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?

[shortboxin]

Originally Posted by twinturboc10

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

Never even thought that was something I should do. Would probably need a thermocouple for that, right?

[kglowacky]

a long shot. make sure your heater box is working properly, maybe your diverter that flips the blower air to the heater core tunnel is sending your ice cold air through the heater core. Instant heat rise. just a long shot thought

[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?

[shortboxin]

Originally Posted by kglowacky

a long shot. make sure your heater box is working properly, maybe your diverter that flips the blower air to the heater core tunnel is sending your ice cold air through the heater core. Instant heat rise. just a long shot thought

When I switch from HOT to COLD on my controls, the temp changes drastically. It may not be anywhere near a perfect seal, but it's getting the majority of the air through the evaporator.

[shortboxin]

Originally Posted by 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?

My concern wasn't the fact that I didn't fill the system with 44oz, it's that the low side is running 90PSI and the high side is 330PSI. I'm afraid it's going to blow hoses, evaporator, or condenser.

Compressor "S" connected to the accumulator and the "D" to the condenser.

[shortboxin]

Going to throw this out there...

On another site a week ago, I was asked what orifice tube I was using. Just this morning while pondering this, I wondered if this could be the root of the problem. While I'm using the original style white orifice tube, maybe the Sanden small displacement compressor can't keep up?

Let's say initial balanced pressure is 225PSI and I switch the AC on. Compressor drops low side a bit and increases high side. As I stated, the low side never drops below 90PSI, so the compressor never turns off. Is it possible that the orifice tube opening is too large and allows too much flow for the compressor?

Please chime in. Thank you.

[twinturboc10]

On the oil thing - it looks like most Sanden compressors ship with some amount of oil, which is supposedly listed on a sticker. Something to check.

The high pressures point to insufficient heat rejection through the condenser and evaporator or overcharge. That’s why I was curious about line temps. If the condenser can’t get the refrigerant to a liquid it won’t cool. System temps increase and that drives up the pressure.

The displacement of the new compressor is about half that of the old R4, so it will move less refrigerant and heat. A smaller orifice might help. You could try dropping from the OE white 0.072” orifice to a red 0.062” orifice. Dropping from 0.072” to to a blue 0.067” orifice is pretty common with r134a conversions using the OE compressors.

[shortboxin]

Originally Posted by twinturboc10

On the oil thing - it looks like most Sanden compressors ship with some amount of oil, which is supposedly listed on a sticker. Something to check.

This is a knock off Sanden and it does not have a fill hole on it anywhere.

Originally Posted by twinturboc10

The displacement of the new compressor is about half that of the old R4, so it will move less refrigerant and heat. A smaller orifice might help. You could try dropping from the OE white 0.072” orifice to a red 0.062” orifice. Dropping from 0.072” to to a blue 0.067” orifice is pretty common with r134a conversions using the OE compressors.

Bought both yesterday, will start with the red. Also got a gallon of flush that I will run through the evap and condenser before evac and charge. Thanks.

[shortboxin]

1. Flushed out the evaporator and hoses. Removed the condenser and flushed out.
2. Changed the orifice tube to the .062" RED.
3. Replaced the accumulator and added 6.5oz of PAG 46.
4. Evacuated the system for about 5 hours.
5. Charged the system with almost 3 full 12oz. cans of R134.

Pressures came down considerably this time and it cools a little better than before, even with an outdoor temp of 103° instead of 98°. Vent temp getting down to around 75° at idle.

LOW = 63PSI (90PSI previously)
HIGH = 275PSI (330PSI previously)

Took it for a drive and the vent temp dropped as low as 52° on the freeway, so that's an improvement of 6° even on a warmer day.

Additionally, the accumulator and suction hose was hot last time and this time it's nice and cold.

FINAL THOUGHTS: 1. I will investigate to make sure my blend is porting all of the air across the evaporator. 2. I may also add a ball valve to the incoming heater hose line so I can close it off during summer. I believe this is as good as it will get without changing out the condenser to parallel flow.

Thank you for all of your help!!!

[whitelightning603]

Your persistence paid off. Sometimes you just have to keep digging. Recently I replaced the compressor on a family members 2000 Jeep Grand Cherokee. Also replaced receiver-dryer and a high pressure tube that had a 'captured' orifice. Pulled vacuum and it held. Started to charge it. Took the 1st can- then wouldn't take any more. Put refrigerant in warm water, waited long time, wouldn't take any more. The low side hoses were hot and it would freeze in that tube that had the captured orifice. Asked the local a/c gurus, they said maybe blockage or orifice stopped up. This tube with the orifice is a replace only deal.So I removed it and opened it up with a tubing cutter. Orifice was clean as new (which it was). Now bear in mind I had some older gauges and had gotten adapters to fit the quick connect 134 fittings. Both low and high side gauges had readings. Finally I removed the receiver dryer (which had the fitting) and the high side hose that had that fitting. What I discovered was that the adapter for the low side fitting was only opening the schrader valve enough to let the gauge read the pressure - but not enough to allow the refrigerant pass through. It allowed the 1st can through but connecting the 2nd can moved it just enough to stop the flow. So like you, I got to install everything a 2nd time along with another tube with orifice in it. Then used a different adapter and it charged normally. I didn't like doing all that work, but have to admit it gives you pride to say "it didn't whip me". Good job sticking with it.

[shortboxin]

Originally Posted by whitelightning603

What I discovered was that the adapter for the low side fitting was only opening the schrader valve enough to let the gauge read the pressure - but not enough to allow the refrigerant pass through. It allowed the 1st can through but connecting the 2nd can moved it just enough to stop the flow.

Had a similar issue on my prior fill. I was opening up the valve all of the way and it wouldn't flow. I found as I closed the valve back down, the flow started into the system. It then hit me that the new cans have a spring loaded piston in them and if you open the valve all the way, it closes the piston. To combat this, I bought a side can tap. Works really well. Fills like nobody's business!

[twinturboc10]

Pressures look better. Low side could be a little lower. Are you checking at idle speed or higher? Check out this charging method:
http://67-72chevytrucks.com/vboard/s...95&postcount=7

[shortboxin]

Originally Posted by twinturboc10

Pressures look better. Low side could be a little lower. Are you checking at idle speed or higher?

Actually, I'm having an issue with idle speed as well. I'm lucky to get RPMs in the high 500s. This would affect pressures as well, right?

[jjzepplin]

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