How much A/C oil to add after evacuating system
 

Hi All,

I think my 1990 F150 may have a leak in the R-134a converted A/C system. I'll verify w/a sniffer and gages I borrowed from a friend.

Meanwhile, my question is: If I have to evacuate the system completely in order to fix the leak, how much oil do I add back in the system? I'm sure some of the oil will probably remain in the system even after evacuating it, but not sure how much. I suppose I'd rather have a little too much oil than not enough.

Thanks,

Matt

*deleted* (changed my thought, sorry)

I just did this a few weeks ago on our '97 Mustang GT. I used a small R-134a Oil Charge that contained 1 oz. of refrigerant and 2 ozs. of PAG oil. That should be plenty.

According to my manual it is not required to add oil for an evacuation/recharge but I like to add a little...

It is not normal to add any oil for just a evac and recharge.

From when I was working in the truck shops, we only added oil if we changed a component out. There was always a certain amount we added per component changed but I don't remember off hand what each one called for.

don't know if anybody is interested but I have been finding some cool info on A/C systemcharges which includes oil charges. The Ford light truck charts run from 87-97

http://www.mastercool.com/media/temp_pressure_chart.pdf

Like I stated before, my manual shows no oil needs to be added. But I have always added a few ounces when I do an evacuate and recharge. There are more than a few Ford TSBs out there regarding too little oil in the A/C system leading to compressor failures. It's not that often I have ever pumped down a system more than once for any vehicle I have ever owned over the years, so it's not like I add oil at frequent intervals.

i completely agree with you rla. Unless you are changing the compressor there is no need to add a full charge of oil. Just a few ounces when you change a part out like a drier or a condensor only because it will have about that much in hanging out in the part you are changing.

Ok, you guys backed up everything I wanted to say but I figured I should wait. You add 1 or 2oz of oil for every component that is new. If the components stay in the vehicle, they will (should) have oil in them and you dont need to add more. Even if you got something (like a compressor) from somewhere else, itll probably still have oil in it. Just add a refrigerant charge and you should be good to go.

Here is the TSB rla2005 was talking about.
Attachment 24460

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I remember on some of the older compressors there was a plug you could take out after discharge & measure the amount of oil in the compressor , some had a dip stick , this was the 70s though , been along time ....Lew

You are showing your age Lew!


I remember those too!

We are just a bunch of old farts !!!

Well guys, the "old farts" as you put it are the guys with the knowledge because they have been there and done that. My hats off to them because I have learned a lot from them.

Thanks a bunch for the answers, guys. It sounds like it's pretty unanimous that I shouldn't need to add any oil into the system if I evacuate it, as long as I am not changing out any components. If I find there is a leak, hopefully it will just be an o-ring, and won't require component change-out.

By the way, I forgot to mention the truck has been converted to R-134a, but I doubt that makes much difference to your answers.