I need to replace myh compressor, but need to know a couple of things first.

When I replace the compressor, what is the oil I should use to put in the compressor. I have some that is PAG-150, is that what I should use?

Also, I was told I need to evacuate the system. Whst does that mean, and can I do it myself? or do I need a machine to do it??

 

AC is VERY VERY picky.. you need to do it right in order for it to work correctly. I always recomend that you have a pro do it but if you wanna do it yourself I can help. yes you need to have it evaced at a shop before you ever think about opening the system.


first off what kind of system is it. R12 oe 134A (although I am sure it;s 134a)

if it is yeah PAG150 is good. you need about 9 ounces of it for the compressor.



lemme ask you this. why do you need a compressor? did the old one lock up or just leak ? this is important. if it locked up there are a lot of steps you need to think about

 

I just replaced my compressor recently. I did not have it evacuated, but remember, anytime you discharge and open the system up, you will need to replace the receiver drier. Also, when you add new oil to the system, don't add it all to the compressor, put about 2/3's in the compressor and put the rest in the receiver drier and into the condenser. That will ensure that the system is well lubricated the first time you run it. I also just added 2 cans of freon 134a, reset the pcm, and it fired right up. Gets very cold now.

 

Please don;t take offence but thats not really correct.. the only part of the system that needs oil IS the compressor. adding it to the drier will just make it harder for the drier to aid in moisture absorbtion. The compressor is a working componant and needs oil like an engibe does or it will lock up. This is why you add the oil to the compressor. it will in time spread through the system anyway includig what is already in the system. when you add oil to teh comp you add it to the low side/suction port and once you get teh systeom closed down again you must turn the compressor by hand to prime the compressor..


Liek I said, there are a lot of little things that must be done. some people have luck with theres but that is all that it is. like I said. it;s very very picky

 

The reason you add oil to the receiver drier is analagous to adding oil to a K & N filter. It helps trap and hold the moisture. Plus it helps trap any loose pieces of dessicant in the receiver drier (that may have come loose in shipping, installation, etc) so they do not go flying around the system when you first start it up after replacing it.

 

if there is any desicant in the drier it;s faulty and will just end up cloging the H valve.


think of it this way.. the open system will have some moisture. when you finsih the system the the drier will go to work clearing the system. then when you pull it down to vacuum it will take care of the rest. (you did vacuum your system right?) Then as soon as you start the car and run the acwhile you charge the oil will get into teh drier anyway.. this way you start the process compleatly void of moisture

 

yes it is 134a, the compressor didn't lock up, it just started leaking. I wasn't sure why it was blowing hot air, so I tried to recharge the system, and it all started to spray out of the front of the compressor.

So I don't need to evacuate the system? Just replace the compressor, and fill it with refrigerant? (sp?)

 

ok. so you fell victem to the GM compressor front seal leak. you are not alone. this is good. this means that the system is still clean and the steps that you must take are no where near as long as if it locked up.


Yes, you have to have the system evacuated at a shop (unless it;s empty from teh leak) take off the cap that you used to fill it and poke the core and see how much pressure is in there..


after that you can remove the compressor. fil it with oil. put it back on. rotate it like I said above and then you can move on.

Since you will ahve the system open I HIGHLY remomed that you replace the drier. along with any o rings that you disturbed when you roved everything.

once thats done you have to take it back to a shop where they will put the system on a vacuum for about a half hour. this does 2 things. 1 it will pull all the moisture out of teh system and 2 it will tell them if there are any large leaks (if you forgot to tighten somethinng or messed up an o ring)


then. you can charge it, witch again should be done at a shop with a real set of gauges but you can get by with just adding the amount listed on the stock drier or AC system sticker under the hood. usual sometining like 2 pounds. you figure this by the formula

16 ounces = 1 pound

refrigerent is usualy 12 ounces

so take 16 ounces X 2 pounds = 32 ounces

32 ounses divided by 12 (for the can ounces) =2.666666 cans.


just put in how ever many pounds the system calls for to figure this out

 

ok great, thanks! any other tips or advice? How hard is it to change compared to changing the spark plugs?

 

PAG 150 is what I used. I also lowered front sway bar out of the way to make removing compressor easy. I also bought a vacuum pump from a pawn shop and evacuated system myself but with the warmer weather right around the corner they are going to be getting hard to find at the pawn shops. I replaced compressor, dryer, and expansion valve-block. Added 4 oz. of oil to compressor when I did it. Not an expert here but thats my story.

 

my ac also crapped out last summer. hopefully it just needs to be recharged and its not a leak. my question is where do you found out which ac system you have?

 

you used a vacuum pump to release the pressure in the system? The idea of ecacuation is to collect and contain the freon in a proper container not vent it to atmosphere witch is what teh cac pump does.. it;s not a "horrible" think to do with 134a since it is "ozone friendly" but the EPA would still shake there finger at you for that

 

you will see it on a sticker under the hood or on the stock drier telling you the type and amount of freon it holds. what is your system doing? did it just stop working or is it cycling on and off?

 

What I meant was vacuumed moisture and air from system, not totally evacuate. Sorry.

 

but would you say it is easier or harder than changing the spark plugs?