some drips on surfaces, floor etc. Removed the condenser, tipped it and blew it out, blew out the evap, dumped out the accumulator (stored it upside down for 2 hours and kept tipping it into the cup), and dumped the compressor while rotating it four separate times. Still only able to collect just under 3oz total.

In addition, the 7B10 compressor doesn't have a fill hole, so the 6oz I originally added was probably about right. Any help is greatly appreciated!

[whitelightning603]

I'll be the 1st to ask a dumb question. Are you sure the fans are operating in the proper direction? I once replaced a compressor, condensor, and receiver/dryer - all because of a bad fan relay. I learned that day that there has to be heat transfer to properly operate. Good luck.

[shortboxin]

Originally Posted by whitelightning603

Are you sure the fans are operating in the proper direction?

Thanks for chiming in!
Yes, I actually wondered whether there was enough airflow last week, so I put my hand behind the fans (engine side) to see how much air flow there was and found that my hand was being blown on, so it's definitely the right direction.

[Dave]

I hate to ask these questions but gotta start somewhere so here it goes

1. How long did you vacuum the system down and what was your reading when you finished vacuuming the system
2. Did you wait till the next day and check readings again, to see if the vacuum held
3. The other thing to consider is the OEM condenser and evaporator were designed to operate for pressures for R12.
134A operates at a different pressure level, meaning the OEM evaporator and condenser will not be as efficient converting 134A back to gas and then to a liquid.
Eliminating the possibilities one at a time is how you'll find the issue.
Lmk what you find

[shortboxin]

Originally Posted by Dave

1. How long did you vacuum the system down and what was your reading when you finished vacuuming the system

Only one hour. I've done it this way on all of my Mustangs and it's worked every time. I had 28 inches of vacuum.

Originally Posted by Dave

2. Did you wait till the next day and check readings again, to see if the vacuum held

I did not wait more than the hour. Again, never had to do that in the past on Mustangs, even when they have been opened up for a year or more and I've never replaced the accumulator on any Mustang.

Originally Posted by Dave

3. The other thing to consider is the OEM condenser and evaporator were designed to operate for pressures for R12. 134A operates at a different pressure level, meaning the OEM evaporator and condenser will not be as efficient converting 134A back to gas and then to a liquid.
Eliminating the possibilities one at a time is how you'll find the issue.

System was already running 134A prior to the LS swap, so it should work. The only significant difference is the compressor it ran prior was the R4.

I only know enough about AC to get by, so I'm basing everything I've done here on what's worked in the past on Fox Mustangs. This is my first dive into LS motors and Chevy AC.

[twinturboc10]

Any chance you measured or observed temps in/out of the evaporator or across the orifice while charging?

[Richard]

The 134a charge is typically around 80-85% of the r12 charge so you are not far off. Are suction and discharge hoses from new compressor routed correctly?

[jjzepplin]

It sounds like you are tracking down the issues quite well. Keep up the good work.