If you have an orifice tube system, then it is an accumulator on the low side. If it is an expansion device, then yes, it is a drier on the high side.
The condition of the oil would tell a story.
How do you get airflow across the condenser? Is it in front of the engine fan?
Need help with repairing 77' Airstream RV engine AC
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tony1963
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Re: Need help with repairing 77' Airstream RV engine AC
The A6 is a great compressor, just not what is light and compact in today's vehicles. If you have an A6, stick with it.
Ultimately you are going to have to determine if high pressure is locking the pump or lack of lubrication. I believe you will find that it is high pressure.
Ultimately you are going to have to determine if high pressure is locking the pump or lack of lubrication. I believe you will find that it is high pressure.
Re: Need help with repairing 77' Airstream RV engine AC
That's why I came here... What would be the cause of high pressure? how would I correct it?tony1963 wrote: ↑Tue Jun 27, 2023 2:42 pm The A6 is a great compressor, just not what is light and compact in today's vehicles. If you have an A6, stick with it.
Ultimately you are going to have to determine if high pressure is locking the pump or lack of lubrication. I believe you will find that it is high pressure.
I really have zero knowledge on solving AC problems. learning as much as I can from you guys!
thank you
Re: Need help with repairing 77' Airstream RV engine AC
I would recommend recovering the charge and again inspecting the system. As mentioned earlier, you are going to have to definitively determine if the compressor is seizing due to lack of lubrication or seizing due to high pressure.
I would also recommend doing your system flush again and yes, replace the drier assembly. Going back to the expansion device, that should be replaced and your evaporator flushed as well. A stuck expansion valve can also cause high pressure if it gets stuck closed.
I used 91% alcohol as a flush agent for years. Yes, it is flammable and you have to be careful, but it really cleans properly and does not create a hazmat condition. Be sure to vent afterwards with plenty of shop air to evaporate the residue.
Pull a vacuum for about an hour to make sure that you have boiled off all of the alcohol and water content. I have seen formulas before for oil charges on systems with the A6 compressor. There is always a certain base amount because the A6 has a sump and then you add from there based upon the system size.
Tell me again how many lbs of refrigerant your system holds?
I would also recommend doing your system flush again and yes, replace the drier assembly. Going back to the expansion device, that should be replaced and your evaporator flushed as well. A stuck expansion valve can also cause high pressure if it gets stuck closed.
I used 91% alcohol as a flush agent for years. Yes, it is flammable and you have to be careful, but it really cleans properly and does not create a hazmat condition. Be sure to vent afterwards with plenty of shop air to evaporate the residue.
Pull a vacuum for about an hour to make sure that you have boiled off all of the alcohol and water content. I have seen formulas before for oil charges on systems with the A6 compressor. There is always a certain base amount because the A6 has a sump and then you add from there based upon the system size.
Tell me again how many lbs of refrigerant your system holds?
Re: Need help with repairing 77' Airstream RV engine AC
"Tell me again how many lbs of refrigerant your system holds?"
4lbs of R12 which through an online a134 conversion chart came out to 48oz of a134?
Yes, I will strip and flush the system and report back. I won't have a chance to get back to it for a few weeks as its in storage while I am off working.
4lbs of R12 which through an online a134 conversion chart came out to 48oz of a134?
Yes, I will strip and flush the system and report back. I won't have a chance to get back to it for a few weeks as its in storage while I am off working.
Re: Need help with repairing 77' Airstream RV engine AC
I went back and reread your original post. I see that you see the high pressure spike to 275 psi and then the belt starts squealing. That tells me that the compressor is running, otherwise you wouldn't build that pressure.
Also, keep in mind that the surface area of a modern serpentine belt is 4-5X that of an old V belt so it does not take as much energy pushing against the compressor to make the belt squeal as it would on a modern vehicle.
Where I am going with this is that you likely have adequate lubrication but something is causing a temporary blockage that results in the high side pressure going very high. For that reason, you'll have to recover the system and figure out what kind of expansion device is in the evaporator. Also, follow the liquid line from the condenser back to the evaporator and see if you can find any kind of place an orifice tube might be hiding. Sometimes they are in that liquid line.
Also, keep in mind that the surface area of a modern serpentine belt is 4-5X that of an old V belt so it does not take as much energy pushing against the compressor to make the belt squeal as it would on a modern vehicle.
Where I am going with this is that you likely have adequate lubrication but something is causing a temporary blockage that results in the high side pressure going very high. For that reason, you'll have to recover the system and figure out what kind of expansion device is in the evaporator. Also, follow the liquid line from the condenser back to the evaporator and see if you can find any kind of place an orifice tube might be hiding. Sometimes they are in that liquid line.
Re: Need help with repairing 77' Airstream RV engine AC
OK, time to stop the guessing game.
A 1977 P30 has a TXV. Mounted at the evaporator. The A6 does not cycle in this system. The TXV throttles the refrigerant to prevent icing the evaporator
The A6 has an actual oil sump, and an oil pump. All of the oil goes in the compressor sump through the plug on the case before installation.
There is no accumulator to drain any oil out of. There is a Receiver Drier in the system. If the R/D was not changed when it was converted to R134a, the dryer dessicant may not have been compatible. The TXV could be clogged with dessicant or other debris.
275 psi is easy work for an A6. 375 psi is still within it's range. If it is locking up it is low on oil or has a mechanical failure. Turn the compressor clutch by hand and see what it feels like.
We are spoiled by decades of serpentine belts. V belts need significant tension to transmit power, and can become glazed and slip. A belt that looks fine, but is a few years old may slip and squeal. A belt without enough tension can do the same thing.
The A6 is still the best choice for this installation. Get the system broken down and clean. Replace the TXV - a new AC Delco part will be under 30 bucks.
Check the fan clutch on that 454. They wear out, and while the engine is not yet overheating the airflow over the condenser is suffering. If you notice a big difference in cooling between highway driving and stop & go traffic that is the first place to look.
A 1977 P30 has a TXV. Mounted at the evaporator. The A6 does not cycle in this system. The TXV throttles the refrigerant to prevent icing the evaporator
The A6 has an actual oil sump, and an oil pump. All of the oil goes in the compressor sump through the plug on the case before installation.
There is no accumulator to drain any oil out of. There is a Receiver Drier in the system. If the R/D was not changed when it was converted to R134a, the dryer dessicant may not have been compatible. The TXV could be clogged with dessicant or other debris.
275 psi is easy work for an A6. 375 psi is still within it's range. If it is locking up it is low on oil or has a mechanical failure. Turn the compressor clutch by hand and see what it feels like.
We are spoiled by decades of serpentine belts. V belts need significant tension to transmit power, and can become glazed and slip. A belt that looks fine, but is a few years old may slip and squeal. A belt without enough tension can do the same thing.
The A6 is still the best choice for this installation. Get the system broken down and clean. Replace the TXV - a new AC Delco part will be under 30 bucks.
Check the fan clutch on that 454. They wear out, and while the engine is not yet overheating the airflow over the condenser is suffering. If you notice a big difference in cooling between highway driving and stop & go traffic that is the first place to look.
Re: Need help with repairing 77' Airstream RV engine AC
In a broad sense of the word, everyone here responding to the thread is forced to "guess" as none of the respondents have physically inspected the vehicle.
Additionally, no one that I am aware has had any type of "tele-exam" with the OP. The information that is being provided is based upon symptoms and known complaints.
The issue of an expansion device and the serpentine belt vs V-belt have already been raised.
Additionally, no one that I am aware has had any type of "tele-exam" with the OP. The information that is being provided is based upon symptoms and known complaints.
The issue of an expansion device and the serpentine belt vs V-belt have already been raised.
Re: Need help with repairing 77' Airstream RV engine AC
Great advice, I will tear down inspect, flush and report back.
thank you
thank you