A/C pressures

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Demonic said:
But the condenser is removing the latent heat from the refrigerant. That's how it got it's name.:lol:


Sorry, couldn't resist. Carry on. I'm staying out of this one.
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LOL yeah, but if you have humidity inside the system, you have bigger problems!!
 
512Stroker said:
Mike you right
My system will only cool down to 50*F at the vents. That's way I was looking for pressures.
All the charts I found were for R-12 my has been converted to 134A
I thought this may make a difference, it didn't.
I going to dig in to today with a real set of gauges at a Buddy's shop.
I will report back
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Does the temp. drop when going down the road or when you rev the engine? Also, is the suction line at the compressor cold or sweating?
 
93ragtop said:
Does the temp. drop when going down the road or when you rev the engine? Also, is the suction line at the compressor cold or sweating?
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Vent temp stay constant.
Suction line does sweet
 
I would try misting the condenser with water. If the evap. temp. drops (inside) Then IMO its either overcharged, the condenser is too small, or (and not likely) not getting enough air across the condenser. By it not changing going down the road, pretty much rules that out, again, IMO

If none of that changes, I would suspect a weak compressor.
 
If you suction line is sweating that usually means you are pretty close to optimum on charge. I would look into gaskets and vacuum door travel in the ac box. Could be air leakage. When I rebuilt mine it was full of leaves and door gaskets were completely gone.
 
93ragtop said:
I would try misting the condenser with water. If the evap. temp. drops (inside) Then IMO its either overcharged, the condenser is too small, or (and not likely) not getting enough air across the condenser. By it not changing going down the road, pretty much rules that out, again, IMO

If none of that changes, I would suspect a weak compressor.
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Ugh. This must be what it's like to be addicted to something. Ideally, you want a consistant 37* evaporator. IF the metering valve is correctly set (or sized in the event of a non-adjustable metering device ) it shouldn't be hard to achieve. In original Chrysler systems (except A bodies ) there was an Evaporator Pressure Regulator at the inlet of the compressor. This did two jobs - maintaining a nearly perfect evap temp and preventing liquid slugging at low loads. The original system was sized based on a steady flow of liquid at the metering valve inlet. Long story short, change the metering valve (TXV) if you're going to 134a.

I'm not a fan of PAG oil for 134a conversions. I've seen it clump up in commercial systems that were immaculate. Ester oil is readily available at most auto part chains, and is more tolerant of mineral oil traces left in the bottom of the coils, filter-dryer and compressor.
 
512Stroker said:
I have an all stock component 1967 factory A/C system that has been converted to 134A
What pressures on both the high and low side should I be getting when the system is operating properly?
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Well the verdict is in.
80* ambient
45 psi - low side
145 psi - hi side
52* air at the evaporator
The old reman compressor is weak.
I did not do the 134A conversation so I have no idea what , when and/or with what was done.
 
Well at least you have it figured out.
Personally, if it was mine, assuming you can find a compressor, I would blow it out, flush as much as you can, replace the drier, and as someone said above, use ester oil. If everything is stock, if possible weigh the charge in.... I think its recommended to use 18%? less with 134a. but check those numbers.
Good luck and look forward to hearing if you get it fixed.
 
93ragtop said:
Well at least you have it figured out.
Personally, if it was mine, assuming you can find a compressor, I would blow it out, flush as much as you can, replace the drier, and as someone said above, use ester oil. If everything is stock, if possible weigh the charge in.... I think its recommended to use 18%? less with 134a. but check those numbers.
Good luck and look forward to hearing if you get it fixed.
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Thanks for the come back.
I am going to use it as is, as I dont want to gut the thing during the middle of the summer. Plus the $ money end of it sucks.
The car is not even near original so I was thinking of a Vintage Air type system with some king of low mount compressor brackets.
 
512Stroker said:
Well the verdict is in.
80* ambient
45 psi - low side
145 psi - hi side
52* air at the evaporator
The old reman compressor is weak.
I did not do the 134A conversation so I have no idea what , when and/or with what was done.
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Not bad numbers. What does it cool to out on the road turned down low. If that temp is down in the mid to high 30° range you don't need any more freon. If the temp under those conditions is still in the mid 40° range you might sneak a small shot of 134. You might get another 5° out of it without going too far. You don't want to freeze it up.
 
I have found a better rule of thumb for R134a conversions is a high-side pressure of 2.2 to 2.5 times the ambient air temp at the front grille in deg.F. So on a 90F day, 200 to 225 psi. Agree with the observation that the return line should be sweating all the way back to the compressor.

I have also had success using "Enviro-Safe" (mixture of propane and butane) in both R12 and R134a systems. The advantage there is that a solvent flush and complete oil change is not required. But it's illegal in 17 states (the last I checked) due to lobbying and scare tactics by MACS who want their members to stay busy... Notice that R134a is now phasing out and getting more expensive in favor of a new patented incompatible refrigerant. Meanwhile the rest of the world continues to use hydrocarbons without daily fireball explosions.
 
Demonic said:
But the condenser is removing the latent heat from the refrigerant. That's how it got it's name.:lol:


Sorry, couldn't resist. Carry on. I'm staying out of this one.
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There won't be anything to stay out of. I don't argue anymore. I just throw it out there and if somebody disagrees or doesn't like it, then that's how it is. I've been doing A/C work on cars since about 1977, so I'm just throwin out what I've experienced.
 
Demonic said:
I'm not a fan of PAG oil for 134a conversions. I've seen it clump up in commercial systems that were immaculate. Ester oil is readily available at most auto part chains, and is more tolerant of mineral oil traces left in the bottom of the coils, filter-dryer and compressor.
Click to expand...

How about alkylbenzene (AB) oil? It is compatible with CFC and HCFC (and of course HC) refrigerants...
 
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