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Air Conditioning help needed.

mopar_71

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Hey all,
Im working on getting our 72 satellite Sebring plus to have AC again.
Originally it had it until the PO removed everything. I bought a donor car for the brackets, hoses, evaporator, condenser and compressor.

Flushed everything out, got new green seals, dryer and bulb type expansion valve.
Compressor had a spun piston bearing.
Got a rebuilt compressor off evil bay and had to send it back due to the shaft seal leaked.
Rebuilt the heater box while in there.
Took the EPR valve out of the compressor.
I put PAG 100 oil with UV dye in the compressor fill port.
Put everything together, pulled a vacuum and the next day, it was still holding.
Pulled vacuum again for about three hours before introducing R134a into the low side.

With the engine running, AC set to max, started filling the low side system and saw the clutch pull in. So the pressure switch works.
Added a total of 42 ounces or 2.6 pounds. As I was filling I noticed the low side pressure get to around 40 and high pressure around 275. It was around 50 deg F outside, if that matters.


Here‘s the issue I’m having.
No cold air.
The low side pressure drops to zero and the high side goes up to 285 or more Only when the compressor is on.
When the compressor is off, the low side pressure slowly builds up to 40 again.

I’ve bypassed the heater lines to be sure no hot water going into heater.
I’ve cycled the compressor off/on manually to prevent frosting of the evaporator.
The expansion valve “bulb” is inserted into the low side sheath and line has insulation on it.
The dryer does not have a sight glass.
My gut feeling is it needs more Freon but, I’ve already put a lot in it.

Anybody have some insight to this issue described?
Thanks for your time and answers in advance.
 
Hey all,
Im working on getting our 72 satellite Sebring plus to have AC again.
Originally it had it until the PO removed everything. I bought a donor car for the brackets, hoses, evaporator, condenser and compressor.

Flushed everything out, got new green seals, dryer and bulb type expansion valve.
Compressor had a spun piston bearing.
Got a rebuilt compressor off evil bay and had to send it back due to the shaft seal leaked.
Rebuilt the heater box while in there.
Took the EPR valve out of the compressor.
I put PAG 100 oil with UV dye in the compressor fill port.
Put everything together, pulled a vacuum and the next day, it was still holding.
Pulled vacuum again for about three hours before introducing R134a into the low side.

With the engine running, AC set to max, started filling the low side system and saw the clutch pull in. So the pressure switch works.
Added a total of 42 ounces or 2.6 pounds. As I was filling I noticed the low side pressure get to around 40 and high pressure around 275. It was around 50 deg F outside, if that matters.


Here‘s the issue I’m having.
No cold air.
The low side pressure drops to zero and the high side goes up to 285 or more Only when the compressor is on.
When the compressor is off, the low side pressure slowly builds up to 40 again.

I’ve bypassed the heater lines to be sure no hot water going into heater.
I’ve cycled the compressor off/on manually to prevent frosting of the evaporator.
The expansion valve “bulb” is inserted into the low side sheath and line has insulation on it.
The dryer does not have a sight glass.
My gut feeling is it needs more Freon but, I’ve already put a lot in it.

Anybody have some insight to this issue described?
Thanks for your time and answers in advance.
It will have to have a switch installed to cycle the compressor. Having said that, feel the hoses the high side should be hot the low side should be cold. I sounds like you might have a restriction, or blockage in one of the hoses. Which you can usually find were by feeling the hoses, if the restriction is on the high side lines it will get cold at the restriction. A restriction on the low side it will get slightly warmer after the restriction. Low side should get cold enough to frost, and the high side warm enough you don't want to hold on to it for very long. Since it is cooler this time of year maybe not quite that extreme but you get the idea. But the low side dropping to zero is the clue for a restriction.
 
Low ambient will give low pressures, but I agree with Rebelrouser above, You are restricted either at the filter/dryer or the TXV. 37-40 psi low side.

Oh, if you have a door out of place or no airflow across the evap, you may get low low side pressure. Check the box dampers and airflow, fan on high, etc.
 
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It will have to have a switch installed to cycle the compressor. Having said that, feel the hoses the high side should be hot the low side should be cold. I sounds like you might have a restriction, or blockage in one of the hoses. Which you can usually find were by feeling the hoses, if the restriction is on the high side lines it will get cold at the restriction. A restriction on the low side it will get slightly warmer after the restriction. Low side should get cold enough to frost, and the high side warm enough you don't want to hold on to it for very long. Since it is cooler this time of year maybe not quite that extreme but you get the idea. But the low side dropping to zero is the clue for a restriction.
You got me thinking on that. There is a thimble sized screen type filter on the outlet of the low side of the compressor. This filter fits inside the hose fitting that mounts to the back of the compressor.
It’s also the location of the spring and EPR valve that I removed.
I wonder if that’s the restriction.
Thanks for the reply Rebelrouser.
 
Restriction on the low side. Possible expansion valve.
 
What is the function of the epr valve in the compressor and why was it removed? can it function without it? If that doesn't matter I'd say your expansion valve is defective or there may be a restriction in the system. If anything was completely blocked you would pull into a vacuum.
 
What is the function of the epr valve in the compressor and why was it removed? can it function without it? If that doesn't matter I'd say your expansion valve is defective or there may be a restriction in the system. If anything was completely blocked you would pull into a vacuum.
The EPR (Evaporator Pressure Regulator) valve is NOT USED WITH THE R-134A REFRIGERANT.....AND is removed from the OEM RV2 Compressor suction inlet. IF using the R12 refrigerant, it is required.
The purpose of the EPR valve is to maintain a reasonably constant refrigerant suction pressure to prevent evaporator icing during high humidity low temperature operation......holds Evaporator Pressure at abt 36-38 psi. Works in conjunction with the expansion valve to control refrigerant superheat temperature.. R-134A has different operating characteristics. Justmy opinion of course.....
BOB RENTON
 
The EPR (Evaporator Pressure Regulator) valve is NOT USED WITH THE R-134A REFRIGERANT.....AND is removed from the OEM RV2 Compressor suction inlet. IF using the R12 refrigerant, it is required.
The purpose of the EPR valve is to maintain a reasonably constant refrigerant suction pressure to prevent evaporator icing during high humidity low temperature operation......holds Evaporator Pressure at abt 36-38 psi. Works in conjunction with the expansion valve to control refrigerant superheat temperature.. R-134A has different operating characteristics. Justmy opinion of course.....
BOB RENTON
Any info or link to the expansion valve needed to switch the compressor on/off?
I have the stock type and think this is 1 of the theories of low side pressure problem.

After a few hours of it sitting with the engine off, I checked the low and high side pressures again.
Both were equal. Does this mean I have a bad compressor? Is one cylinder low and one cylinder high? I might be over thinking that the left side cylinder(low side) isn’t creating pressure and when the compressor is switched off, the high side is leaking by….
 
Pressures will equalize with the compressor off after a while.
 
What is the function of the epr valve in the compressor and why was it removed? can it function without it? If that doesn't matter I'd say your expansion valve is defective or there may be a restriction in the system. If anything was completely blocked you would pull into a vacuum.
EPR valve was to throttle the flow of refrigerant to keep the evaporator from freezing up. these systems did not cycle the compressor but ran all the time. To my knowledge nobody makes an EPR that is compatible with 134A refrigerant.
 
Any info or link to the expansion valve needed to switch the compressor on/off?
I have the stock type and think this is 1 of the theories of low side pressure problem.

After a few hours of it sitting with the engine off, I checked the low and high side pressures again.
Both were equal. Does this mean I have a bad compressor? Is one cylinder low and one cylinder high? I might be over thinking that the left side cylinder(low side) isn’t creating pressure and when the compressor is switched off, the high side is leaking by….
The expansion valve meters the liquid refrigerant entering the Evaporator. The "old" system (origional) used a cross connected TXV by being connected to monitor suction pressure (connected to the suction line) AND temperature of the exiting refrigerant (Thermostatic bulb physically attached to the exiting suction line and insulated ro prevent underhood temp influence). The TXV DETERMINES THE DEGREE OF SUPERHEAT.
OVER the years, the system was simplified by eliminating the EPR vslve, and using a fixed orifice in lieu of the TCV and substituting a pressure switch that cycles the compressor on/off to maintain an average evaporator pressure of approximately 36-38 psi (approximately 38° F temperature).
The original Chrysler RV2 is a 2 cylinder machine....both cylinders work together or parallel operation not low pressure high pressure
There are several TXV selection sites as well as info on the pressure cycling switch. Their fittings must your existing connections using new compatible O-rings. Remember to install a new dryer and to EVACUATE THE SYSTEM for a few hours b4 recharging.
It is normal to have the high side/low side pressures be the same after overnite.....but pressures are dependent on surrounding temperatures.....Boyle's Law. Hope this helps your understanding.....do you have a FACTORY SERVICE MANUAL? A great source of information......
BOB RENTON
 
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You may still have moisture in the system.
 
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