AC charging question

[Mheiron]

So I restored the AC system on the 69 Charger myself. I brought in an AC technician to check it out and charge it up.

So last weekend we pressure and vacuum tested the system. Everything is new or rebuilt. The system tested so no leaks once I found good quality R134 adapters and the right O rings. The system was built to accept R134

We charged up the system and got the high side pressure up to 130 psi but the suction pressure was zero!. We checked and found the evaporator full of oil. It was probably shipped that way so we blew it out dry and tried again but got the same result.

We’re thinking the expansion valve is too small and we need a bigger one. Any other ideas?

 

[davek]

When I did mine on my 74 challenger I replaced the o rings to green ones, new dryer and filled it with r134/ Remember r134 is not the same amount its less then the factory freon amount. I had no problems .and it worked great. All stock Thats all I have,hope someone can help you out.

 

[pnora]

Was the low side creating a negative below zero reading?

 

[threewood]

Are you sure the service manifold valve was open and/or depressing the schrader valve?

 

[Mheiron]

I think I remember the pressures equalized when we turned the car off.
The low side pressure was zero with car running

 

[pnora]

Are you sure the service manifold valve was open and/or depressing the schrader valve?

With the system shut off and setting for a few minutes the pressures will equalize. If it does that the service port and gauge would be ok and working.

 

[Demonic]

Maybe the exp. valve is bad or clogged. I'm assuming the filter/dryer is new?

 

[qkcuda]

While on the subject, can you use the same expansion valve for the R134 as you did for R12? I have a brand new spare and I had to take my system apart during the engine swap, so I will be converting to R134 or whatever they are using these days.

 

[Sixpactogo]

When I built my 68 with the 6.1 engine, I used the compressor that came with the 6.1. Installed a new stock condenser, dryer and expansion valve. Once the underhood plumbing was complete, it was charged with the R134. It has been flawless since 2016 with no recharges or leaks. That said, I believe your expansion valve is the problem but I don't think there is any reason to need a special valve. Just a new one.

 

[WileE]

Let me get this straight..... You replaced ALL components ? You then pulled vacuum on the system. It held vacuum. You charged with R134. Then you found the evaporator core full of oil ?

 

[RJRENTON]

When I built my 68 with the 6.1 engine, I used the compressor that came with the 6.1. Installed a new stock condenser, dryer and expansion valve. Once the underhood plumbing was complete, it was charged with the R134. It has been flawless since 2016 with no recharges or leaks. That said, I believe your expansion valve is the problem but I don't think there is any reason to need a special valve. Just a new one.

The TXV (Thermostatic Expansion Valve) is an extremely important component of the refrigerant system. It meters the liquid refrigerant into the Evaporator based on exiting outlet temperature of the Evaporator plus a calibrated amount of SUPERHEAT, to insure no unevaporated refrigerant gets back to the compressor. The TXV calibration is based on the specific heat characteristics of the refrigerant used......to reiterate your comment.....it's a special Valve with special calibration points. Thermodynamics is an exact science...correct componens are necessary for correct operation.........just my opinion....
BOB RENTON

 

[Mheiron]

Yes everything is new. The dryer is new the expansion valve was a stock replacement new from Four Seasons. The system held 100 psi and full vacuum before and after we blew oil from the evaporator. We added R134 before and after we blew out the evaporator. We have a new/larger expansion valve to try next.

 

[RJRENTON]

1

Yes everything is new. The dryer is new the expansion valve was a stock replacement new from Four Seasons. The system held 100 psi and full vacuum before and after we blew oil from the evaporator. We added R134 before and after we blew out the evaporator. We have a new/larger expansion valve to try next.

Out of curiosity, how much oil did you drain/blow out from the Evaporator? The entire system, including the compressor is about 11-14oz of polyoil for R134A refrigerant. Oil travels with the refrigerant and bulk of it tends to collect in the dryer and compressor crank case, the balance of oil is spread throughout the system.....too much oil is as bad as too little oil. Sometimes the TXV is cross connected or pressure balanced to the Evaporator outlet beside, being connected to the Evaporator for temperature and superheat control......depends on the valve........just my opinion....
BOB RENTON

 

[Sixpactogo]

.....to reiterate your comment.....it's a special Valve with special calibration points. Thermodynamics is an exact science...correct componens are necessary for correct operation.........just my opinion....
BOB RENTON

I don't know if you are trying to educate me on the workings of AC or not but I do know the importance of the components that make up the workings of an air conditioner. Just to reiterate your comment of it being a special Valve with special calibration points. I used a factory 1968 Mopar designed expansion valve for R12 in my 68 Charger and charged it with R-134 back in 2015. There was nothing special done to it and it has been doing it's job for 10 years. There are tons of others out there that have converted R-12 to R-134 using an expansion valve that was designed for R-12. That is not an opinion. It is fact.

 

[RJRENTON]

I don't know if you are trying to educate me on the workings of AC or not but I do know the importance of the components that make up the workings of an air conditioner. Just to reiterate your comment of it being a special Valve with special calibration points. I used a factory 1968 Mopar designed expansion valve for R12 in my 68 Charger and charged it with R-134 back in 2015. There was nothing special done to it and it has been doing it's job for 10 years. There are tons of others out there that have converted R-12 to R-134 using an expansion valve that was designed for R-12. That is not an opinion. It is fact.

I guess you've heard of the DFL factor. The calibration points of the controlling TXV's can be significant enough to flood or starve the evaporator.....the capillary bulb strapped to the evaporator outlet piping that controls the valves operation and the internal orifice is the difference....not changing the valve is OK as long as you're happy with the operation......which is good but not as good as it could be.....what's the air temperature and pressures coming off the evaporator at wort case conditions...???? Only suction temps and pressures, compressor discharge pressures depends on ambient temp and engine RPM. R134A has totally different operating pressures than R12. Btw....the new refrigerant is R1234YF used in the new cars.....fyi.......R134A is being phased out........
BOB RENTON

 

[Jim Kent]

I would try adding more gas did you measure when adding gas? R134 pressure temperature chart high side with 70 deg ambient should be 145-160psi with 35-40psi suction low side and if 90 deg outside high side pressure 250-270psi with 45-55psi low side. Pressure temperature chart is gold standard or baseline with troubleshooting AC sounds like you may not condensing enough liquid. I like to have floor fan blowing at front and engine at 2000-2500 rpm when charging, measure air discharge coming out of vents 40 degs. Suction line temperature before compressor should be cold 10-20 deg warmer than evaporator temp/pressure example 35psi low side pressure is equal to 40deg evp so you should have 50 to 60deg suction line temp (superheat) so you don't have liquid returning to compressor that would cause catastrophic compressor failure. Example would be about 40deg discharge air from vents. Lots of variables but numbers should be close

 

[Charrlie_S]

First off, what compressor are you using? Where are you maesuring the low side pressure? How much refrigerant have you put in? Are you using the cast iron RV-2 compressor? does it have a EPR valve in the suction port? If it does and you are measuring the suction pressure at the cyl head, it is very possible the system is either still low on charge, or the EPR valve is stuck shut. Your AC tech should be able to determine if there is blockage in the system just by feeling the lines and compareing temps of the lines/components. It looks like you have had new hoses made up, it is possible the is a blockage in one of the hoses. Hate to say it but one time I tore my hair out tring to find a blockage, and it turned out one hose had a "mud dobbers" nest in it. My own fault I neglected to cap one end of the hose while it was on the shelf. Another time we found a plastic cap pushed inside the hose from the factory.
It is not likely that your problem is the expansion valve being too small. It could be stuck shut.
PS: I looked back at your pics. You do have a RV-2 compressor, and it looks like you are probably using the port on the cyl head. I looked at my manuals to refresh my memory. 69 Charger should have an EPR valve in the suction fitting at the rear of the compressor. The should be a gauge connection at the fitting at the back of the compressor. The is where you should hook up a gauge to check suction (low) side pressure. If you use the gauge port on the cyl head and the system is low on charge you will get the results you are getting. In normal operation pressure at the fitting on the rear of the compressor will generally be higher than the fitting on the head.

Can you post a picture of the expansion valve and how/where the small copper lines are connected? I can't make it out on the pic you posted.

 

[savoy64]

First off, what compressor are you using? Where are you maesuring the low side pressure? How much refrigerant have you put in? Are you using the cast iron RV-2 compressor? does it have a EPR valve in the suction port? If it does and you are measuring the suction pressure at the cyl head, it is very possible the system is either still low on charge, or the EPR valve is stuck shut. Your AC tech should be able to determine if there is blockage in the system just by feeling the lines and compareing temps of the lines/components. It looks like you have had new hoses made up, it is possible the is a blockage in one of the hoses. Hate to say it but one time I tore my hair out tring to find a blockage, and it turned out one hose had a "mud dobbers" nest in it. My own fault I neglected to cap one end of the hose while it was on the shelf. Another time we found a plastic cap pushed inside the hose from the factory.
It is not likely that your problem is the expansion valve being too small. It could be stuck shut.
PS: I looked back at your pics. You do have a RV-2 compressor, and it looks like you are probably using the port on the cyl head. I looked at my manuals to refresh my memory. 69 Charger should have an EPR valve in the suction fitting at the rear of the compressor. The should be a gauge connection at the fitting at the back of the compressor. The is where you should hook up a gauge to check suction (low) side pressure. If you use the gauge port on the cyl head and the system is low on charge you will get the results you are getting. In normal operation pressure at the fitting on the rear of the compressor will generally be higher than the fitting on the head.

Can you post a picture of the expansion valve and how/where the small copper lines are connected? I can't make it out on the pic you posted.

First off, what compressor are you using? Where are you maesuring the low side pressure? How much refrigerant have you put in? Are you using the cast iron RV-2 compressor? does it have a EPR valve in the suction port? If it does and you are measuring the suction pressure at the cyl head, it is very possible the system is either still low on charge, or the EPR valve is stuck shut. Your AC tech should be able to determine if there is blockage in the system just by feeling the lines and compareing temps of the lines/components. It looks like you have had new hoses made up, it is possible the is a blockage in one of the hoses. Hate to say it but one time I tore my hair out tring to find a blockage, and it turned out one hose had a "mud dobbers" nest in it. My own fault I neglected to cap one end of the hose while it was on the shelf. Another time we found a plastic cap pushed inside the hose from the factory.
It is not likely that your problem is the expansion valve being too small. It could be stuck shut.
PS: I looked back at your pics. You do have a RV-2 compressor, and it looks like you are probably using the port on the cyl head. I looked at my manuals to refresh my memory. 69 Charger should have an EPR valve in the suction fitting at the rear of the compressor. The should be a gauge connection at the fitting at the back of the compressor. The is where you should hook up a gauge to check suction (low) side pressure. If you use the gauge port on the cyl head and the system is low on charge you will get the results you are getting. In normal operation pressure at the fitting on the rear of the compressor will generally be higher than the fitting on the head.

Can you post a picture of the expansion valve and how/where the small copper lines are connected? I can't make it out on the pic you posted.

First off, weigh the proper charge in. This will eliminate any confusion over whether or not you have too much or to little charge. Place a blower fan in front of car and operate car at 2000_2500 rpm as stated previously. If you still have the pressures indicated previously then you have either a bad expansion valve or a restriction in the system.

 

[RJRENTON]

First off, weigh the proper charge in. This will eliminate any confusion over whether or not you have too much or to little charge. Place a blower fan in front of car and operate car at 2000_2500 rpm as stated previously. If you still have the pressures indicated previously then you have either a bad expansion valve or a restriction in the system.

What you state is from the FSM including the recommendation of the fan in front of the condenser coil. Personally, whenever I charge, just topping off refrigerant or from empty, I charge to get air off the evaporator coil to 34°-36° F to prevent icing with circulation fan on high with windows open....for max heat load simulation. I do not monitor compressor discharge pressure. But...everyone has their own techniques.......
BOB RENTON

 

[Charrlie_S]

What you state is from the FSM including the recommendation of the fan in front of the condenser coil. Personally, whenever I charge, just topping off refrigerant or from empty, I charge to get air off the evaporator coil to 34°-36° F to prevent icing with circulation fan on high with windows open....for max heat load simulation. I do not monitor compressor discharge pressure. But...everyone has their own techniques.......
BOB RENTON

Do you keep adding refrigerant untill you get to 34-36 degrees? what if you get to 40* and it doesn't go lower? Even if you get to 36* the head pressore could go to 300+ lbs. I have seen systems so over charged by DIY people the belt burned off the clutch with the hi side over 400 lbs. You are aware that with 134a the correct charge is actually Charge to about 75 % of the proper r-12 charge, then add a little more at a time allowing the system to stablize and watch the suction temp. keep adding untill the temp stops droping, and starts to increase, then remove about 1-2 OZ of refrigerant. With 134a it is better to be slightly under charged than over charged. R-12 was a lot more forgiving aboutb over charge.
PS: with a system with an EPR the chances have getting the evap air temp down to 34-36 degrees ain't gonna happen. The car in question "should" have an EPR valve.