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