Refilling AC Systems

[dlundblad]

The condenser in the Jeep needs replaced. I am so thankful it's winter so I can somewhat put this off.

How will I know how much refrigerant and oil (if any) to put back into the system? I bought a nice set of gauges as well as a vacuum pump. Can anyone think of anything else I'll need?

Thanks.

 

[mk378]

There should be a label with the amount of refrigerant for a full charge. Or check the service manual. You would add little if any oil, just enough to coat the inside of the new condenser, like an ounce.

The drier should be replaced any time a system leaks down to zero. If the condenser has a big hole and the pressure has been at zero with the hole open, there could be water contamination. Refrigerant oil used with R-134a absorbs water and becomes ineffective.

 

[kschachn]

The FSM for your car should list oil amounts for each component in the system.

And yes on the accumulator or dryer replacement.

 

[dlundblad]

So would the correct amount be of refrigerant be in PSI measured with a gauge or pounds measured with a recharge scale?

I bought the drier, condenser, gauges and pump.

 

[DBMaster]

It might pay to do a little research since there is a temperature/pressure curve that helps determine the appropriate refrigerant pressure based upon ambient temperature. I generally used a gauge set that indicated the appropriate range for the type of refrigerant being used in conjunction with a thermometer in my center vent register. Once I hit the bottom of the pressure range I looked for the vent temperature to bottom out at its coldest point and stopped filling. With refrigerant more is not better.

 

[The_Eric]

I show 27oz of R134 and 5oz of PAG 46.

If replacing parts, you should distribute the oil throughout the system.

 

[mk378]

Always measure refrigerant by weight when charging into an empty system. The only way to know for sure you have the proper charge is to start from empty (vacuum) and put in the specified amount by weight.

 

[Chris142]

Originally Posted By: mk378
Always measure refrigerant by weight when charging into an empty system. The only way to know for sure you have the proper charge is to start from empty (vacuum) and put in the specified amount by weight.
x2. Lots of shops still try to do it the hard way with varying degrees of success. A few ounces off and you will burn up the compressor.

 

[Trav]

Put 2 12oz cans in (make sure the get the pure refrigerant not with oil in it) that gives you 24oz and use a postage scale for the 3oz out of the third can.
I have weighed many 12oz cans full and empty and always come up with 12 oz difference so its pretty accurate. I have not lost a compressor yet doing it this way over the years before I had a pro charging station.

 

[dlundblad]

Originally Posted By: Trav
Put 2 12oz cans in (make sure the get the pure refrigerant not with oil in it) that gives you 24oz and use a postage scale for the 3oz out of the third can.
I have weighed many 12oz cans full and empty and always come up with 12 oz difference so its pretty accurate. I have not lost a compressor yet doing it this way over the years before I had a pro charging station.





Where'd you end up finding this at?

How do you go about weighing out 3 ounces? I would guess the weight of the hoses would throw everything off.

 

[Trav]

I have AllDATA, FSM, Motor and Bently stuff here for most common makes and models. Sure the weight of the hose and can fitting add weight but that doesn't change. Find a stable place to place the postal scale so you can sit the can on it fully connected then zero out the scale (make sure its set on oz not grams), open the valve and let the 3 oz go in to the system then shut it off and disconnect.

The hose connection has a one way valve at the can fitting so it doesn't leak out. Some people with disagree but I always add 1 oz extra for what gets left in the gauge and hose after disconnect. Factory tolerance for over/undercharge is about 50 grams 1.8 oz so its not an issue. If you need help PM me.
I buy this stuff in a 30lb can but the 12oz cans are very accurate weight and cheap at $5 a can. Its pure with no oil or sealers.

https://www.amazon.com/Chemours-DuPont-Suva-134a-Refrigerant/dp/B00IO4EYMY

 

[exranger06]

Originally Posted By: dlundblad

How do you go about weighing out 3 ounces? I would guess the weight of the hoses would throw everything off.

The weight of the hose doesn't change as the can is sitting on the scale. Place can on the scale and note the weight of it, whatever it may be. This is going to include the weight of the can itself and the hose. Charge the system until the weight is 3 oz less than the weight you recorded. Done.

 

[wtd]

Originally Posted By: mk378
Always measure refrigerant by weight when charging into an empty system. The only way to know for sure you have the proper charge is to start from empty (vacuum) and put in the specified amount by weight.


This is what I always do. I don't try to recharge by pressures and I always start from an empty system. I use a 30 lb tank and a refrigerant scale to do mine. I also use some stuff called Nylog to coat the o-rings and threads of any joints that I open up to help prevent future leaks and to help the connections come apart easier the next time.

I also always replace the receiver/dryer and all o-rings in the system if possible and the compressor if it's the source of the leak. I also usually replace the condensor because most newer ones are almost impossible to flush and they usually don't cost much these days. I only want to do the job once.

 

[bchannell]

Originally Posted By: wtd
Originally Posted By: mk378
Always measure refrigerant by weight when charging into an empty system. The only way to know for sure you have the proper charge is to start from empty (vacuum) and put in the specified amount by weight.


This is what I always do. I don't try to recharge by pressures and I always start from an empty system. I use a 30 lb tank and a refrigerant scale to do mine. I also use some stuff called Nylog to coat the o-rings and threads of any joints that I open up to help prevent future leaks and to help the connections come apart easier the next time.

I also always replace the receiver/dryer and all o-rings in the system if possible and the compressor if it's the source of the leak. I also usually replace the condensor because most newer ones are almost impossible to flush and they usually don't cost much these days. I only want to do the job once.


Lots of good advise here. Certainly NOT the only way, but the best for anyone who's doing it as a DIY project.
Also, DO NOT coat the condenser with oil. Oil is only for the compressor. It is carried through out the system, but should remain in suspension within refrigerant. Coating any heat xfer surface, EVAP or condenser will reduce its ability to remove or reject heat.

 

[Trav]

http://www.underhoodservice.com/ac-oil-service-avoid-compressor-failure/

AC Delco

 

[dlundblad]

Thanks for the info Trav.

Now I have some bad bearing noise that I am trying to pin down. Since everything has to come off, I want to replace my water pump (I hope this is the culprit), but this doesn't leave the compressor pulley out just yet. My e fan hasn't worked in quite a while either so I might as well do that while my front end is apart too.

I need to just take the belt off and wiggle stuff around.

 

[Trav]

Have you checked the relays and A/C pressure switch? You can use a test light and jumper its easy enough.