I learned something today about charging a vehicles AC system

[JimPghPA]

I learned something today about charging a vehicles AC system.

I knew to bleed air out of all of the hoses for the manifold set before connecting up to the car. But I was unaware that oil from the car's system would travel up into the high pressure hose while it was connected to the car.

When I went to disconnect the high side pressure hose from the manifold that I had bought recently from Harbor Freight from the high pressure port of the car I got a significant pop of refrigerant and oil. And then I realized that there was still significant pressure showing on the manifold after I had disconnected both the high and low from the car so I went to bleed the manifold and got a significant amount of oil from the manifold. I was surprised that this was oil and realized that while the manifold was connected to the high pressure port that the high pressure side had pushed a lot of oil from the car refrigeration system to the high pressure hose of the manifold. Had I known that this was going on I would have left the manifold connected to the car for a significantly long time so that the oil would have had time to return mostly from the manifold to the car after the pressures on the high side of the car had reduced, which would have taken some time but it would have happened. So this is something I'll keep in mind the next time I charge a vehicle with a manifold set.

When I first connected the manifold to the car and had the neighbor holding the RPM at 2,500 the high pressure was at 200 while the ambient Air Temperature was 87 Fahrenheit. I charged it until the high pressure was at a minimum of 225 and a maximum of 250 again while the neighbor was still holding the RPM in 2500. I'll be paying attention to how well it cools in the next week or so to determine whether I put enough refrigerant in it. The last thing I want to overcharge and have liquid get into the intake of the compressor and blow out the compressor. So I'm a little on the conservative side when I charge a system.

I'm a little bit concerned that now my refrigeration system has lost about an ounce of oil but it will probably be all right. I learned the lesson and the next time I charge a vehicle I will try to give it time for any of the oil that has gotten into the high pressure side hose to drain back out of the hose from the manifold into the car when the pressure inside the car AC system has dropped after sitting for a significant amount of time. Only after that amount of time has passed do I then disconnect a high pressure hose from a vehicle in the future.

 

[Chris142]

It's always better to add slightly too much oil than not enough. If you turn the high side valve off at the port then open the wheel knobs ( after turning the supply tank off or pinching the supply line off as to not add more refrigerant) it will suck what's in the high side into the low side and bring most of the oil in the line with it

 

[JimPghPA]

It's always better to add slightly too much oil than not enough. If you turn the high side valve off at the port then open the wheel knobs ( after turning the supply tank off or pinching the supply line off as to not add more refrigerant) it will suck what's in the high side into the low side and bring most of the oil in the line with it

I had just thought out that exact sequence and was about to post it and then I saw that you had posted it before I did. I had no idea that there would be oil in the high pressure side line. I had charged it completely through the low side only line. So any oil that was in the high side line had to have come from the vehicle and not from the charge can. I don't even know if the 12 oz charge can that Walmart sells has oil in it or not?


Last fall, Walmart had the 12 oz R134a cans marked down to $3 a can so I picked up 10 of them because my 2016 Honda CRV is a R134a system and I plan on keeping it for a very long time. This was the first time I had to charge it and I just recently purchased the Harbor Freight manifold system along with the little adapter for the self- resealing cans.


Back in the '70s I used to work for a Energy Research company and we did a lot of heat pump systems so I basically work as a electronic engineer and also a refrigeration Tech and I haven't forgotten anything about Refrigeration since then even though it's a whole new world with the refrigerants that they're using nowadays.

 

[mk378]

Most of what came out was liquid refrigerant, mixed with some oil. Properly distributed as it was, a small amount of oil can make a big mess and appear to be a lot more than it really was.

While taking measurements, liquid will condense in the high side hose as it is the coldest part on the high side. In order to return it to the system, use this disconnection procedure:
1. The yellow hose needs to be closed off-- either connected to a cylinder with its valve closed, or it is one of the better sets with a shrader valve built into the yellow hose to close the far end when not connected.
2. Close the high side coupler and disconnect the red hose from the car.
3. With the compressor running, open both valves on the manifold. The suction will clear everything in the manifold down to the low side pressure. Liquid cannot exist at that pressure.
4. Close the manifold valves then uncouple the blue hose from the car.

 

[zzyzzx]

What's even worse than losing that amount of oil, is when you then get a bunch of dye all over the place as well.

 

[cptbarkey]

I had just thought out that exact sequence and was about to post it and then I saw that you had posted it before I did. I had no idea that there would be oil in the high pressure side line. I had charged it completely through the low side only line. So any oil that was in the high side line had to have come from the vehicle and not from the charge can. I don't even know if the 12 oz charge can that Walmart sells has oil in it or not?


Last fall, Walmart had the 12 oz R134a cans marked down to $3 a can so I picked up 10 of them because my 2016 Honda CRV is a R134a system and I plan on keeping it for a very long time. This was the first time I had to charge it and I just recently purchased the Harbor Freight manifold system along with the little adapter for the self- resealing cans.


Back in the '70s I used to work for a Energy Research company and we did a lot of heat pump systems so I basically work as a electronic engineer and also a refrigeration Tech and I haven't forgotten anything about Refrigeration since then even though it's a whole new world with the refrigerants that they're using nowadays.

why did you need to recharge it? perhaps there was an issue with a port valve core leaking and it still exists?

 

[Kurtatron]

This is so confusing. Why are you waiting for oil to go back into the AC system on the high side? You only ever charge ac systems on the low side. High side is only for checking pressure, not adding anything. High side shouldn’t fill with oil and fluid as you charge the system.

“When I went to disconnect the high side pressure hose from the manifold that I had bought recently from Harbor Freight from the high pressure port of the car I got a significant pop of refrigerant and oil.”