Replacing AC System Oil

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My Wife's Dacia has a very slow AC system leak and has done since we bought it 18 months or so ago. If topped up, it seems to last around 6 months before the A/C stops working.

We initially had the system vacuumed and gassed by a local specialist in February 2021.

In July 2021 the system was starting to get a bit tired so I topped it up using a canned top-up.

In October 2021 the radiator sprung a leak, and while repairing I noticed the condenser was in a bad way and all the fins were rotting out. I replaced the condenser and two service valves and had a specialist vacuum and gas up the system again.

Earlier this year the system stopped working again. I'm planning on topping it back up but including a UV dye this time to try and really hone down on where the system is leaking. I may just use an in-can system and DIY it again. We'll see. I note that STP do a top up kit that includes a UV dye.

Anyway, the main reason for this thread is the oil in the system. The compressor is a little coarse sounding, but when gassed up otherwise works perfectly fine. I'm wondering if the compressor is low on oil? How easy is it to drain the system down and re-install fresh oil?
 
You need to replace all your components to replace all the oil. Evap, condenser, compressor, accumulator/dryer. Oil is hydroscopic and thus a desiccant to your system. Since you've had the system open a few times, I'd start to worry about moisture. You can try adding about 2oz of UV dye/oil, don't go overboard, too much oil will be bad for the system too.
 
When the condenser went bad, did you also replace the other parts like compressor, dryer, orifice, etc?
or at least flush the system?

When a component in AC system goes bad and leaking, a lot of contaminants went in and that needs to be clean out.
If not, they will just recirculate and cause other issue like ruining the compressor, etc.
Also, there are o-rings in all the pipe connectors that needs replacing when opening the system.
 
When the condenser went bad, did you also replace the other parts like compressor, dryer, etc?

The condenser didn't really go bad. It was just in a rough shape. The fact the leak seems to have remained after replacing the condenser, it seems to me that the condenser itself was actually air-tight.

I have only replaced the condenser.
 
You can also use sniffer to see the leak.
May be try a mechanic who have that tool.

First check to see if there is still any pressure in the system.
If not, then there are leaks definitely.
If you recharge it, it is just wasting money.
You need to fix it first.
 
You can also use sniffer to see the leak.
May be try a mechanic who have that tool.

First check to see if there is still any pressure in the system.
If not, then there are leaks definitely.
If you recharge it, it is just wasting money.
You need to fix it first.

Would a sniffer pick up a leak that's taking 6 months to deplete to a level where the A/C doesn't work? That's an awfully small leak. That was the only reason I was going to hedge my bets with a UV dye.
 
Small leaks at the shaft seal can be really hard to find. I recommend using one of those 100 LED UV lights with the special glasses after dark to look for leaks.
 
I’d open everything I could, change all o rings I could access, consider replacing the receiver/dryer and the compressor if you think it’s suspect, and then refill the components with the right amount per the Factory Manual. It should give quantities per component.
 
I was taught that the dessicant has already absorbed moisture while on the assemby line and/or while doing any repairs there after. Furthermore, I used nitrogen for leak detection and used to add at least 2oz. of make up oil plus an extra ounce for the drier.
 
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Depending on how system was vacuumed (how deep the vacuum and the length of time the vacuum was allowed to "work"), desiccant should be okay (as long as system wasn't open to the environment for weeks and weeks). NONETHELESS, it is not expensive and once your leaks are fixed changing the desiccant is a great idea.

With the current parts shortages - if system is open just cap the lines after filling with nitrogen (displaces the water laden air). Not perfect but works until the parts come in and then system can be vacuumed and observed for "loss".

The vacuum is to evaporate the moisture as the water in the system will "boil" off in the vacuum. If the system will hold vacuum for 30 minutes with no change, it is most likely okay to reuse the desiccant (dryer, accumulator, etc). HOWEVER, if you have the slightest leak this will never work as the system won't hold.

A vacuum test IS NOT SUITABLE to find leaks. The system runs with pressures that greatly exceed what a vacuum can test for and should be tested with nitrogen at normal pressures.)

R134a, depending on ambient temperature and humidity, should be around 70 psi static and should hold that for days with no loss. If you lose any at all, it's time to start with the easy stuff if you have no dye or sniffer available. Valves, seals, etc.

You must fix the leak first. It is clear your system is losing refrigerant, so that should be job one.
 
Just wanted to update this.

The dryer is built into the condenser so would have been replaced when I replaced the condenser.

I bought an A/C Pro R134A canned top up that seems to suggest it contains a lubricant, but nothing about a dye.


The car is actually a R1234YF system but I used an adaptor to install the R134A 'top-up' gas into the system.

Interestingly, the system still had a fair amount of pressure. It required only a 5 second 'press' of the trigger to bring the pressure up to the 'filled' marker and make the system fully operational again.

I held the can upside down while charging hoping to get as much of the lubricant into the system as I possibly could.

The compressor is now totally silent other than the 'clack' of the clutch kicking in and out. The coarse gravelly sound we had from the compressor has gone away completely so I'm pretty confident we are low on oil.

I'll purchase some oil and some dye. I think the best way to get it into the system is to pour it into the charge hose and push it into the system with a small amount of charge.
 
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