• I have just finished some AC work (again ) on my 73 350 convertible that I have owned, and worked on for 50 years.
• My AC clutch is intermittently slipping and grinding, causing my AC system to be unusable. It worked fine when I was filling the system, but when I got it filled, the slipping started ( Maybe hydraulic lock up ) I feel like the compressor is working too hard.
• This is a new A6 AC Delco gold compressor / clutch and a new VIR eliminator from Old Air.
• I filled the system with R134a substitute. ( ZeroR 6oz equals 16 oz of 134a Not sure what that is. ) Had to add a little Super Tech 134a sealer conditioner to bring the low side pressure up to 35psi at 1000rpm at 70degrees.
• The compressor came with oil in it and I added 1oz for the VIR eliminator,
• I'm not sure if I got a bad compressor, or I've done something wrong.
• I would REALLY appreciate any help, thoughts, advice, experience, on this because I'm getting very frustrated
• Thanks in advance for your help.

 

You make no mention of evacuation of the system and checking if it holds vacuum and what was the high side pressure at 70 degrees.
How much R134 did you add?

 

I did vacuum the system down, and it held. It also is holding pressure.
I added two 6oz cans of ZeroR which should equal 32 oz of 134a and a partial can of Super Tech to bring the low side pressure to 35psi. My understanding is this system requires 38oz of 134a.
I can't tell you the high side pressure as there is no fitting to connect one.
I miss R12

 

My understanding is your original compressor was marked 2.8 lbs. The formula to go to R134 is (2.8 x .9) - .25 =2.27 x 16=36.32 oz.
Your original compressor had a manifold on the back of it with the high side port. What happened to that manifold?
See this link with pictures.
73 Ac

 

I have that. That is the low side I use for filling and pressure checking.

 

You really need a set of gauges. I've seen a few over charged in my day. One was reading 500 psi on the high side. But the belt was slipping not the belt. But anything is possible. Things to check, clutch gap, high side pressure, and not that I've ever seen this but low voltage to the clutch coil.

 

Did you read the link?

 

I did read the link, and thank you for that.
The one picture shows a a high side port on the hose block that attaches to the compressor. My port is on the low pressure side. I had to purchase a replacement hose block assembly to handle 134a and that is how it came, I don't know what the original was like.
The other picture shows a low pressure port on the VIR which is almost inaccessible. My car had this, but it was eliminated with the VIR eliminator kit..
I have no place to connect a high side port.

 

Then whomever advised you on how to convert to R134 mislead you. You can not correctly fill or diagnose issues with an AC system without a high side.
It's also unclear why you used a substitute for R134.

 

A few thoughts;
The clutch air gap should be set to .025" to .035" while disengaged
There should be a ground wire connected directly to the AC compressor mounting bracket
It needs 12 volts minimum when engaged with the blower on high speed, when checking voltage use the compressor ground at the compressor

You really need to know what the discharge pressure is along with the suction pressure to validate the system is functioning correctly.
I've seen the old A6 compressors run over 400 psi on the discharge without clutch issues

Neal

 

Thanks for your help. I really mean that.
I have to do something to get this working and it looks like the only avenue is to replace the refrigerant I have with 134.
I used the substitute refrigerant because 134 was banned and I thought this was the replacement.
I don't know how much damage I've done to the clutch

 

Thanks Neal , I don't have a ground wire from the compressor bracket yet, but I will install one and check the voltage.
I'm going to be switching to real 134 and hope that corrects my problems. As for the high side, nothing I can do without changing hardware ( again)

 

R134A is still readily available. It is banned from new car production.

 

I don't think your issues are from the refrigerant, but cant be sure without looking at the system in person. I've worked with hydrocarbon refrigerants and typically the head pressure is lower with them than r134a.

One other thing i would do is to spin the compressor by hand with the engine off and the clutch disengaged, your feeling for a smooth rotation (about 10 rotations). This should have been done prior to engaging the compressor clutch after installation to make sure there was no accumulation of oil in the cylinders.

I couldn't find instructions for the Old Air VIR eliminator kit, where did you install the orifice and where did you install the accumulator in relationship to the evaporator coil?

Did you connect the oil drain line to the orifice block and did you validate it was clear?

Neal

 

Sounds like it's locking up if the belt is tight, did you flush out the system ? If not contaminants from the old compressor may have ruined the new compressor

 

I tried to spin the compressor by hand today and can't budge it. Engine off clutch disengaged.
Clutch gap varies from roughly 15 to 25 thousandths. plates aren't parallel to each other.
The Old Air VIR eliminator kit , cycling clutch, connects directly to both sides of the evaporator. Very hard to get in, but you can't screw it up.
The oil drain line connects to the new high side aluminum block. but it is a blind hole. basically just capped.

 

Thanks for the pictures,
The compressor should spin over by hand, the fact that you can not spin it by hand could be an issue
The clutch air gap measurements are good so next check the voltage at the compressor and make sure your getting the correct voltage.

Neal

 

If you can't turn it by hand you have issue's internal inside the Compressor

 

seems if off , clutch has a gap.. and does not spin.. probably not a good sign for compressor.
Do they have Napa professional new? i even had to warrant one of them for a leak. i needed to show new parts like accumulator , etc..receipts which i had.
Maybe a refresh on exactly what you did when starting repairs in detail including
- what was in there before?
- was the correct oil used and previous oil removed?
- was accumulator replaced?
- if converting to 134 as mentioned.. stick to 134 only with proper oil..
- no clue on older c3 but does it have a screen? any debris?

if i had to do it all again and had compressor issue, i would go modern sanden compressor. box the old one if original is important.

wow..pricey for new

 

There is a nut on the end of the compressor shaft (hidden inside the clutch) that is used to retain the clutch once the gap is set, can you put a small ratchet and socket on it and get an idea of how much torque it takes to rotate it, be carful not to put excessive force and break/strip the nut or crank (the nut is torqued to 15 lb ft). The clutch is an interference fit to the crank snout so to much force to rotate the compressor can close the gap on the clutch. There are special tools required for proper servicing of the compressor and can usually be rented at the local parts house.

There should have been some paperwork with the compressor outlining how much oil was in the compressor and instructions on correct installation. The A6 has an oil sump and will hole around 6oz in the sump with the remaining oil in the condenser, lines, evaporator, accumulator/dryer, if you didn't clear all the components of the system and installed the compressor full of oil above the sump lvl amount you may have excess oil in the system. Excess oil will not prevent the compressor from turning by hand but could cause damage over time if left that way. On compressors that come with oil in them it is critical to spin them by hand, in shipping they can be inverted and left laying with the sump up allowing the oil to get into areas not intended for oil. When mounted the oil will drain to the sump and turning it by hand will facilitate allowing the oil to drain into the sump, these compressors will not pump liquid without damage over time depending how much liquid there is.

Neal